This will be the spot for questions about building the Tiny Giant (http://www.diystompboxes.com/smfforum/index.php?topic=89233.0). Questions, discussion, mod ideas, and build reports will go here. Here's my prototype build. I have a few ideas for another one I want to build, this one with 2 of the boards for stereo and some EQ.
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=44014&g2_serialNumber=2)
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=44017&g2_serialNumber=2)
Quote from: thedefog on February 02, 2011, 11:31:31 PM
Hey Taylor,
Thanks for the kit! I got it tonight and built it up. The board is top notch quality too! I tested it out with my gateway's generic power supply and on my twin reverb's speaker cab. I'm amazed at how loud it gets. Pretty impressive! Only thing now is that I have a buzz on it that I have to debug. It's got to be due to the crappy power supply I'm using, so I'm thinking I'm gonna just grab a hold of a 24vDC transformer at 4A and build a power supply myself with some decent filtering caps. I know that sorta goes against the tiny factor of it, but I intend to building it into a super small home-made combo amp cabinet 1x12 with a tone stack and the tiny tremolo circuit for fun.
http://cgi.ebay.com/24V-5A-TRANSFORMER-BRAND-NEW-BLOWOUT-SALE-PRICE-/330517526923?pt=LH_DefaultDomain_0&hash=item4cf461398b
That one looks cheap enough to try out. I shouldn't have to change any resistors with the 24 volts on the regulator, correct? Should I worry about excess heat?
I'm also using a cheap power supply and I have no hum, so I don't think you need to go as far as adding a transformer. I suspect you have some kind of ground loop or ground issue. How exactly do you have it built now? Is it in any kind of enclosure? If so, is the enclosure grounded? Have you taken care not to connect the sleeve of the speaker jack to ground as shown in the PDF?
Also, let me know if you had any questions that the PDF did not help with while building it.
I'll take a picture of my build. I don't have an enclosure yet. I'm just testing out the input with banana jacks currently, and have temporary speaker and power jacks wired. I did notice though that my power supply was emitting a ultra high pitched squealing sound when it is plug into the wall. I'll get a hold of another laptop power supply to test with and post my results here.
I just ordered this power supply: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=130343776062&ssPageName=STRK:MEWNX:IT
I will post my results when it arrives. I needed one anyway, and $8.00 was cheap enough to test, and it doesn't hurt to have a back-up power supply for my laptop anyway.
I meant alligator clips. Don't know why I said banana jacks... Must have been looking at my soundlab synth.
Anyway, your PDF looked great Taylor. I had absolutely no issues building it, and it is all very well marked.
In the meantime, I'm looking into active eq and running a tiny tremolo circuit as well. I like your idea for stereo, I can imagine the possiblilties for stereo effects. A nice stereo ping-pong vibrato like that on a Rhodes piano with the bass and treble swapping sides alternately would be amazing.
Quote from: waltk on January 26, 2011, 09:35:12 PM
QuoteIf those are the Swiftech MC14 sinks, they are only rated for 5watts... I'd be concerned about not having enough heat sink in this situation.
TDA7240 is 65% efficient. So if it is puting out 10 watts (which is about the max into an 8 ohm load without too much distortion), then it will consume 15.38 watts. That leaves 5.38 watts to dissipate as heat.
Dissipation in a Class B amp is greatest BELOW maximum power output. At FULL signal, power comes in and goes out. At half power, a little less power comes in but much less power comes out.
Somewhere in that sheet is a curve showing dissipation peaking near 8 Watts at part power.
I'm not real concerned. Experience with FTC testing which holds an amp near maximum heat for many minutes proves that real-world dissipation is usually MUCH less, even in stage-amps. If you do skate too close to the edge, the chip will shut-down, you feel it and burn your finger, you have a clue to get a bigger sink.
CLEAN power in 16 ohms is 6 Watts (maybe 8W the way car and gitar amps are specced). There's probably a simpler path to 6 Watts in 16 ohms.... and maybe not, since Taylor's kit is so neat.
NewEgg specs:
"C/W: 9.0 (including TIM joint)
Maximum recommended heat load: 5 Watts per heatsink"Taking the first number: 8 Watts at 9 deg C per Watt is 72 deg C rise above ambient. On older discrete audio-amp devices we liked to stay below 50 deg C rise..... but seals and dice have improved a LOT, and the on-die thermal shuts-down on short-term events we may never have known about in the days of mercury thermometers.
The 5W at 9C/W or 45 deg C seems very conservative when this is the major heat-load in the box, but may be appropriate when you have a hot CPU and too much other stuff jammed into a small PC.
What sort of power supply would one need to build two of these into one enclosure and use a stereo input jack? Just wondering :D
I'll be doing just that pretty soon, so I will report if I have any trouble using a standard 19.5v/4amp supply for 2 boards. My suspicion is that the chip isn't going to actually draw 4 amps of current, but I have seen some supplies on ebay with 7 or 8 amps if that is indeed needed.
Just received by PCB and kit last night - stunning quality. At first I thought the PCB was missing - it's that small I could barely feel it in the padded envelope it shipped in!
Built it up in <30 minutes, just waiting for my power supply to arrive now.
I've added the Tiny Giant to the Wiki under Pedal Specific Info -> Amps -> Tiny Giant (http://www.diystompboxes.com/wiki/index.php?title=Tiny_Giant (http://www.diystompboxes.com/wiki/index.php?title=Tiny_Giant)).
Rob.
Hi Rob, thanks for adding it to the wiki - I haven't really looked at that and kind of forgot that it existed!
Taylor,
I'm probably going to order a kit here soon. I'm planning on putting it in a large enclosure so I can put it together with several pre-amps. Would I still be fine using the chassis as a heat sink or should I get a separate heat sink? I'm planning on making the chassis from scratch using sheet metal.
Edit: I also have a laptop power supply that I don't use any more. It's older but is 19.5v but at 3A. If my calculations are right, it comes out to 58.5W of power which means it SHOULD work with the amp right?
Using a bigger enclosure is even better for heat dissipation. Just be sure to keep the regulator's heat sink tab electrically isolated from the enclosure as per the PDF.
That laptop supply should be fine.
Hi, just subscribing to the thread. I'm waiting to see how you get on with stereo with this Taylor. One of the other boards I got from you is earmarked for my reverb plate to replace the ruby. Thanks for the project.
Ah, very cool. I was hoping we'd see these turn up in some uses beyond straightforward amplification. I'm building a spring unit right now, but a plate would be quite nice - I'd like to build one at some point. Shame I can't think of those wonderful plate reverb sounds of the 60s without my mind instantly going to Phil Spector on trial...
Quote from: ralley on February 04, 2011, 08:00:03 PM
Just received by PCB and kit last night - stunning quality. At first I thought the PCB was missing - it's that small I could barely feel it in the padded envelope it shipped in!
Built it up in <30 minutes, just waiting for my power supply to arrive now.
I've added the Tiny Giant to the Wiki under Pedal Specific Info -> Amps -> Tiny Giant (http://www.diystompboxes.com/wiki/index.php?title=Tiny_Giant (http://www.diystompboxes.com/wiki/index.php?title=Tiny_Giant)).
Rob.
Yup the kit Taylor put together is great. The PCB is top notch, and all the components are perfect and perfectly spaced for the board he sells. Thanks again Taylor for putting this project together. As soon as I settle on a tone stack that I like it is getting built into a mini amp for practice/backup.
Quote from: Taylor on February 05, 2011, 05:05:52 PM
Using a bigger enclosure is even better for heat dissipation. Just be sure to keep the regulator's heat sink tab electrically isolated from the enclosure as per the PDF.
That laptop supply should be fine.
Awsome. Now I just gotta figure out how big of an enclosure I want and go get a piece of sheet metal. Not sure if I want to use steel or aluminum. Aluminum would probably be a bit easier to work with but steel would be much stronger I would imagine.
I totally forgot about this project!
Just ordered a PCB/kit. Great work, Taylor.
I was just thinking, though, that maybe a power on/off switch would be more useful (for me) than a standby switch. For amps, I like to be able to turn them off without resorting to unplugging them...even for a really small amp.
I'm assuming that using a SPST switch between the positive (or negative) power supply lead and the PCB will do the trick?
Yep, that will do it. I should add something about that in the project. I somewhat enjoy the ritual of standby, then power, so I'll probably have both in my bigger version. Plus it keeps speaker pop from happening, I suppose. Thanks for the props - I'm happy about how this turned out.
Quote from: Taylor on February 06, 2011, 06:59:26 PM
I somewhat enjoy the ritual of standby, then power, so I'll probably have both in my bigger version.
Yeah, me too. That's what I was thinking. It's like a little tube amp if you have power and standby. ;D
I ordered my kit last night. The concept of putting an amp right on my pedalboard is something I just CANNOT pass up! My wife actually PUSHED me to order it. I guess she doesn't think I can do it...
Anyway, I'm looking at the power supply that "thedefog" identified. What I would like to know is, what kind of female connector is required to receive that plug? Surely not a Boss? Where can I get one?
QuoteAnyway, I'm looking at the power supply that "thedefog" identified. What I would like to know is, what kind of female connector is required to receive that plug? Surely not a Boss? Where can I get one?
There are other power supplies that are as good/cheap. Search for "IBM 16V 4.5A" on Ebay, and you'll find hundreds. Taylor has updated the build documentation recently, and he's suggesting a laptop power suppy from 15-20 Volts. The reason that less voltage (within that range) is better is that any extra power supplied to the board must be dissipated as heat by the onboard voltage regulator.
I'm not sure what size plug they are using, but I found it easier to cut the plug off and attach a standard Boss type plug anyway (2.1mm X 5.5mm - inside, outside). That was my preference because I already have a stock of that size plugs and jacks.
I see. That takes care of the low-hanging fruit. Thanks for the insights, Walt. I'll check out the power supply you indicated.
Now for the next set of questions. In the build instructions, there are two paragraphs that seem like they might conflict. If you intend to use the case for heat sinking purposes, would you not WANT the amplifier and regulator ICs to be mounted directly to the case? Especially if you use a plastic jack for the speaker cable? I thought also I should use a plastic jack for the audio input, although that throws me into a tizzy about grounding.
Anyone got any ideas how to sort this out? And also, how would one tie into the amp circuit to provide external power -- like to a pedalboard? I was actually thinking I could connect a 9V regulator and some capacitors to the external power connections and run it to two binding posts inside the amp case. I could then connect a series of power cables with male Boss connectors on one side and rings on the other to attach to the binding posts. This way, I get an amp AND a power supply AND a distribution bus AND only one power cable coming to the pedalboard.
QuoteNow for the next set of questions. In the build instructions, there are two paragraphs that seem like they might conflict. If you intend to use the case for heat sinking purposes, would you not WANT the amplifier and regulator ICs to be mounted directly to the case? Especially if you use a plastic jack for the speaker cable? I thought also I should use a plastic jack for the audio input, although that throws me into a tizzy about grounding.
The amp IC has its heat sink tab internally connected to ground, so attaching it to the enclosure both grounds it electrically and provide a good heat sink (a desirable thing).
The voltage regulator has its heat sink tab internally connected to the V+ output - so you MUST NOT connect it to ground. That's why Taylor provides the special bushing with his kit; so you can physically attach the voltage regulator to the case for heat sinking purposes, while keeping it electrically isolated.
Because of the design of the chip amp, you don't want the speaker outputs connected to ground - or anything else.
Your plan to use the power supply for multiple purposes will work fine (I've done it). You could actually power the rest of your pedalboard off of the same laptop power supply. Depending on how big your pedalboard is (how much current your pedals draw collectively), you could do it with an LM7809 (1 amp), LM317 (1.5 amp), or LM338 (5 amp).
David, some of your questions are covered in the PDF. Check it over a few times to get familiar with some of the details of the project, w.r.t. grounding especially.
Quote from: David on February 07, 2011, 06:08:56 AM
I ordered my kit last night. The concept of putting an amp right on my pedalboard is something I just CANNOT pass up! My wife actually PUSHED me to order it. I guess she doesn't think I can do it...
Anyway, I'm looking at the power supply that "thedefog" identified. What I would like to know is, what kind of female connector is required to receive that plug? Surely not a Boss? Where can I get one?
Hey there,
The type plug used on the supply I bought fits into a 2.5mmx 5.5mm, so the boss-style won't work. Radioshack sells these though, and that's what I wired it up to.
I was going to build an enclosure for this mini-amp, but realized that I suck with wood-working and that it would probably look like total crap. Good thing I had my dad's busted TEAC Reel-to-Reel sitting nearby. I made a speaker baffle from a piece of scrap wood and dremeled out a circle, mounted the speaker, and fit it right inside the TEAC. It even has a little side-pocket where the input.output controls used to be for guitar input/volume/tone. :)
Taylor.... If I have the preamp, do I still need TL072 as you schematic.?
You can skip it if you want. But I find it easier to just build it stock. You don't gain anything by bypassing the buffer, and it's cleaner (the wiring I mean) and only like 50 cents in parts, but that's just me.
Quote from: Taylor on February 09, 2011, 07:27:18 PM
You can skip it if you want. But I find it easier to just build it stock. You don't gain anything by bypassing the buffer, and it's cleaner (the wiring I mean) and only like 50 cents in parts, but that's just me.
Taylor...thank you. I will buy the stock board and try it
Resistors
all 1/4 watt
1 – 100k Brown, black, yellow,
1 – 220k Red, red, yellow,
2 – 1m Brown, black, green,
2 – 2.2R Red, red, gold,
[Marked "2R2" on the board - this is 2.2 OHMS]
1 – 1k Brown, black, red,
1 – 120R Brown, red, brown,
is this correct?
Hey guys,
I got the new power supply the other day and finally got around to testing it with the amp. It wasn't the source of my buzzing noise unfortunately...
I double checked with the schematic and tested my voltages, which all checked out good. All grounds are going to where they need to, and my heatsink is not shorting to the back of the V+ regulator. I reflowed solder in case I had any cold joints (doubtful) and triple checked my wiring. Also rechecked resistor and cap values and orientation. All checked out good. The buzz gets louder as I turn the guitar volume down. With no instrument plugged in, it is a very loud buzz. When I ground the input wire, it completely goes away. When I remove the TL072 out of the socket, there is only a faint buzz present. I tried different TL072s as well as other dual opamps and it didn't help. Something is up with the input buffer stage, only all my grounds and part values are correct. ???
Quote from: rotylee on February 10, 2011, 11:49:09 AM
Resistors
all 1/4 watt
1 – 100k Brown, black, yellow,
1 – 220k Red, red, yellow,
2 – 1m Brown, black, green,
2 – 2.2R Red, red, gold,
[Marked "2R2" on the board - this is 2.2 OHMS]
1 – 1k Brown, black, red,
1 – 120R Brown, red, brown,
is this correct?
Yes, that's right. Do you have a multimeter? It will be incredibly helpful to you on this build (checking ground continuity as mentioned in the PDF in addition to checking resistor values).
Quote from: thedefog on February 10, 2011, 08:16:32 PM
Hey guys,
I got the new power supply the other day and finally got around to testing it with the amp. It wasn't the source of my buzzing noise unfortunately...
I double checked with the schematic and tested my voltages, which all checked out good. All grounds are going to where they need to, and my heatsink is not shorting to the back of the V+ regulator. I reflowed solder in case I had any cold joints (doubtful) and triple checked my wiring. Also rechecked resistor and cap values and orientation. All checked out good. The buzz gets louder as I turn the guitar volume down. With no instrument plugged in, it is a very loud buzz. When I ground the input wire, it completely goes away. When I remove the TL072 out of the socket, there is only a faint buzz present. I tried different TL072s as well as other dual opamps and it didn't help. Something is up with the input buffer stage, only all my grounds and part values are correct. ???
Hmm. I'm not an expert on switch mode power supplies, but my assumption was that, with the switching action and regulation in the supply, then regulation on the amp board, there would not be much chance of 60 cycle hum coming from the supply. So this leads me to think that the hum is coming from another source and being coupled through the signal grounds. Do you still not have it boxed up or shielded at all? I never built one that wasn't in an enclosure, but that seems like it could contribute. Any other parts of the puzzle you can provide - what kind of guitar with what kind of pickups for example.
I will think some more about what might be happening and get back if I can think of anything.
I'm running it outside of an enclosure, no shielding, so that probably explains a few things. I'll triple check my continuity to ground everywhere again just to be sure, especially on the input buffer stage. I'm using my tele with a humbucker in the bridge, and the noise doesn't really change much in volume between the HB and single coil. It is quite in my other tube amps.
Shielded input cable may help my cause a little here, I'll try that out and see if it helps. It is definitely 60hz hum I'm getting.
I made a mounting plate for the input jack, power, volume, and a tone stack (BMP) into cabinet I am using, and that pretty much took care of all the cyclical hum I was getting.
Cool, glad to hear that it's sorted. I had a feeling some shielding would do the trick.
Got my power supply ordered off Flea Bay !!! TG kit on the way ... Very exciting !!! :icon_mrgreen:
Quote from: StarGeezers on February 13, 2011, 08:02:07 AM
Got my power supply ordered off Flea Bay !!! TG kit on the way ... Very exciting !!! :icon_mrgreen:
LOL now your gonna be banned from SEwatt
How are the Stargeezers doing this year ?
You actually live close to Taylor ,same area at least.
You still using your Croaker amp ?
Is this a good ps?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270607079418
Yes, that looks good.
Quote from: Taylor on February 07, 2011, 02:24:26 PM
David, some of your questions are covered in the PDF. Check it over a few times to get familiar with some of the details of the project, w.r.t. grounding especially.
I got it. Closer reading did the trick. I also got my kit today. Excellent workmanship! Now, some more questions:
1) I am not familiar with soldering to a board with little grommet-like things like this one has. I presume I simply solder to the grommets?!? Is a special soldering tool required? I have the standard 25W small soldering iron. It has a point, but I'm not sure how well it will get into those grommets... Also, I presume the components will go on the silkscreened side of the board?
2) Since I am planning to draw power from the specified connector to feed my pedalboard, I got a castoff power supply from the local computer store that puts out 5A so there's an amp or so available to my pedals. Unfortunately, this supply delivers something like 18 volts, but my amp is going into a RACO box. That should be enough metal to keep the temp down, right? Would I get the ground connection from the point where the power supply ground connects to the amp board?
Hmm, if I understand you correctly, the "grommets" are just the regular holes that the parts go in like any other PCB. If you're used to single-sided boards etched at home, the difference between that and these is that these are "plated through holes". The pad that you would solder to on a single-sided, home-etched board is still there, but the inside of the hole has metal plated into it to make a better connection, and so that you can solder from either side of the board, and to connect the top and bottom copper layers.
But you can solder to it just like any other kind of pcb. No special tool is required. You don't need to get the iron inside the hole, just heat the pad and component lead as you normally would with any PCB.
You'll be fine with an 18v supply. I'm using a 19.5v one and a box smaller than a standard RACO.
Your ground connection for pedals should probably be the ground tab on your power inlet jack.
Quote from: Taylor on February 14, 2011, 11:26:46 PM
Hmm, if I understand you correctly, the "grommets" are just the regular holes that the parts go in like any other PCB. If you're used to single-sided boards etched at home, the difference between that and these is that these are "plated through holes". The pad that you would solder to on a single-sided, home-etched board is still there, but the inside of the hole has metal plated into it to make a better connection, and so that you can solder from either side of the board, and to connect the top and bottom copper layers.
But you can solder to it just like any other kind of pcb. No special tool is required. You don't need to get the iron inside the hole, just heat the pad and component lead as you normally would with any PCB.
You'll be fine with an 18v supply. I'm using a 19.5v one and a box smaller than a standard RACO.
Your ground connection for pedals should probably be the ground tab on your power inlet jack.
Excellent to all the above. Exactly the answers I was hoping for.
Taylor , got my Kit !! What a Beauty , and TINY ... :icon_eek: Very COOL !!! :icon_cool: This just looked like too much FUN to pass up !!! Thanks , Dude !!!
Brymus Possibly :icon_surprised: ... Doing Good , got a CD ... Surprisingly very Close to Taylor ... Yes , still Croaking ... :icon_mrgreen:
Got mine today as well. Can't wait to get it going. :)
I'm noticing on mine that there is some very low level distortion going on, even with the guitar volume rolled down and volume on the amp low. Where could something like that come from if it isn't dependent on the input volume?
The distortion really is the same regardless of input volume, or it's there at any input volume (but more distorted at louder in volume)?
Taylor, I still have to connect the "offboard" components on mine.
What I need to know is, how much current can the "offboard connection" really supply? Can it go to an amp?
If not, I can always use a 9V wall wart like I do now. I had thought about feeding the "offboard connection"
through a LM317 set up to deliver 9V.
It would sure be nice to just have one power cable coming to my pedalboard.
The onboard voltage regulator has a max current capability of around 5 amps as I recall, but check the datasheet. Assuming your power supply puts out that or more, the current available for pedals would be that minus the actual current draw of the amp. I haven't had a chance to measure current draw yet, but I wouldn't be surprised if it was something like 3a or less in regular use.
Quote from: Taylor on February 17, 2011, 02:29:03 PM
The onboard voltage regulator has a max current capability of around 5 amps as I recall, but check the datasheet. Assuming your power supply puts out that or more, the current available for pedals would be that minus the actual current draw of the amp. I haven't had a chance to measure current draw yet, but I wouldn't be surprised if it was something like 3a or less in regular use.
So that pin that is marked for offboard connections in the build document does not connect to the half of the TL072 that is creating the bias voltage, then. OK, got it. EXCELLENT!!!!!!!!!!!!! THANK YOU!!!!!!!!!! :icon_mrgreen:
Just ordered Tiny Giant amp + Christine, can't wait. Thank you.
Quote from: Taylor on February 16, 2011, 01:54:35 PM
The distortion really is the same regardless of input volume, or it's there at any input volume (but more distorted at louder in volume)?
It's there regardless of input volume. Not more or less at different levels (unless it's cranked and it's breaking up obviously).
Hmm, that's quite strange. Generally, distortion means clipping. But I can't think of any normal way that something could clip where the amount of distortion does not vary with input volume.
Are you plugging your instrument straight into the TG? Is it a guitar or something else? If a guitar, is it a normal passive one?
Got mine built. A couple of naked box shots and the power adapter I'm using, $9.80 on eBay. I really dig this project. And it plays just fine with a 16 ohm cab.
(http://img835.imageshack.us/img835/2978/tinygiantguts.jpg)
Fiber isolation washer to keep the output jack, well, isolated from the chassis which is at ground potential.
(http://img406.imageshack.us/img406/4379/tinygiantjack.jpg)
$9.80 on ebay. VAIO Laptop 19.5V 4.7A from seller laptopz-outlet.
http://cgi.ebay.com/AC-Power-Adapter-Charger-fr-Sony-VAIO-Laptop-19-5V-4-7A-/310229426156 (http://cgi.ebay.com/AC-Power-Adapter-Charger-fr-Sony-VAIO-Laptop-19-5V-4-7A-/310229426156)
(http://img146.imageshack.us/img146/3913/tinygiantpower.jpg)
QuoteGot mine built.
It's beautiful. Nice work!
Ordered mine!
Gonna try it for monitoring with my mono reel to reel recording rig.
I'm working on testing mine now, which is proving interesting since my guitars are in the shop and I'm
trying to improvise using a signal generator. I had issues with the op-amp not being in all the way and
a faulty mute switch. I tracked these down and I'm going to put a different switch in.
What I'm noticing is that the 10K is not acting quite as I expected. It was marked 10K audio, so I don't
THINK it's linear, but it's not acting like it's logarithmic. I get nothing for probably a third of the pot's travel,
then the volume climbs like a Saturn V taking off.
Any ideas?
I think I'm going to build this in a box with one of those FET Fender blackface Preamps all in one box.
Not really a related question but say I wanted to use a MAX1044 to run that at 36V; the max the 1044 can take is 9V, right? Would I want to use a regulator for that, or just run a voltage divider into an op-amp buffer at the full voltage?
I don't think you can. http://pdfserv.maxim-ic.com/en/ds/ICL7660-MAX1044.pdf (http://pdfserv.maxim-ic.com/en/ds/ICL7660-MAX1044.pdf)
From the data sheet:
QuoteAbsolute Maximum Ratings
Supply Voltage (V+ to GND, or GND to VOUT)....................10.5V
It looks like you're limited to 10.5v, or we'll call it 10v input, and if I'm reading that right, 10v max output. It looks like they stack the Vout on top of Vin to get voltage doubling. I'd verify this information, I've not read the entire data sheet or really worked with this device.
There's a way to get 36V using diodes; it's on geofex.
You can get there with a charge pump, but I don't know what's happening on the current side of things.
Quote from: David on February 20, 2011, 10:17:45 PM
I'm working on testing mine now, which is proving interesting since my guitars are in the shop and I'm
trying to improvise using a signal generator. I had issues with the op-amp not being in all the way and
a faulty mute switch. I tracked these down and I'm going to put a different switch in.
What I'm noticing is that the 10K is not acting quite as I expected. It was marked 10K audio, so I don't
THINK it's linear, but it's not acting like it's logarithmic. I get nothing for probably a third of the pot's travel,
then the volume climbs like a Saturn V taking off.
Any ideas?
I was wrong. I fed it a bass instead of a Colpitts oscillator. Holy cow, Houston! We have an amp! Taylor, this thing is INCREDIBLE!!!!!!!!!!!!!!!!!!!!! I won't be able to use it this week because I don't have the pedalboard power takeoff yet. It should be ready to go next month. I CAN'T WAIT!!!!!!!!!!!!!!!!
Quote from: Taylor on February 18, 2011, 02:46:23 PM
Hmm, that's quite strange. Generally, distortion means clipping. But I can't think of any normal way that something could clip where the amount of distortion does not vary with input volume.
Are you plugging your instrument straight into the TG? Is it a guitar or something else? If a guitar, is it a normal passive one?
This is plugging straight in with my guitar, or anything for that matter. Just got a dirty signal. It's like 1/10th of the signal is noisy/distortion and the rest is clean, which leads me to believe I've got a bad component somewhere. I'm gonna try different TL0x2's as well as some other duals I've got laying around first.
Quote from: thedefog on February 22, 2011, 03:37:43 PM
This is plugging straight in with my guitar, or anything for that matter. Just got a dirty signal. It's like 1/10th of the signal is noisy/distortion and the rest is clean, which leads me to believe I've got a bad component somewhere. I'm gonna try different TL0x2's as well as some other duals I've got laying around first.
Have you checked that the supply voltage matches what it says in the PDF?
Quote from: Taylor on February 22, 2011, 03:43:25 PM
Quote from: thedefog on February 22, 2011, 03:37:43 PM
This is plugging straight in with my guitar, or anything for that matter. Just got a dirty signal. It's like 1/10th of the signal is noisy/distortion and the rest is clean, which leads me to believe I've got a bad component somewhere. I'm gonna try different TL0x2's as well as some other duals I've got laying around first.
Have you checked that the supply voltage matches what it says in the PDF?
Yeah and they all check out to what they should. I will re-check later tonight though. Something may have moved when I put it into the cabinet.
Just finished building my Tiny Giant. Works perfectly and is plenty loud. Did it all for $45.
kit: $20
hi-fi speakers from Goodwill: $10
Sony VAIO power source from ebay: $10
misc. hardware: $5
This thing is great--I wanted to build one to play background percussion tracks while performing and it will do that nicely.
Thanks Taylor!
Cool, post pics if you get a chance dylar.
yes, it looks like a set of speakers with a Radio Shack project box on top - because that's what it is. Cost effectiveness was my main concern. Not pretty but works great!
(http://i54.tinypic.com/w0p4br.jpg)
(http://i52.tinypic.com/rwsaid.jpg)
> I haven't had a chance to measure current draw yet, but I wouldn't be surprised if it was something like 3a or less in regular use.
Assuming 4 ohm load and about 12V regulated voltage to the TDA7240 chip: 2 Amps near-clipped sine-test-tone, 3 Amps maxxed-out utterly-clipped (LOUD!!).
On 8 ohms, 1-1.5A; on 16 less than 1A tops.
At sine-clipping in 4 ohms, the total heat in the box is 18V*2A= 36 Watts in, ~~20Watts delivered to speaker, 36W-20W= 16 Watts of heat in the box. (Similar when maxx-overdriven... more power in but even more power to speaker, about 18W heat in box.) This is a lot of power for these small boxes. They will get HOT. Too hot? Apparently not. If overheated, these chips will shut-down and re-start when cooler. If it craps-out under abuse, and chips are HOT, re-check chip thermal contact to case (flat, smooth, greased) then ponder a larger case or higher-impedance load (and less power out).
These calcs are worst-case. Many players won't come close to these numbers; it may be hard to approach 3A demand with actual fingers and speakers. I think typical heat is 5 to 10 Watts, the box will run very-warm not HOT.
Since you have a 4A-7A regulator and 4.7A cord-warts, there is at least another 12V 1A which could be stolen for pedals, direct or via a 9V regulator. That's ample for any pedal which does not need a dedicated wall-wart.
> the half of the TL072 that is creating the bias voltage
The unused side of TL072 is just UN-used. Not even "creating the bias"; no real reason to do that. Taylor connected it as follower and nailed the input to +12V, which just slams it into a "do nothing" state so it won't make trouble. (TL071 could be used, but is less common and no cheaper.)
Distortion? Measure voltages. There's a troubleshooting thread somewhere.
Quote from: PRR on February 22, 2011, 08:20:31 PM
> I haven't had a chance to measure current draw yet, but I wouldn't be surprised if it was something like 3a or less in regular use.
Assuming 4 ohm load and about 12V regulated voltage to the TDA7240 chip: 2 Amps near-clipped sine-test-tone, 3 Amps maxxed-out utterly-clipped (LOUD!!).
On 8 ohms, 1-1.5A; on 16 less than 1A tops.
At sine-clipping in 4 ohms, the total heat in the box is 18V*2A= 36 Watts in, ~~20Watts delivered to speaker, 36W-20W= 16 Watts of heat in the box. (Similar when maxx-overdriven... more power in but even more power to speaker, about 18W heat in box.) This is a lot of power for these small boxes. They will get HOT. Too hot? Apparently not. If overheated, these chips will shut-down and re-start when cooler. If it craps-out under abuse, and chips are HOT, re-check chip thermal contact to case (flat, smooth, greased) then ponder a larger case or higher-impedance load (and less power out).
These calcs are worst-case. Many players won't come close to these numbers; it may be hard to approach 3A demand with actual fingers and speakers. I think typical heat is 5 to 10 Watts, the box will run very-warm not HOT.
Since you have a 4A-7A regulator and 4.7A cord-warts, there is at least another 12V 1A which could be stolen for pedals, direct or via a 9V regulator. That's ample for any pedal which does not need a dedicated wall-wart.
> the half of the TL072 that is creating the bias voltage
The unused side of TL072 is just UN-used. Not even "creating the bias"; no real reason to do that. Taylor connected it as follower and nailed the input to +12V, which just slams it into a "do nothing" state so it won't make trouble. (TL071 could be used, but is less common and no cheaper.)
Distortion? Measure voltages. There's a troubleshooting thread somewhere.
Sorry. My mistake. It looked like it was generating Vbias. In any case, mine is working just fine. Now I have to get the secondary power supply working.
Finished my Tiny Giant this weekend, it is indeed plenty loud. (Pics to follow later this week)
At first I thought I had some kind of overdrive going on when going past 9:00 on the (25k) volumepot, but that's only the case when I plug the guitar direct into the amp: going over 9:00 will not output more volume, only more distortion. But with a pedal in front I get waaaay more volume, although I still can't get over 9:00 with the volumepot. Haven't measured the levels yet, as far as I can see the TDA clips at that point?
Anyway, two things in the build pdf v2 caught my eye:
QuoteBefore you power the TG up the first time
-Use your multimeter set to continuity test mode, to verify that neither terminal of the speaker jack is connected to ground.
-Use your multimeter set to continuity test mode, to verify that the heat sink tab of the LM338T is not connected to ground.
-Use your multimeter in voltage mode to test the voltage at pin 8 of the TL072. It should be approximately 11.6 volts.
That last point is not possible *before* powering up :icon_confused:
QuoteRaise the 1k to: 1.2k 1.5k
the output voltage becomes: 13.75v 16.88v
the power becomes: 20w 24w
But wasn't 'stock' (1k) supposed to be 20W already?
All in all I'm very happy with this project, I'm pondering building a few more!
Quote from: pruttelherrie on March 08, 2011, 04:39:20 PM
Finished my Tiny Giant this weekend, it is indeed plenty loud. (Pics to follow later this week)
At first I thought I had some kind of overdrive going on when going past 9:00 on the (25k) volumepot, but that's only the case when I plug the guitar direct into the amp: going over 9:00 will not output more volume, only more distortion. But with a pedal in front I get waaaay more volume, although I still can't get over 9:00 with the volumepot. Haven't measured the levels yet, as far as I can see the TDA clips at that point?
That could be, it depends largely on what kind of instrument you're using. The amp is designed with some boost in the preamp section, to accommodate a variety of inputs, from weak to hot guitars, piezo-equipped acoustic instruments, etc. So for example my cello with piezo element is much quieter than my active bass - I can turn up the volume half way with the cello with no sign of clipping.
Quote
-Use your multimeter in voltage mode to test the voltage at pin 8 of the TL072. It should be approximately 11.6 volts.
That last point is not possible *before* powering up :icon_confused:
You're quite right about that. Thanks for bringing that error to my attention.
QuoteRaise the 1k to: 1.2k 1.5k
the output voltage becomes: 13.75v 16.88v
the power becomes: 20w 24w
But wasn't 'stock' (1k) supposed to be 20W already?
The thing is that wattage ratings are - always, by everybody - an estimate or average or a shrug. In precision test applications, an amp must be measured at some incredibly tiny total harmonic distortion to find the "wattage" rating. For guitar, the standard is to measure at some
much higher level of distortion and call that the wattage. So for example, the EHX 22 caliber is claimed to be a 22 watt amp, but I calculated at some point that it's not possible for it to be 22 watts except by a very lenient definition of watts.
Then you have DJ equipment and car stereos which are rated by a standard invented by some truly magical thinkers: this equipment is measured by the absolute biggest peak it can put out, with some monstrous amount of distortion. So you have car amps not much more powerful than the Tiny Giant, being rated at like 900 watts or something else ridiculous.
The amp chip in the Tiny Giant, the TDA7240A, is called by the datasheet, a "20 watt amplifier" - so that's why I've called it that in the literature. In reality, depending on supply voltage and the impedance of the speaker you plug into, it's a 12-24w amplifier. 20 watts is an average since I can't know how you'll hook it up beforehand.
Audio amp ratings aren't standardized, so there's no way to be objective about it, unfortunately. I do hope that the chart at least shows, in an understandable way, how to make it louder by changing the resistor.
Another thing to point out is that double wattage is not twice as loud, only 3db louder, which is on the edge of perceptibility. In other words, don't stress too much about watts. To get twice as much volume as this amp can do, you'd need 200 watts, and no resistor change will get that out of this design, so if something in the range of 15-24 watts is not enough, a 3886 amp would be the next step up.
The ground wire from the input jack to the PCB had come a little loose and was the source of the distortion and 60hz hum in my build. I have my jack plate grounded, so the jack was grounding at the plate and not directly at the point on the PCB. As soon as I re-soldered it, it went away. I actually just redid my entire ground network to a single point on the jack plate and it quieted things up considerably. I should have done that originally, but never thought it would be an issue. I should have known better, having just built a tube amp recently. It's just good practice to always do that.
Cool, glad you got it sorted. :)
Quote from: pruttelherrie on March 08, 2011, 04:39:20 PM
Finished my Tiny Giant this weekend, it is indeed plenty loud. (Pics to follow later this week)
At first I thought I had some kind of overdrive going on when going past 9:00 on the (25k) volumepot, but that's only the case when I plug the guitar direct into the amp: going over 9:00 will not output more volume, only more distortion. But with a pedal in front I get waaaay more volume, although I still can't get over 9:00 with the volumepot. Haven't measured the levels yet, as far as I can see the TDA clips at that point?
pruttelherrie, can you give me some info on your guitar? What sort of pickups, etc.? I was testing the amp a bit today, and with a passive bass I was able to get it up to about halfway on the volume dial with absolutely no clipping, and this was quite loud.
When you turn it up to the point that it clips, is it ear-splittingly loud? Are you playing in some kind of practice space or just in your home? It could be fine, and you're just hitting the max volume, however if you're getting clipping at anything less than ear-splitting levels I wonder if there's an issue with your build, as in thedefog's ground situation.
I intend on putting this amp in a cab with a 8 ohm 12" celestion speaker, will this hook straight up.
Also how would I wirer up a superfly amp so that I can switch between the two in the one cab, would it be as easy as just using a 3pdt toggle with a couple of leds to show which is in use.
On a side note can the superfly circuit take 15V?
Thanks in advance
Quote from: Taylor on March 10, 2011, 01:26:42 AM
Quote from: pruttelherrie on March 08, 2011, 04:39:20 PM
Finished my Tiny Giant this weekend, it is indeed plenty loud. (Pics to follow later this week)
At first I thought I had some kind of overdrive going on when going past 9:00 on the (25k) volumepot, but that's only the case when I plug the guitar direct into the amp: going over 9:00 will not output more volume, only more distortion. But with a pedal in front I get waaaay more volume, although I still can't get over 9:00 with the volumepot. Haven't measured the levels yet, as far as I can see the TDA clips at that point?
pruttelherrie, can you give me some info on your guitar? What sort of pickups, etc.? I was testing the amp a bit today, and with a passive bass I was able to get it up to about halfway on the volume dial with absolutely no clipping, and this was quite loud.
I tested with an Ibanez VBT-700, the short-lived Flying V model from early 2007 introduced together with the Xiphos but discontinued shortly after. It has DiMarzio D-Activators. When I plug it in clean, it clips at home levels. When I use a random distortion box in front, it gets ear-splittingly loud. Well, I didn't dare to test it at full volume at home. I will test it in the rehearsal room on sunday and report back. I suspect it's just the difference between clean and distorted, at clean signal you need much more headroom/voltage to get the same perceived volume.
QuoteWhen you turn it up to the point that it clips, is it ear-splittingly loud? Are you playing in some kind of practice space or just in your home? It could be fine, and you're just hitting the max volume, however if you're getting clipping at anything less than ear-splitting levels I wonder if there's an issue with your build, as in thedefog's ground situation.
Ok, I spent half an hour with the signal generator and the scope, and this is what I measured:
* Input voltage (HP laptop PSU): 19.3V
* LM338 output voltage: 11.55V (disregarding the error from the cheapo voltcraft multimeter)
Next I put the volumepot at max, so no divider between TL072 and TDA. Then I turned up the sine-generator until clipping occurred at the output terminal. Voltages were as follows:
* Output: approx. 20V peak-peak
* Input TL072: 60mV peak-peak
* Output TL072: 200mV peak-peak
Does this make sense?
Iwan
If I wanted to add an eq like the Tonemender or Mr EQ to this, where would I put it? Right before the 1 microfarad cap before the volume?
Since those are both active EQs, it doesn't really matter. I would just put it in front of the whole circuit, and treat it like you have an EQ pedal in front of your amp.
If the TGA had a clipping section, you'd want your EQ after it, but since it's a clean amp, EQ can go in front. I have been meaning to test out a mod that turns the preamp buffer into a TS-style clipper, just haven't gotten around to it yet.
> * Output: approx. 20V peak-peak
> * Input TL072: 60mV peak-peak
> * Output TL072: 200mV peak-peak
> Does this make sense?
Yes.
The TL072 is wired for gain a bit over 3; 200:60, check.
IIRC the power amp has gain of 50 per side, so 100 both-sides; 20V/200mV, check.
60mV p-p is 20mV RMS (if you can ignore meter error, I can use 2 * sq.rt.2 = "3"). 20mV is THE classic input sensitivity for ~~~1960 Fender guitar amps. (50mV early 1950s, 1mV for some modern iron-shredders.)
20mV is an extreme setting; many players in many situations will turn-down on axe or amp. 200mV seems to be a hot guitar-cord signal. 200mV RMS is 600mV p-p. Times preamp gain of 3 is 1.8V p-p, below the TL072's 9V p-p limit. Taylor has designed so it takes 3V p-p 1V RMS input to overload the TL072.... such levels are rare, will overload the classic 1960s Fender's input, and if you have hotter signals you are probably looking for overload.
> ""Raise the 1k to: 1.2k 1.5k - the output voltage becomes: 13.75v 16.88v - the power becomes: 20w 24w""
The difference in "power" is, as Taylor says, moot.
> double wattage is not twice as loud, only 3db louder
At conversational levels, double power is not quite "one and a half times as loud". Above 80dB SPL (the only way to play guitar, even home alone) the 3dB increase is compensated by 1dB-2dB of inner-ear tense-up, so not even 1.4 times as loud. Barely audible. So whether it is 18W or 24W is pretty insignificant.
I do suspect that advanced users should trim the "12V" as high as it will go without exceeding 18V or getting voltage-drop on LOUD passages with low-Z speaker. Not so much for the "more Watts", but because this slightly reduces dissipation in the regulator and maybe total heat in the box.
Quote from: PRR on March 12, 2011, 11:19:33 PM
> * Output: approx. 20V peak-peak
> * Input TL072: 60mV peak-peak
> * Output TL072: 200mV peak-peak
> Does this make sense?
Yes.
The TL072 is wired for gain a bit over 3; 200:60, check.
IIRC the power amp has gain of 50 per side, so 100 both-sides; 20V/200mV, check.
60mV p-p is 20mV RMS (if you can ignore meter error, I can use 2 * sq.rt.2 = "3"). 20mV is THE classic input sensitivity for ~~~1960 Fender guitar amps. (50mV early 1950s, 1mV for some modern iron-shredders.)
20mV is an extreme setting; many players in many situations will turn-down on axe or amp. 200mV seems to be a hot guitar-cord signal. 200mV RMS is 600mV p-p. Times preamp gain of 3 is 1.8V p-p, below the TL072's 9V p-p limit. Taylor has designed so it takes 3V p-p 1V RMS input to overload the TL072.... such levels are rare, will overload the classic 1960s Fender's input, and if you have hotter signals you are probably looking for overload.
Ok, thanks for this explanation.
But now for the TDA: this one will overload way before the TL072 does. I have a feeling that the gain of the TL072 could to be turned down a bit, or I'll have to add a resistor to the volume pot to get more usable range. Or even make the preamp gain variable. A 'clip' led at the input of the TDA might be a handy feature in this case.
Quote> ""Raise the 1k to: 1.2k 1.5k - the output voltage becomes: 13.75v 16.88v - the power becomes: 20w 24w""
I do suspect that advanced users should trim the "12V" as high as it will go without exceeding 18V or getting voltage-drop on LOUD passages with low-Z speaker. Not so much for the "more Watts", but because this slightly reduces dissipation in the regulator and maybe total heat in the box.
Yeah I was thinking that. In a simplistic way: All the current delivered to the speaker has to go through the regulator. So the less voltage drop, the less power it has to dissipate.
QuoteAbove 80dB SPL (the only way to play guitar, even home alone)
Heheh this made my day :)
Ok, took it to the rehearsalspace this afternoon.
It is LOUD, but you'll have to manage your levels right to get the max out of it and the volumepot has no volume effect past 9:30.
Playing through a 4x12 (V30's), at 16ohm it was not loud enough for our typical rehearsals, but in the 4ohm input it was ok. It was pretty bright/trebly though, it might need some kind of low-pass.
Please note: I'm not complaining here, just reporting!
Taylor, thanks again for providing this kit!
Iwan
Cool, glad you like it.
When you say it sounds pretty bright/trebly, what you're hearing is the actual sound of a guitar without tone-shaping. :icon_wink: I actually like it the way it is (I also play it through a 15" bass cabinet, so that will give me much more low end than a guitar 4x12), but I always assumed that most people would not want to play it straight without any EQ or pedals in front. If you want a more common guitar amp sound, you definitely need to get that with your pedals or by adding some kind of EQ to the amp.
> LOUD
> the volumepot has no volume effect past 9:30.
> pretty bright/trebly
Odd. The gain is very typical of other guitar amps. The amp is "flat", and guitar amps usually boost treble.
Makes me wonder if there is some build error. Wrong-value cap in wrong place.
Is volume pot linear or audio?
If no build error: if you have space, you could insert the classic Fender Tone Stack. Re-scaled for the lower impedance of TDA. Cuts gain, and allows taking out the nasal midrange so boom and sparkle cut through.
(http://i.imgur.com/DCqsj.gif)
Uh-oh some misunderstanding here.
Rehearsalspace testing was with a rackmount high-gain tube preamp. (Full disclosure: Ultimately I'm only interested in tah br00talz, even though I'm a FX junkie with a case of GAS)
I had to turn down a lot of trebles to get it to sound like the normal rackmount (tube) poweramp.
This build used the musicpcb kit, I don't think I have mixed up capacitors.
Quote from: pruttelherrie on March 14, 2011, 08:32:23 AM
Uh-oh some misunderstanding here.
Rehearsalspace testing was with a rackmount high-gain tube preamp. (Full disclosure: Ultimately I'm only interested in tah br00talz, even though I'm a FX junkie with a case of GAS)
I had to turn down a lot of trebles to get it to sound like the normal rackmount (tube) poweramp.
This build used the musicpcb kit, I don't think I have mixed up capacitors.
I just built a Big Muff tone stack into it right on a pot and that worked pretty well for being able to dial in a nice warm sound. Then again, I'm also using a cheap-o single 12" speaker, so it was already a little dark sounding. But I like that so it works great for me as a practice/synth/effects testing amp for home.
Hey guys,
I finally had time to test this guy out tonight. So far all I've done is populate the board and gator clip the peripherals so I could try it out (with heat sinks in place).
Sounds great, but there's a lot of hum---is this likely simply because it's not boxed up or have I over-simplified the grounding scheme by not connecting anything together (just all leads from the PCB as shown in the PDF)? How particular does the wiring need to be to avoid hum as well?
What I can hear sounds great though, so I'm very excited.
Thanks!
Check back over the thread, especially thedefog's posts, who had the same problem. Not having it boxed is probably at least part of the problem.
I was messing around with it tonight using an OD/Boost circuit in front as a preamp and ooh boy that was fun.
So far I find my Tiny Giant (un-boxed, just gator clipped) to get unruly very quickly with a turn of the volume knob (though I'm using a linear 10K, as that's all I have right now, so my taper isn't what is expected). The best result so far has been with the amp very low, but a MyTon Blonde in front supplying the gain.
I could use a bit more treble so far, but the cab I'm running it through is far less than ideal. Very fun.
Er, Taylor ... Got my TG board populated ... but I seem to have an extra cap (224L) , from the kit ... did I miss something ??? I can't seem to find a place for it ??? Can't wait to get the TG working/playing !!! :icon_biggrin:
No, that's just a freebie. ;) There was an error with some of the kits that they got a wrong cap, so I went back and added the correct cap to them, but left the wrong one in. So that extra 220n is not needed.
OK, Thanks !!! I looked and looked for that one ....hahahahahaha :icon_lol:
I am using a 6 inch 4 ohm speaker rated at 65 watts. It has a pretty good size magnet. Is this a suitable speaker for maximum volume. It sounds really good but wondering if a lesser speaker would be better. I was going to post a pic of the finished cabinet but couldn't figure out how to do that.
There's no issue with underpowering a speaker. If you want more volume, you'd need to check out the speaker's sensitivity/efficiency rating, and you also need to take into account the efficiency of the cabinet it's in. Guitar cabs are basically the worst cabinet design possible from the standpoint of real engineering, and in general they have very bad sensitivity ratings. But most guitarists prefer that type of cabinet for the sound.
> a 6 inch 4 ohm speaker rated at 65 watts
A small speaker with a large power rating, mass-market, is surely a LOW efficiency speaker.
(There's also hot PA system array midranges, but flubby home speakers are a million times more common.)
Fondle the paper. Is it thin and hard (and light) like typing paper? Or thick and fluffy (and heavy) like compressed paper towels?
To get LOUD you want a large speaker or a large amp (or both). "Large" amps are not physically large and no longer very expensive. When customers demand compact boxes and medium loudness, the designer goes with a small speaker and "large" amp to brute-force the insufficient cone area.
Also small speakers "sound" small. Your ear can tell the size of a sonic object; sometimes small speakers doing full-orchestra can trick the ear and "sound big", but a naked solo guitar makes the source size more obvious.
If you are broke, but happy, do it.
If you can spear a few dozen bux, get a GUITAR speaker nearer 10". Aside from being light and efficient, it has "zing" that you don't want in a hi-fi but DO want when making music with the fairly boring sound of bare steel string on solid axe.
If you want a MAXimum of sound for a minimum of Watts (as in tubes or battery-power), go with the biggest cone(s) you can carry. A Four-Ten stack is an excellent start. But a tight fit in the Civic.
I have a concept that guitar "should be" a Ten or a Twelve, about the size of the active part of an acoustic guitar's soundboard. (The edges don't vibrate much.) And electric guitarists want "MORE!" and should start with the killer Two-Twelve Twin. (OTOH there's kick-butt sound in one heavy-duty Twelve with a 300-Watt amp.)
> the efficiency of the cabinet
Cabinets don't have an efficiency.
Speakers and their cabinets/baffles "should" be integral, but are normally made by very different workshops, and speaker makers don't like to get involved in cabinets (which are often more looks than function).
Cone speakers "need" a baffle to support their lowest octaves. The box has little effect in the speaker's middle register, but a naked speaker is gut-less. A large baffle supports down to a certain bass limit, a clever tuned box can support even better to a certain note then sacrifice all lower notes.
> Guitar cabs are basically the worst cabinet design possible from the standpoint of real engineering
No, they are (many of them) an excellent compromise between efficiency, projection, and size, over the narrow band and desired response shape for guitar. This is a different problem than what T&S published on. Thiele's work is applicable, but too high-level for ordinary people, and focuses on the "flat" result. Small specifically targets extended lows in small boxes, rather than the rising response and LARGE cone area needed for loud portable guitar amplification. Don't let the experts buffalo you. The Fender Twin is a fine design for ballroom use. The Twin with two JBL D-120s is an astonishingly efficient air-whacker, 100Hz-1KHz. It sucks below 80Hz and the phasiness above 500Hz is very strong. An unfaithful hi-fi but a wonderful guitar voice.
Ok, me debating you is like me picking a fight with Ivan Drago, but what the heck? ;D
Quote from: PRR on March 31, 2011, 01:10:21 AM
Cabinets don't have an efficiency.
Perhaps you meant this as more of a semantic argument, but do you disagree that, for example, a horn loaded cabinet increases coupling efficiency? And does that not have the effect of blasting my ears more?
Quote
> Guitar cabs are basically the worst cabinet design possible from the standpoint of real engineering
No, they are (many of them) an excellent compromise between efficiency, projection, and size, over the narrow band and desired response shape for guitar. This is a different problem than what T&S published on. Thiele's work is applicable, but too high-level for ordinary people, and focuses on the "flat" result. Small specifically targets extended lows in small boxes, rather than the rising response and LARGE cone area needed for loud portable guitar amplification. Don't let the experts buffalo you. The Fender Twin is a fine design for ballroom use. The Twin with two JBL D-120s is an astonishingly efficient air-whacker, 100Hz-1KHz. It sucks below 80Hz and the phasiness above 500Hz is very strong. An unfaithful hi-fi but a wonderful guitar voice.
Well... for example, standard guitar cabs have intense beaming and terrible off-axis frequency response. That could be improved easily and with no drawbacks. The freq response you mention might be right for the guys 15° off-axis, but for anybody right in front of the cab all they hear is 1k shredding their ears, and for anybody 50° off, all they hear is mud. If you like the response of that cab, wouldn't it be nice for the whole audience to hear it?
Maybe my assessment was exaggerated, but unlike tubes, I don't see much reason to cling to obsolete tech in this particular instance. But it was mostly meant as an aside, and I don't begrudge people using what they like.
Ok, now go ahead and break me (http://www.youtube.com/watch?v=ygQvB6OjHOU). :)
SO, it definitely needs to supply more than 4A? I have an extra laptop supply that can do 3.4A.
QuoteSO, it definitely needs to supply more than 4A? I have an extra laptop supply that can do 3.4A.
Mine draws about 1A when I first turn it on for a second or two. Then it settles down to about 70ma with no input. With the volume turned up and playing hard it doesn't draw that much. Even if the laptop supply can't supply more than 3.4A (and it probably can for intermittent peaks), I would think it would be fine.
I believe Taylor's recommendation is a conservative one, based on the theoretical power requirements of the chipamp.
I'm finally ready to box mine up. For the sake of simplicity I'm going to ditch the OD-pedal-as-preamp and just implement the BMP tone control. Where do you think the best place to slot that in would be (I assume I could interrupt the connection to the volume pot and toss it in there...)?
I would do it the way PRR has suggested here:
http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg768743#msg768743
Quote from: Taylor on April 04, 2011, 03:05:59 PM
I would do it the way PRR has suggested here:
http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg768743#msg768743
Ahh, didn't see that. Nice looking option. I don't think I have room for so many knobs in my enclosure though. A simple single knob tone-control is all I can likely fit.
> more than 4A? I have an extra laptop supply that can do 3.4A.
http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg764759#msg764759
We are veering off-topic.
I stick to my suggestion: if Tiny Giant is to play LOUD with reasonable total-rig size, use a large (8"-12") light-cone speaker in some form of baffle/box. In today's speaker market, suitable speakers are almost all "guitar speakers" (a few PA speakers work, at higher price and less flavor).
> Perhaps you meant this as more of a semantic argument
Well, I mean that driverless cabinet efficiency is dead zero.
> for example, a horn loaded cabinet increases coupling efficiency?
OK, granted, quite true.
How many horn-loaded GUITAR amps are there?
"Coupling efficiency" is the crux. There are no good speakers. The compromise chosen for home hi-fi, TVs, car-audio speakers is smooth modest output with cheap chips to brute-force bad coupling.
Horns have their own problems. They must be big. They beam. They will not cover a large frequency range with high efficiency and useful beamwidth, so must be 2-way or 3-way, which is not a Good Thing even when necessary. Splitting the band seems to be more obvious on a single widerange instrument than on a complex full-band signal. Most practical horns have further problems.
Horns are efficient and also LARGE for their bass limit. Does it make sense to use your 20W Tiny Giant amp with a 15% efficient 150 pound 3-foot horn? No more than it would to carry a 0.1% efficient shoebox speaker and a 3,000W amp. If anybody still needs 3 acoustic watts, 1.2%+300W to 5%+75W rigs work well.
The direct radiator has a goal efficiency which it will cover over a certain bandwidth, and a fairly constant sensitivity for a few octaves more. The cabinet affects only the lowest octave of that range.
> standard guitar cabs have intense beaming and terrible off-axis
So do non-electric instruments. Trumpet is wickedly beamy. Violin/viola (or acoustic guitar!) pattern is like a mutant sunflower. Woodwinds radiate dipole different every note. Piano is wack. Nobody has a problem with that. (Except the sax-players.)
OTOH, a mis-spent youth did too much work with pure synths and hi-fi speakers. Little of it worked as "music"; it was a job. By choice, I would rather be in a dive with a Twin.
> That could be improved easily and with no drawbacks.
In music, "flawless" is boring. Writers write about "improved" and some products are available: BOSE's 'stick' stage-speakers are technically fascinating, but have not caught-on. Nobody redesigns guitars or pianos for "constant directivity". (Price and traditions are objects, but even so....)
Finally boxed mine up tonight! I added a pilot light, on-off toggle and BMP tone knob. Sounds great so far! I'm just waiting to decide what to draw on the top of the box, then I'll post pics!
Got mine finally assembled , did my continuity checks and fired it up .... Now not really being a fan of SS amps , I must confess this one sounds pretty darn GOOD !!! :icon_biggrin: The Clean Tone is very Musical , and even the distorted Tone sounds pretty smooth !!! And it does get LOUD !!!! No hum I can tell ... and I have a very usable full range on the V pot (much like any other SS amp) ... Very COOL little amp , easy project .... I'd recommend this one to everybody !!!! :icon_mrgreen:
I'm using the IBM 16V 4.5A PS... with the mute switch ... Perfect !!!!
The only problem I'm having is keeping the tiny enclosure in one place, so I put some some Velcro on the bottom to secure it to the pedalboard... Problem solved !!! :icon_biggrin:
Thanks for the build report! Never thought this little guy would please tube amp fans with its tone, so that's very nice to hear.
I use mine every day for both guitar and bass and still really like it. I keep thinking about adding some EQ and clipping and all that, but honestly I like it a lot without any of that.
Taylor BIG THANKS !!!! I Love this little amp .... :icon_mrgreen: Perfect just like it is !!!! :icon_wink: (http://www.wattkins.com/files/wattkins/rave_0.gif)
(http://www.wattkins.com/files/wattkins/TG%20guts%20.jpg)
(http://www.wattkins.com/files/wattkins/TG%20Fin.jpg)
I'm loving this little guy! Throuth a 12" speaker it really wails. So Happy I might have to get another one (for my bandmate to use with her keys).
Here are a couple pics of my Tiny Happy Giant---I added a pilot light, BMP tone control and on/off switch (disconnects power):
(http://dogisblue.com/images/pedals/tiny_giant_amp_01.jpg)
(http://dogisblue.com/images/pedals/tiny_giant_amp_03.jpg)
(http://dogisblue.com/images/pedals/tiny_giant_amp_02.jpg)
Finally got to test my TG amp after sorting through a load of post divorce "pack it & run" boxes. It was the last thing I built before getting ousted. :D
Using an old Altec 418B (15" 8 ohm) in a "nothing special" homemade open back pine cab it sounds simply fantastic! Way more volume than my new neighbors can tolerate. :icon_twisted: Nice & clean too.
Time to build another and go stereo.
Thanks Taylor!!! 8)
Awesome build Paul! The color and graphic are perfect. Does the BMP tone control work well with the amp?
Thanks for the report, Dave, glad you're liking it. I, too, was surprised the first time I fired it up at the volume and clean tone. I've never gotten it loud enough to distort like Star Geezers - need to get some practice space so I can hear what it sounds like clipping. I figured it would be horrible, since we usually hear that clipping a SS amp is to be avoided. But maybe not?
Quote from: Taylor on April 09, 2011, 03:02:33 PM
I figured it would be horrible, since we usually hear that clipping a SS amp is to be avoided. But maybe not?
Only one way to find out, eh? :icon_lol:
Quote from: Taylor on April 09, 2011, 03:02:33 PM
Awesome build Paul! The color and graphic are perfect. Does the BMP tone control work well with the amp?
Thanks for the report, Dave, glad you're liking it. I, too, was surprised the first time I fired it up at the volume and clean tone. I've never gotten it loud enough to distort like Star Geezers - need to get some practice space so I can hear what it sounds like clipping. I figured it would be horrible, since we usually hear that clipping a SS amp is to be avoided. But maybe not?
Thanks Taylor! I'm going to be recommending this circuit to anyone I come across...very happy with it!
I find the BMP tone control to be very effective. I had to use an audio taper pot, as that's all I had, but it still dials in (or out) a great deal of treble.
I was playing my Tiny Giant through a 12" in a homemade cabinet (used to be a reel-to-reel suitcase) with a Jay Turser mini-Les Paul and it sounded amazing!
I too expected the usual SS distortion , but was most pleasantly surprised ... So Happy , I went all out and decorated it ... (http://www.wattkins.com/files/wattkins/TG%20%20Deco.jpg)
And even made a short clip ... http://www.wattkins.com/node/17710
I made one for both bass and synth use (2 inputs) in a 1590B, and added a power off switch via a pot with a switch built in. Here's what it came out looking like:
(http://spaceryerson.com/pics/tga1.jpg)
(http://spaceryerson.com/pics/tga2.jpg)
(http://spaceryerson.com/pics/tga3.jpg)
We tried it out last night at rehearsal through a 1x15" bass cab, which isn't ideal for synths. It sounds pretty good! My wife (who's using the amp) uses a bass eq pedal for tone shaping, which helped dial out some of the inherent problems with the cab. The only problem I ran into is when both the synth and the bass are plugged in at the same time, there is an immediate volume drop for both. Would adding buffers to both inputs cure this?
Quote from: space_ryerson on April 13, 2011, 01:06:29 AMWould adding buffers to both inputs cure this?
Yes, but you might also just try adding putting a resistor in series with each input:
bass in - 10k resistor - "node a"
synth in - 10k resistor - "noda a"
"node a" goes to TG input
Quote from: Taylor on April 13, 2011, 02:09:00 AM
Quote from: space_ryerson on April 13, 2011, 01:06:29 AMWould adding buffers to both inputs cure this?
Yes, but you might also just try adding putting a resistor in series with each input:
bass in - 10k resistor - "node a"
synth in - 10k resistor - "noda a"
"node a" goes to TG input
Interesting, I'll give it a shot, and let you know how it goes. Easy enough to try the resistors before bothering putting the buffers in. Thanks!
It's a fun project, by the way!
Cool, glad you're liking it. :)
The resistors will do the mixing better than just connecting them directly to each other, however I suspect you'll have some volume issues, since synths are line level and passive basses are instrument level. You probably want an actual active mixer.
I suspect you're right as well. For what it's worth, it's an active bass, and the last pedal in the chain is a buffered bypass (DOD Bass EQ). I'll give the resistors a shot tonight and see how it goes, and take it from there.
Forgot to post this here when I finished it, I might add some sort of tone control to it but its nice and loud so far :icon_twisted:
(http://img831.imageshack.us/img831/864/dscn0010q.jpg)
Did a side by side with a .22 caliber and they both had about the same amount of clean headroom with the cab I was using.
I was wondering how long it would take for us to see a "Tiny Green Giant"! Awesome.
Quote from: ckyvick on April 14, 2011, 07:28:54 AM
Did a side by side with a .22 caliber and they both had about the same amount of clean headroom with the cab I was using.
Ooh... take that, EHX. :P
Bass direct from the axe? That's a rather different signal than the already-amplified output from a synth or other Line-level source.
Pre-amp the axe with the preamp Taylor gave you; sneak (mix) the synth in after the preamp and before the power amp.
plan (13KB GIF image): http://i.imgur.com/Uill1.gif
If the synth has Volume control, the added pot may be omitted (you still need two 10K or 15K resistors). The mix network breaks-into the return from original pot wiper.
Thanks PRR! I'll give it a shot.
edit: I gave it a try without the second 10k pot. Although the synth has a volume control, the amount of noise that gets amplified makes me think I'll need to add the second pot. Even with the synth off, just having the second cable plugged in adds a degree of noise. It's too late to drill tonight, so this will have to wait until tomorrow.
I just built my Tiny Giant Amp. I'm going to use it with my DIY two channel amp with "Dr. Boogey" & "English Channel" as a preamps. In the build pdf it says that "you can take the regualted voltagefrom here...", so does it mean I can use that to give power to each preamps? Do they all have to be in the same ground? Thanks!
I built one of these as a test amp for my electronics workbench. I liked it enough, I ordered three more PCB's, and am going to make test amps for some of our repair guys at the shop, so they can stop having to go over to our shop amp, which is frequently busy with someone else's job.
I'm also thinking of making a couple for use as the stereo "wet" amps in my dry/wet guitar rig (one or two "tone" amps that are always dry, and then taps from their output transformers get sent to all the time based effects - chorus, delay, etc. - which get returned to the "wet" amps.
Gabriel
I've been running the TG as a "second" amp ... My guitar has a piezo bridge (Mike Christian) and i'm running that > the TG , the magnetics into a homemade tube amp ... Really get some interesting Tones by using both at the same time ... very FULL ... For the rhythm bits I just turn down the tube amp (guitar V pot) .. And if you spread the speakers apart , it really increases the Hugeness of the sound... (http://www.wattkins.com/files/wattkins/rave_0.gif)
Quote from: ckyvick on April 14, 2011, 07:28:54 AM
Forgot to post this here when I finished it, I might add some sort of tone control to it but its nice and loud so far :icon_twisted:
(http://img831.imageshack.us/img831/864/dscn0010q.jpg)
Did a side by side with a .22 caliber and they both had about the same amount of clean headroom with the cab I was using.
Wouldn't that make this the "Little Green Sprout"... :icon_mrgreen:
Quote from: Psychemic on April 15, 2011, 06:36:51 AM
I just built my Tiny Giant Amp. I'm going to use it with my DIY two channel amp with "Dr. Boogey" & "English Channel" as a preamps. In the build pdf it says that "you can take the regualted voltagefrom here...", so does it mean I can use that to give power to each preamps? Do they all have to be in the same ground? Thanks!
In general, all the grounds in any effects/amp system will connect. You can connect your grounds from your preamps to the TG board, or to the guitar input jack ground, which would probably be easier.
Yes, that point can be used to send power to your preamps. Note that the voltage is more than 9v - it will be 11.6v if you use standard values on the TG PCB.
Quote from: Taylor on April 15, 2011, 01:42:11 PM
In general, all the grounds in any effects/amp system will connect. You can connect your grounds from your preamps to the TG board, or to the guitar input jack ground, which would probably be easier.
Yes, that point can be used to send power to your preamps. Note that the voltage is more than 9v - it will be 11.6v if you use standard values on the TG PCB.
Hey thanks for the reply. What I read at least Dr. Boogey can handle 18 volts so 11.6v shouldn't be a problem.
Hey Taylor, I sent you an email but haven't heard from you yet.
If I wanted to go with a bit more traditional power supply, using a transformer and such, is there a resource you recommend, or even an idea of what kind of transformer I should be looking for? I have very little experience with that kind of power...
Jacob
Hey Jacob, sorry I hadn't answered your email yet.
I actually don't know much about power transformers - part of the reason I wanted to design this is to have an amp that didn't need a PT, for size, cost, and safety reasons. You might actually want to go with a different amp PCB if you're going to use a PT - you're going to need to add the diode bridge and big caps for the power supply, so you might as well go for a PCB with all that integrated on the board, rather than having to add a second board for the power supply.
D'oh, just checked and I see you've ordered the TG kit and received it already. :icon_redface:
If the only reason you want to do that is to have an IEC inlet on your amp, my personal solution was this:
Use a hole saw to cut a ~1" hole in your box, mount the laptop supply inside the box/cab with its AC inlet inside the 1" hole. You now can plug in the laptop supply's AC cable, and remove it for easy transport, etc.
You can still do a linear power supply with the TG, but I can't give too much guidance on that I'm afraid. You might want to bypass the voltage regulator, but I'd check out some solid state power amp schematics to see what's normally done.
I didn't even think about that Taylor! Brilliant.
Got any eBay links for a good powersupply?
jacob
> Although the synth has a volume control, the amount of noise
Raise the mix-resistor on the line/synth side to 33K, 100K, or more.
Ideal goal is for synth hiss-floor to come out the speaker similar to room noise-floor (different in the midnight lab or the happy-hour saloon, some judgement required), and for synth maximum output to come out at or slightly above the Giant's full ~~20 Watt limit.
It may not be possible to meet both goals in a quiet space. But in a paying-gig situation, when the max-output gain is right, the hiss is often a non-issue (below crowd noise).
This also improves gain in the preamped path, by shifting the mix from 50:50 to something like 80% preamp 20% line.
> If I wanted to go with a bit more traditional power supply, using a transformer
Living in the past.
Assuming full 20W output, the raw DC should be around 11, 12, 14V with at least 2 Amperes. OTOH at idle current goes near-zero yet voltage must not rise much over (IIRC) 18V.
That's a very tight spec for a small transformer. Only 28% different, and small PTs have 20%-25% regulation, plus 5% or more uncertainty in wall-voltage, plus you can't get the eXacT voltage rating you want without custom-costs.
18V-14V 2A DC means a "10V or 12V 3A" transformer, a 10A FWB, and about 10,000uFd of 20V cap. And a line-fuse! Depending where you shop, that's $20-$40 of heavy metal.
Plus the extra-care needed to wire wall-voltage without shock or fire. You can do it; it is much better if some other person checks your work (we are most blind to our own oversights).
OTOH apparently excess flatop supplies sell REALLY cheap. The wall-voltage safety issues have been DEALT-with, in design, testing, certification, and by the fact that they made thousands of them before yours (not a "one-off"). And the supply is regulated just a little above the voltage we need, so that a not-excessive $2 regulator can nail the supply voltage for-sure.
And yeah, if you don't like cord-bricks, tuck it inside. These bricks do need cooling, but for the typical flaptop brick and this amp they don't really need to be out in the open.
Having built many Tube guitar amps , with big power transformers and the like , when I saw the TG , and the power supply choices , I was totally impressed with the Beautiful Simplicity of this amp ... :icon_wink: I must confess , just building this for the Fun of it ,but turns out I was totally surprised how well it worked and how really GOOD it sounded ... :icon_cool: :icon_cool: :icon_cool:
Great having the PS and it's heat and noise far away from the amp... aside from the PS "affordability" ...(read: Cheap) I think Taylor did a Super job figuring all this out . and after having played on it , I wouldn't change a thing ... :icon_mrgreen:
Ps. I did try it out at band rehearsal , and through my 2-10" Celestion Rolas (total 4 R) , it Was LOUD enough to keep up with the band ... Very Impressive !!! ... :icon_biggrin:
Looking forward to building another one soon ... :icon_wink:
Quote from: jkokura on April 15, 2011, 11:53:21 PM
I didn't even think about that Taylor! Brilliant.
Got any eBay links for a good powersupply?
jacob
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=290429762390#ht_2793wt_1139 (http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=290429762390#ht_2793wt_1139)
Here's the one I ordered. Voltage wasn't too high, puts out 4A, and it's only $12 shipped to Canada
I'll follow-up when I receive it, hopefully it comes with a power cord!
As for mounting it into the enclosure, could it make the amp really noisy? Might not be a problem for me, as I'm using a D or C-sized enclosure, but in a BB it would be cramped in next to the board ???
EDIT #2:
Anyone know where I can get a 6.0mm x 4.4mm DC jack? The local place doesn't have it and none of the DIY stores carry it either... Would be nice to be able to use one PSU for many amps instead of lugging plastic boxes and cords, and having to figure out which one goes to which amp... :-\
So, finally some pics of my build. I find 'Tiny Giant' not as awe-instilling as for example 'Tiny Terror' (already taken, I know) so I went with 'Tiny Trepidation' to still have a sense of unease.
(http://dl.dropbox.com/u/17081629/tinygiant/IMG_0321.jpg)
(http://dl.dropbox.com/u/17081629/tinygiant/IMG_0327.jpg)
(http://dl.dropbox.com/u/17081629/tinygiant/IMG_0329.jpg)
And although I renamed it, attribution where needed: (too bad it's going to be covered by velcro for pedalboardmounting!)
(http://dl.dropbox.com/u/17081629/tinygiant/IMG_0335.jpg)
The waterslide decals got attacked by the paint...
And finally a gutshot:
(http://dl.dropbox.com/u/17081629/tinygiant/IMG_0337.jpg)
The PCB is mounted 'upside down' so I could place the pot, switch and led where they are. Hell to mount it though, I had to glue the plastic washer and the nut to the chips before sliding the unit in place and screwing the chips to the side. The remaining space is going to be filled by either a preamp/compressor/whatever or by a 16V -> 9V power supply regulator to be connected to the second PSU plug so I can power the rest of the pedals from it.
Your photos aren't showing up for me...
Hmpf, dropbox weirdness. Fixed the links in the post, should be ok now.
Nice builds, guys!
I'm curious now, what would stop someone (say, me) from adding a 9v out jack to their build to power pedals, taking it from the pad on the board previously mentioned (supplying 11v or whatever it actually was)? Ground issues, I suppose?
Just one more little question .... mine has a little Hum , except when I touch the guitar strings .... I was wondering if it would be effective to run a ground wire jumper from the input jack ground lug , to the negative side of the DC jack ...???
Quote from: p_wats on April 20, 2011, 09:45:49 AM
I'm curious now, what would stop someone (say, me) from adding a 9v out jack to their build to power pedals, taking it from the pad on the board previously mentioned (supplying 11v or whatever it actually was)? Ground issues, I suppose?
That was exactly my plan with the remaining space in my build.
Quote from: StarGeezers on April 20, 2011, 11:58:18 AMmine has a little Hum , except when I touch the guitar strings .... I was wondering if it would be effective to run a ground wire jumper from the input jack ground lug , to the negative side of the DC jack ...???
It already is connected, if you used both pads (GND and Input) on the PCB for connecting the inputjack to.
OK, Thanks Prut !!! Now where is that Hum coming from ??? .... turned off ALL my appliances, lights, everything , even tried different guitars .... still Hums ... :icon_rolleyes:
Quote from: StarGeezers on April 20, 2011, 01:37:23 PM
OK, Thanks Prut !!! Now where is that Hum coming from ??? .... turned off ALL my appliances, lights, everything , even tried different guitars .... still Hums ... :icon_rolleyes:
As long as it's keeping the beat and in the right key, seems to me you saved having to buy a vocal harmonizer!
Sorry, had nothing useful to say but HAD to say something...... Now back to our regularly scheduled programming.
I had a strange hum a while back with a chipamp. The second I'd touch the strings it'd be silent. Not light or appliance related. I have absolutely NO IDEA what made it go away, as it magically disappeared one day.
The only clue I have, as to its origin, is that I would unplug and move this amp often (always in the same room, same plug socket, though). Also, of note is that it still hasn't been boxed. Can't make any sense of it, nor do I care now, but it'd be good to know what caused it for future builds.
Quote from: PRR on April 16, 2011, 01:31:55 AM
> Although the synth has a volume control, the amount of noise
Raise the mix-resistor on the line/synth side to 33K, 100K, or more.
Ideal goal is for synth hiss-floor to come out the speaker similar to room noise-floor (different in the midnight lab or the happy-hour saloon, some judgement required), and for synth maximum output to come out at or slightly above the Giant's full ~~20 Watt limit.
It may not be possible to meet both goals in a quiet space. But in a paying-gig situation, when the max-output gain is right, the hiss is often a non-issue (below crowd noise).
This also improves gain in the preamped path, by shifting the mix from 50:50 to something like 80% preamp 20% line.
Thanks Paul, your description clears things up nicely. As a test, I tried a 100K pot in series with the 10K resistor to get a sense of noise floor vs. max-output. With the pot set at 60K (70K total resistance), the noise floor had dropped considerably (I had to shut down my computer to hear it), but the synths I tested were definitely loud enough. The amp still clipped with the synth volume going past 2/3rd's. I could probably increase the resistance a little more to make the maximum volume not as clipped. I'll likely use an 82k resistor.
Quote from: StarGeezers on April 20, 2011, 01:37:23 PMNow where is that Hum coming from ??? .... turned off ALL my appliances, lights, everything , even tried different guitars .... still Hums ... :icon_rolleyes:
Well, normally* ground is grounded to earth through the amp you're using (IEC receptacle). The Tiny Giant uses a laptop PSU which most probably isn't grounded/earthed. So if you use just the Tiny Giant, speaker, guitar, it won't be earthed until you touch the strings, ground of the plug, case (if grounded), etc.
As far as I know, earthed shouldn't be necessary but it won't hurt. Can somebody else with more knowledge chime in here?
* normally = 'standard' amp
Quote from: pruttelherrie on April 20, 2011, 06:17:31 PM
Well, normally* ground is grounded to earth through the amp you're using (IEC receptacle). The Tiny Giant uses a laptop PSU which most probably isn't grounded/earthed. So if you use just the Tiny Giant, speaker, guitar, it won't be earthed until you touch the strings, ground of the plug, case (if grounded), etc.
As far as I know, earthed shouldn't be necessary but it won't hurt. Can somebody else with more knowledge chime in here?
* normally = 'standard' amp
Makes sense and, if that is the case, just make sure to get a PSU with a grounded plug, they are out there. On the other hand, making sure the guitar is properly shielded and all connections are solid might help, too. It doesn't matter if there's no hum with other amps. You figure what the problem is when and where it occurs.
Posted more pics of mine, along with the homemade cab I'm using.
http://dogisblue.com/another-homemade-amp-tiny-happy-giant/ (http://dogisblue.com/another-homemade-amp-tiny-happy-giant/)
Still might drill in a 9v out jack for powering pedals though...
It should be no problem to add a regulated voltage output for your pedals - it was one of the things I suggested that people could do, actually. Keep in mind though that it will be closer to 12v than 9v, so make sure your pedals can handle that and will sound normal at that voltage.
You guys are spot on ... my IBM PS only has 2 wires ... no ground .... grrrrrrr!!!! Back to Flea Bay ... :icon_rolleyes:
Had to do some searching for a 3 wire AC adapter... found this one ... http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250694483500#ht_3489wt_922 Ordered it .... hopefully that will solve the Hum ... I Like this amp too much to be bothered by any little hum problems ... :icon_mrgreen:
FWIW, I'm using a IBM PS (2 prong), and I don't have any hum to speak of.
I am pumped! Looked in my garage and found my old Laptop PSU - 16vdc, 4 amps. I'm gonna build it, gotta go check parts!
Taylor , consulted one of my Mentors about the TG Hum ... here was his reply ... Just FYI... QUOTE: " Just to ask do you have the input jack set up to short the input with no cable plugged in? If so do you get hum when you turn the volume up with no cable? The other question would be does the hum go away with the volume turned down. What I am thinking is maybe the hum is power supply noise in the box that gets canceled out by out of phase noise going into the box. That would explain why the humbuckers or running two single coil pickups would have higher noise, less noise going in. The op amp is set up with a resistor divider across the power supply so any noise from the supply will be coupled into the input of the op amp. But now that I think of it with the input shorted the 100nF cap will be tied to ground and filter any noise from the supply, so to see if it is supply noise the input will need to be open. If it is noise getting through the LM338 a 10uf from the adjust pin to ground will improve the ripple rejection of the regulator.
A couple of quick ideas the 10uf connected to the 100k on the feedback of the op amp could be lowered to 22nf to 47nf to reduce 60Hz gain. Also if you change the 1Meg ohm resistor at the op amp + terminal to ground to 2.2 Meg ohm and connect the capacitor hooked to the 100k on the feedback of the op amp to the ground of the input jack you will have differential rejection of noise common on the inputs of the op amp. This will reduce the op amp gain to +2 instead of +3."
Taylor you have any comments about that ?? Thought I'd consult you before making any changes ... :icon_eek:
He's right about the 10uf cap connected to the 100k. That will be about 3db down at around 60hz. I wouldn't do this personally, since I am a bass player, but for guitar, your lowest fundamental is 82hz so it's a good idea.
I'm not a power supply whiz, but it seems unlikely to me that 60hz hum would be coming from the power supply, since the supply is a SMPS. Hum is obviously an issue with linear supplies, but I thought, but could be wrong, that in a switching supply, the power is going to be heavily filtered and chopped to the point that the mains frequency is completely gone. Hopefully one of the more learned gurus will chime in.
Did you ever try a 3-prong supply? I am using a grounded supply and I have never had any hum, even with the first perf board prototypes that weren't in metal enclosures.
I've tried mine (3-prong) supply all over lately and I get/don't get hum depending on where I am (crappy electrical in my apartment=hum with just about any audio equipment...).
Extremely Good news !!! The 3 prong PS arrived last evening ..so this morning , plugged it in and NO HUM !!! It was the IBM 2 prong PS all along .... Grrrrrrr!!!!!!
Guys, I really appreciate all the help with this matter!!!!!!!! ... All Good now , and the TG sounds Great !!! :icon_mrgreen: :icon_cool:
Big THANKS !!!! :icon_wink:
:) Glad it all got sorted.
Me too ... :icon_mrgreen:
Taylor , if you're able , please join us here http://www.wattkins.com/node/17514 for more TG discussion ...
Guys , got my TG all checked out , sounds Great , and it's getting double duty , not only as my Studio/practice amp , but I'm also throwing it in the gig bag as a "spare" amp ... a back up for the gig tonight , just in case ... I Love that idea !!! :icon_cool: :icon_cool: :icon_cool:
Now I just need to make another one so I can leave it there... :icon_mrgreen: Er, Taylor , you got any kits left ???
I just finished mine last week, and I have to say that the TG is awesome. I copied Taylor's layout in the 1590a with a standby switch and volume, and it fit great. I'm using it as a bass amp, and I can't believe how good and loud it is. I actually used it through a 4x12 bass cab with a drummer-only rehearsal, and it kept up as long as he wasn't hitting too hard. The cab was only 8 ohms as well! Can't wait to try it through an 4 ohm cab. I ordered an IBM 16v 4.5 amp power supply from ebay, and it's quiet as well. Awesome job Taylor!!! Pics:
(http://i56.tinypic.com/donedd.jpg)
(http://i52.tinypic.com/1z1uycz.jpg)
Nice! Clean build.
Has anyone managed to put their TG into thermal shutdown?
Taylor , I played mine for several hours at a time ... the case never even got warm , as I could tell ... :icon_cool:
I'll be ordering another kit if you have any left ...
Quote from: Taylor on April 21, 2011, 02:58:10 PM
It should be no problem to add a regulated voltage output for your pedals - it was one of the things I suggested that people could do, actually. Keep in mind though that it will be closer to 12v than 9v, so make sure your pedals can handle that and will sound normal at that voltage.
Or just add another regulator.
Quote from: Taylor on May 02, 2011, 01:17:07 AMHas anyone managed to put their TG into thermal shutdown?
A week ago I played stereo in one cabinet at rehearsal with the TG and an EHX 44 magnum. Stereo but not really: the 4x12 in stereo mode still had the (-) of the halves connected which resulted in a shutting of/turning on/shutting of pattern. Within 20 seconds (it took a short while before I realised what was going on) the TG got too warm to touch. It didn't break though, I let it cool down a bit before powering on on a mono cabinet and it worked as before. One tough f*cker it is!
Got my second TG kit ... that was FAST !!! Thanks Taylor !!! :icon_mrgreen: This amp works so well, makes me want to try some of Taylor's other offerings... :icon_cool:
Quote from: StarGeezers on May 05, 2011, 07:17:06 AM
Got my second TG kit ... that was FAST !!! Thanks Taylor !!! :icon_mrgreen: This amp works so well, makes me want to try some of Taylor's other offerings... :icon_cool:
Do it! I've built the Octave and Gristleizer and they are awesome!
PW, will do that ...Thanks !!!!
I built the tiny giant and it works fine except the volume pot doesn't work. Any help?
Sorry to be obvious, but if it really works fine, except that the volume knob doesn't work, then there's probably a problem in your volume pot wiring. Perhaps the lugs are shorted against each other, perhaps your ground connection on lug 1 is not connecting, maybe your pot is bad.
Hey Taylor,
How does the TG take pedals--or more accurately, how does it respond to higher input signals?
The reason I ask is that I've built a couple of SS amps (Ruby, Noisy Cricket) and while they sound great, they start to fart out when presented with any kind of boost or overdrive gain that isn't turned down.
I'm assuming that since this has a buffered and presumably better preamp, (in addition to taking a line-level keyboard signal) it would be fine.
I would like to build a TG as a backup amp for gig emergencies (like the EHX "bullet"-named amps).
Your boards/projects look great by the way--I hope to build an Echo Base and Clean Octave soon also. I've seen quite a few Echo Base projects out there.
Thanks!
J
Hey J,
The TG is fine with big signals and shouldn't clip in the preamp unless you hit it with a pretty massive boost. That said, slamming it with a booster won't necessarily sound good in the way that slamming a tube amp with a booster will. So it will take hot signals just fine, and it's meant specifically to go after effects. But I also wouldn't recommend hitting it with a clean boost if you're hoping for tube-like overdrive out of the preamp.
Quote from: myramyd on May 22, 2011, 07:59:55 PM
Hey Taylor,
How does the TG take pedals--or more accurately, how does it respond to higher input signals?
The reason I ask is that I've built a couple of SS amps (Ruby, Noisy Cricket) and while they sound great, they start to fart out when presented with any kind of boost or overdrive gain that isn't turned down.
I'm assuming that since this has a buffered and presumably better preamp, (in addition to taking a line-level keyboard signal) it would be fine.
I would like to build a TG as a backup amp for gig emergencies (like the EHX "bullet"-named amps).
Your boards/projects look great by the way--I hope to build an Echo Base and Clean Octave soon also. I've seen quite a few Echo Base projects out there.
Thanks!
J
I just got back from using mine on tour in eastern Canada and it sounded great. Took my OD and Fuzz pedals just fine...of course, like Taylor just said, it doesn't respond like a tube amp, but it played very nicely with my pedal board.
Cool,
Yeah, the reason I ask is more so there is some headroom available for various drive pedals and also for a simple boost for leads. I don't expect to drive it like a tube amp, so no problem there.
I've just noticed that quite a few SS amp designs (cheaper commercial combo amps and such) don't like it when you hit it with a clean/lead boost after the drive pedals--I'm talking like a +5-10dB boost, not a full-on slam.
I didn't think there would be any issues but wanted to double check.
I shall be ordering one very soon. I might combine with a bypass-able ROG Tonemender in the same box. If I go that route I will post pix!
J
Been playing my TG through an Eminence Wizard , and is it LOUD !!! Easily keeps up with the band ... :icon_cool:
I use my RFD OD pedal into it , no problems at all and very sweet and smooth sounding ... My first TG now lives in the gig bag as a "spare" amp .... The new one I'm building is just for the Studio ... :icon_cool: :icon_mrgreen: :icon_wink:
I think is messed up, i crossed the red V+ and black ground Ground at the dc input..
Is there some sort of protection in the circuit, or did the LM338 T blow?
any help is welcome.
When you say you crossed them, did they short out together, or did you connect power where ground should go and vise versa?
i connected power where ground should go and vise versa does this mean i have to teplace the lm 338?
Did you try swapping them to be correct and turning the amp on to see if it works? If it doesn't work, then yes switching out the regulator is probably the next thing to do.
Hi Taylor, i flipped the power and ground, i get a sound but it is a really distorted sound.
here's pinout for the tl 072
pin 1 3,3
pin 2 3,0
pin 3 3,0
pin 4 0,0
pin 5 8,8
pin 6 4,4
pin 7 3,0
pin 8 3,0
regulated output is 8,7 volt
it looks like i'll place an order for the LM 338
Hmm...after a few weeks of touring and actually using my Tiny Giant as my main amp at a couple small shows I've found something a bit concerning: everytime I use this amp while singing into a PA I get shocked. Not a huge spark or anything, but definitely noticeable with sweaty lips.
I assume this has something to do with a ground problem somewhere in my build. Anything jump out at you that would cause this?
I used a plastic jack for the speaker out, but a regular jack for the guitar input.
I just tested and I do get intermittent continuity between my LM388T and the enclosure---could that be it?
Hmm.
You're sure it's only with this amp and not others in the same club? This happens a lot with all kinds of amps, when the amp is on a different power system from the PA. The grounds of each system will sit at different voltage potentials relative to each other, and when you touch your strings which are connected to the ground of the amp, then sing near the mic, the voltage between these 2 grounds goes through you. My friend actually was telling me earlier today that he experiences this at his new practice space, using his amp which is some old Crate tube amp.
So, I can't say without knowing more if this has anything to do with the TG at all. But, having the heat sink of the LM338t connected to ground is definitely a bad thing which you should fix in any case.
I initially dismissed it as bad electrical at a club, but then it happened a 2 more clubs after that and in our jam space.
Tonight I managed to recreate the shock, then switch the Tiny Giant for a different amp (Roland Jazz Chorus) and the shock was gone.
As for the LM388T, I've installed the bushings/spacer, but still get intermittent continuity to the enclosure. Would there be obvious symptoms if this was connected to ground?
I also checked continuity between my plastic speaker jack and it too has continuity to the enclosure somehow. Are the grounds of the board connected to the ground running to the input sleeve?
No part of the speaker jack should be connected to ground. This is a bridged amp, so neither lead to the speaker is connected to ground. I can't really think of how it could be unless you tied all your grounds together - are the lugs of the speaker jack connecting to anything else besides the two SKR pads on the board?
Quote from: Taylor on June 08, 2011, 10:35:35 PM
No part of the speaker jack should be connected to ground. This is a bridged amp, so neither lead to the speaker is connected to ground. I can't really think of how it could be unless you tied all your grounds together - are the lugs of the speaker jack connecting to anything else besides the two SKR pads on the board?
I have nothing going to the lugs of the speaker jack other than the connections to the corresponding PCB spots.
I removed the board/jacks from the enclosure and tested for continuity on the board itself and I get continuity between one of the speaker connection points and the board ground.
Would these connections (speaker to ground, LM388T to ground) impede the amp from working, as it works absolutely fine until I sing in front of a mic (which is why I never noticed until now)?
I'm pretty confused about the regulator. The tab is connected to Vout. In other words, if there really is continuity between the tab and ground, I would expect the amp chip and opamp to have no power and not work.
If one side of your speaker is being grounded, I imagine that means that the output of one of the amps inside the amp chip (it's technically two amps, the outputs of which are connected to either side of the speaker) is being shorted to ground. I'm not an expert on bridge amp fail states, but I imagine this means you'd only get half the power out of it, if no other problems.
Quote from: Taylor on June 08, 2011, 11:44:55 PM
I'm pretty confused about the regulator. The tab is connected to Vout. In other words, if there really is continuity between the tab and ground, I would expect the amp chip and opamp to have no power and not work.
If one side of your speaker is being grounded, I imagine that means that the output of one of the amps inside the amp chip (it's technically two amps, the outputs of which are connected to either side of the speaker) is being shorted to ground. I'm not an expert on bridge amp fail states, but I imagine this means you'd only get half the power out of it, if no other problems.
Yeah, this is strange.
So I desoldered the offending speaker connection, but the pad on the board is still showing continuity to the ground pad. I don't really know what else to try at this point.
I mean... it seems to work fine, save for the fact that I can't use it with a PA...
New discovery: even when not attached to the enclosure my LM388T connects to ground. That tells me there's something on the board connecting the two, right?
P wats , are you using the 3 wire grounded power supply .... Since going to that , I have NO problems ... :icon_wink:
Quote from: StarGeezers on June 09, 2011, 07:42:34 AM
P wats , are you using the 3 wire grounded power supply .... Since going to that , I have NO problems ... :icon_wink:
My power supply has three prongs, but it's from eBay, so who knows about it's quality. I could try another.
However, what worries me is the continuity between ground and the speaker, LM388T etc. I'm testing when it's not plugged in...if that matters.
Hmmm...
Continuity between the LM338 tab and ground? As Taylor said, it's hard to understand how it would work at all if that were true. The tab on the LM338 is internally connected to the 12V output. Dumb question... are you really sure you are checking the continuity of the LM338 with ground? (The TDA7240 tab IS connected to ground, and looks very similar to the LM338 from the top side)
-Walt
Quote from: waltk on June 09, 2011, 08:29:39 AM
Hmmm...
Continuity between the LM338 tab and ground? As Taylor said, it's hard to understand how it would work at all if that were true. The tab on the LM338 is internally connected to the 12V output. Dumb question... are you really sure you are checking the continuity of the LM338 with ground? (The TDA7240 tab IS connected to ground, and looks very similar to the LM338 from the top side)
-Walt
Oh I definitely made sure to check the right tab. BOTH tabs show continuity to ground. Is it possible that my DMM has a much higher sensitivity and the beeping is a false positive?
Paul,
QuoteOh I definitely made sure to check the right tab. BOTH tabs show continuity to ground. Is it possible that my DMM has a much higher sensitivity and the beeping is a false positive?
DMMs that have a continuity test (beep) function only require some small non-zero resistance to consider the circuit complete - 50 ohms on my Fluke DMM. That wouldn't make difference for you because the LM338 tab should measure off the scale (high) resistance to ground. The TDA7240 tab should measure zero resistance to ground.
So based on your description (both tabs being connected to ground), if you measure the resistance between the two tabs (on the LM338 and the TDA7240), you are getting zero resistance between them? If that's true, then I would expect your power supply to shut down (temporarily or permanently) as soon as you connect power to the board. If the amp is working when you connect power, then the only explanation I can think of is that your DMM is bad. What is the actual resistance measured between the tabs (disregarding the beeping)? Zero?
-Walt
Quote from: waltk on June 13, 2011, 10:47:21 AM
Paul,
QuoteOh I definitely made sure to check the right tab. BOTH tabs show continuity to ground. Is it possible that my DMM has a much higher sensitivity and the beeping is a false positive?
DMMs that have a continuity test (beep) function only require some small non-zero resistance to consider the circuit complete - 50 ohms on my Fluke DMM. That wouldn't make difference for you because the LM338 tab should measure off the scale (high) resistance to ground. The TDA7240 tab should measure zero resistance to ground.
So based on your description (both tabs being connected to ground), if you measure the resistance between the two tabs (on the LM338 and the TDA7240), you are getting zero resistance between them? If that's true, then I would expect your power supply to shut down (temporarily or permanently) as soon as you connect power to the board. If the amp is working when you connect power, then the only explanation I can think of is that your DMM is bad. What is the actual resistance measured between the tabs (disregarding the beeping)? Zero?
-Walt
Thanks for making me second guess my DMM. I don't think it's broken, but it would appear the threshold for continuity behaves funny.
For instance, the TDA7240 to ground beeps consistently and measures 0 resistance (it bounces around the .00-.06 range and back over and over) while the LM338 to ground beeps momentarily and then the resistance climps to infinity slowly to infinity. For some reason my DMM is slow on the uptake.
Also, the speaker connection to ground does the same thing--beeps briefly to indicate continuity, but then you can watch the resistance climb to .5K (that still seems low, though...doesn't it?).
I'm glad this seems to explain the mystery of continuity, but I'm still getting small shocks from the microphone when I use this amp with a PA, while others don't have the same effect.
Could it have something to do with my power supply? I have 19V 4A 3-pronged supply on which I soldered a new jack (to fit a regular DC pedal input). Should I try an insulated input jack?
I appreciate your help and patience with this build. I love this amp when it's not shocking me! Ha.
Paul , sounds like something is still not right !!! :icon_eek: Mine works SUPER , no shocks or any other problems ... I did however use both isolators , supplied by Taylor , on the LM ,and both on the bolt inside and out , not wanting to take any chances ... I get an Open reading on mine .. :icon_mrgreen:
Quote from: StarGeezers on June 14, 2011, 08:26:32 AM
Paul , sounds like something is still not right !!! :icon_eek: Mine works SUPER , no shocks or any other problems ... I did however use both isolators , supplied by Taylor , on the LM ,and both on the bolt inside and out , not wanting to take any chances ... I get an Open reading on mine .. :icon_mrgreen:
Do you use yours with a PA (ie, while singing into a mic)? As that's the only time it shocks me.
I think the reason you get shocked is because ground on the Tiny Giant isn't connected to earth at the wall socket, so it probably isn't at the same level as ground on the PA. So if you're touching ground on the TG via your guitar strings and touch ground on the pa, by touching the mic, you'll get a shock.
I did a test with mine by measuring the voltage between the sleeve of a guitar lead plugged into the TG and the sleeve of a guitar lead plugged into my Fender amp, where ground is connected to earth at the wall socket, and measured about 0.2 volts. I don't know if this is enough to give you a shock, I didn't try and find out.
I don't know if there's a solution to this or if it is even the problem, hopefully someone like Paul or R.G. will pop by.
> this amp while singing into a PA I get shocked
What Ian says. "ground on the Tiny Giant isn't connected to earth at the wall socket, so it probably isn't at the same level as ground on the PA."
It "floats".
This depends totally on the power supply wart you use. Computer power supplies don't ground the same as stage-amp supplies.
It is VERY possible there are two 0.05uFd caps from each side of the line to "system ground". On 120V line this gives 60V AC from amp chassis (and jacks and guitar strings) to ground.
The 0.05uFd value is a compromise between reducing (computer) RF EMI, and human safety. 0.05uFd at 60Hz is about 53K impedance. 60V across 53K is a bit over 1 milliAmp current into a short-to-ground, perhaps half that to ground through human skin.
0.5mA is a tingle, and quite shocking when un-expected, but is significantly below accepted safety thresholds (2mA to 50mA max leakage).
> measuring the voltage between the sleeve ... and ... my Fender amp... measured about 0.2 volts.
Then your power supply either has extremely low leakage OR is somehow properly grounded all the way from wall to TG amp DC jack. 0.2V stray voltage is not uncommon on a "good ground". It may be 0.2V in the _Fender_'s input filtering.
> don't know if this is enough to give you a shock
Not unless you peel your skin and stick it right into a nerve. Put a dry finger on a 9V battery: no shock. Wet finger: maybe slight shock. Wire-up a 1.5V battery so both ends can touch skin close together. Very few persons will feel 1.5V. 0.2V is "nothing".
Not sure what you can do.
The "correct" answer is to have solid wire from wall-outlet ground pin to amplifier chassis. But that means hacking the power cord and adding a connection to go around the power-lump to the TG chassis.
You could keep buying $13 supplies until you happen on one with incredibly low stray leakage.
There is the old trick I used to use before modern grounding. Take any unused connector on the floating chassis. Run a cable to any unused connector another chassis which IS solid grounded. I took AUX OUT on the leaky film mixer to AUX IN on my PA mixer, then kept my AUX IN firmly down. The cable drained the leakage of the film mixer's 0.1uFd(!) caps across 2-pin plug. Signal cables are NOT rated for bet-your-butt grounding. Any REAL ground-fault would burn a hifi/guitar cable and leave you ungrounded. But sometimes you do what you do.
________________________________________________________________
> continuity between ground and the speaker
"Continuity" testers are for trailer light checks. Where you either have a solid metal path, or you don't.
Poking at semiconductors, there are all sorts of low-voltage and reverse-polarity "sneak paths" plus capacitors which confuse "continuity" tests.
> Is it possible that my DMM has a much higher sensitivity and the beeping is a false positive?
It is a poor tool for this work.
> beeps briefly to indicate continuity, but then you can watch the resistance climb to .5K
The "brief beep" is some large capacitor being charged by the "continuity test" voltage. Poke some caps and see.
The "0.5K" is a false reading; it is probably a 0.6 Volt threshold of some transistor junction. (Try some other diodes and see if they all read "half-K".)
Wow! Thanks for all that info. Very helpful.
The option of hacking the power cord sounds like the most doable, but still an awkward bit of work. Otherwise I simply consider this a non-stage amp (which most people would anyway, but I play smaller venues with no drummer).
We just plug ours into the SAME power strip as the PA .... and use a foam mic cover... No shocks , no spit in the mic. If we loan the mic out, it gets a different cover... :icon_razz:
Is it possible to have a headphone out for the Tiny Giant?
Also, for the power jack, does it need to be isolated from the chassis? In other words, do I have to use a plastic jack like the ones commonly used in pedals?
20 watts would be ear-splitting for a headphone amp. You could turn it down, but I think you'd be in serious danger of destroying your hearing by having that kind of power available. I built the headphone amp at General Guitar gadgets, works well and could certainly be implemented together in the same enclosure with the TG.
The chassis is grounded. Most people these days use center-negative power plugs, due to the Boss standard. Since you're not powering the TG on a daisy chain, you can use whatever plug and jack you like, but if you're using a metal one, you would of course need to use a center-positive plug and jack so as to not short v+ to ground.
That's what I figured, Taylor. Thanks for the speedy response!
Quote from: Taylor on June 16, 2011, 02:47:27 PM
20 watts would be ear-splitting for a headphone amp. You could turn it down, but I think you'd be in serious danger of destroying your hearing by having that kind of power available. I built the headphone amp at General Guitar gadgets, works well and could certainly be implemented together in the same enclosure with the TG.
Oh, I don't know. I've recorded in a couple of studio's that were using 100 watt Crowns as headphone amps. You just need to be careful about how high you turn it up, but having the available head room sure does make things sound nice. Well, nice for headphones.
Gabriel
Quote from: StarGeezers on June 15, 2011, 05:49:00 PM
We just plug ours into the SAME power strip as the PA .... and use a foam mic cover... No shocks , no spit in the mic. If we loan the mic out, it gets a different cover... :icon_razz:
That's actually not a bad idea. I've been thinking about bringing my own mics to clubs anyway...
Thanks for all the help guys.
Hi there.... My kid and I are seriously considering building this amp and pairing it with a FET-based preamp project I found. I have an old amp that I'm planning to gut the electronics out of and using for this purpose. I read the PDF for the project stating the recommended power supply voltage range, but would it be safe to use a 24V/4A switcher? Unless I'm reading it wrong, the LM338 datasheet reads as if it's good to 30VDC. I'm sure I'd have to go with better heat-sinking if it works.
The main reason I'm looking at using this sort of power supply instead of a laptop supply is so I can mount it a little neater inside the cabinet. If I have to go with the laptop supply I'll make do but I'd thought I would throw the question out here.
You'll be throwing away half the power to heat, so you'll need really good heat sinking. Otherwise I don't foresee any issues. I would still personally prefer to go with a lower voltage supply - I think you can mount them cleanly, but that's me.
Thanks for the reply, Taylor. Since I'm not interested in building a solid-state space heater, I'll just go with the laptop supply and mount it nice. Perhaps if it turns out allright I'll post a photo of it. It turns out that we'll be using every available pot and switch hole on the existing control panel so it shouldn't look too bad.
So I plan to build this with my daughter. Some planned mods:
1- 2 input jacks so she can plug in a mic at the same time.
Full range speakers, again, the mic.
Building it in a small combo, but with a 1/4" out so it can be a head too.
Probably gonna be pink and purple...
Alrighty Team,
My tiny giant fired up and I am trying to use it with a charge pump (madbeans "road rage") to supply 18v. It works fine until I turn it about half way up I get severe oscillation and pulsing. Can this not be powered this way? Am I not supply enough current?
Thanks folks.
ps- All the pin voltages checked fine and I made sure the speaker output was isolated. Used the meter to check for grounding.
Scott
QuoteCan this not be powered this way?
Correct, it can't be powered this way. The onboard LM338 will just regulate the supply down to about 12V anyway.
QuoteAm I not supply enough current?
Correct, the the 1044/7660 in the RoadRage can't supply enough current.
alrighty. :(
thanks team!
I am planning to put this in a radio shack plastic enclosure. I noticed that the aluminum lid fits under the plastic one. Is this sufficient for use as the heat sink? What sort of temperatures are normal during use?
I would not recommend a heat sink with less mass than a 1590a enclosure. I'm not exactly sure to which lid you're referring so I don't know if it will work.
My 1590a box gets just slightly warm while playing for 40 minutes or so. This is at loud apartment levels with bass. If you were gigging with it you'd want more mass than a 1590a.
QuoteI am planning to put this in a radio shack plastic enclosure. I noticed that the aluminum lid fits under the plastic one. Is this sufficient for use as the heat sink? What sort of temperatures are normal during use?
The plastic Radio Shack boxes I've seen have a thin gauge aluminum cover. The problem is there is not much mass to absorb the heat, and not much surface area to radiate it - especially if the aluminum cover is hidden under the plastic cover. You could try a separate heat sink within the box, but even that would be a marginal solution because there is no to way to vent the heat, and it would build up inside.
How hot are these supposed to get anyway ???? I always run mine Clean/sweet spot , no real heat detectable .. but a friend who built one is using an OD in front, reports a WARM box ... :icon_eek:
How big is the box? I'd been a while since I've driven the crap outta mine, but I recall the 1590BB that it's in getting pretty warm where the chips are located. I imagine something like a 1590A would get pretty cooked if the amp were driven hard.
Mine is in the 1.5" X 2.5" X 4.75" box .... hardly gets warm ... You guys ever try heat sinks... they Work !! Fins look Cool too !!! :icon_cool:
I have mine just about finished. The Tiny Giant works great. The preamp I made works and sounds fine but for some reason the tone controls aren't working correctly just yet so I have to sort that out.
If anyone's interested in adding a headphone output to theirs, I borrowed the headphone jack from my old Squier amp and it has the resistors mounted right on it. From the schematic, it looks like it's just 220 ohm 1 watt resisitors going into both of the stereo contacts of the headphone jack. The schematic shows the headphone jack and speaker hooked to ground so of course that's a no-no. I just routed the wire that's grounded on the Fender amp to the other side of the Tiny Giant's output.
Here's the entire Fender shematic showing the heaphone jack output:
http://music-electronics-forum.com/attachments/3932d1230346488-squier15.gif (http://music-electronics-forum.com/attachments/3932d1230346488-squier15.gif)
Quote from: waltk on July 06, 2011, 12:07:44 AM
QuoteI am planning to put this in a radio shack plastic enclosure. I noticed that the aluminum lid fits under the plastic one. Is this sufficient for use as the heat sink? What sort of temperatures are normal during use?
The plastic Radio Shack boxes I've seen have a thin gauge aluminum cover. The problem is there is not much mass to absorb the heat, and not much surface area to radiate it - especially if the aluminum cover is hidden under the plastic cover. You could try a separate heat sink within the box, but even that would be a marginal solution because there is no to way to vent the heat, and it would build up inside.
Walt, I understand what you are saying, and I agree. By the time I had read your response, I had already finished assembly as planned (aluminum cover under plastic, with a hole cut out of the aluminum for the controls to go through). I put this into the 2.5X3X6" project box.
I tested it at full volume on a 4 ohm speaker with my Les Paul for one full hour. I am slightly surprised that it leveled off at 104 degrees Fahrenheit. Less than 10 minutes after I shut it down, it was back to around room temperature (75 degrees)
I do not know the temperature limits of the components. I do have room to add a fan to cool the amp, but do I really need it?
I am also not averse to scrapping the entire Radioshack box idea for a better one, but it does seem that it may work.
QuoteI do not know the temperature limits of the components. I do have room to add a fan to cool the amp, but do I really need it?
I am also not averse to scrapping the entire Radioshack box idea for a better one, but it does seem that it may work.
The datasheet for the chip says it can handle a junction temperature of -40 to 150 degrees C. It seems you are easily within that range. Were you measuring the temperature of the chip, or the air in the box? Also, the chip has a built-in thermal shutdown. So if you like that particular enclosure, and you didn't encounter the thermal shutdown with an hour of hard playing, go with it. It sounds like you have plenty of thermal headroom and wouldn't need a fan.
Quote from: waltk on July 11, 2011, 12:00:57 AM
Were you measuring the temperature of the chip, or the air in the box?
I was measuring the aluminum plate behind the chip, not the air. I held the box shut with masking tape while playing. Then about every 10 minutes would grab my infrared thermometer, take the plastic cover off, and aim just behind the two chips. It leveled off at 104 after 30 minutes, and stayed there for another 30.
Anyone tried running this amp kit off a 12 volt battery?
Yep. Works great. If you want to do this, you should bypass the onboard LM338 voltage regulator. You can just leave out the LM338, the two (120R and 1k) resistors, and the associated 100nF cap. Hook up your 12V input to the middle pad for the LM338. If you want to also run it off of a higher-voltage power supply, you can leave the parts in place and hook up an external switching arrangement. Caveat: we're talking about a large 12v battery - right? It needs to supply enough current.
Quote from: waltk on July 21, 2011, 11:00:19 AM
Yep. Works great. If you want to do this, you should bypass the onboard LM338 voltage regulator. You can just leave out the LM338, the two (120R and 1k) resistors, and the associated 100nF cap. Hook up your 12V input to the middle pad for the LM338. If you want to also run it off of a higher-voltage power supply, you can leave the parts in place and hook up an external switching arrangement. Caveat: we're talking about a large 12v battery - right? It needs to supply enough current.
yup, I was looking at compact deep cycle batteries?
do you have any battery suggestions?
Quotedo you have any battery suggestions?
Nope. Any car battery would run it for a long time. I'm not sure how big a compact deep cycle is, but if you wanted to go lighter-weight, you can also power it with a rechargable (lithium?) tool battery.
Hey Taylor,
I put together my TG yesterday. Hooked it up this morning and the LM338 (literally) exploded immediately.
Here is some more info:
Before I connected the offboard wiring, I checked the heat sinks and speaker jack lugs for continuity with ground (the enclosure). None of them showed continuity. I did not recheck after I connected the wires to the jacks (I know). But when I check them now, both heat sinks, both speaker wires, and all 3 pot wires show continuity with ground. I disconnected the speaker jack and heat sinks from the enclosure and they still show continuity with ground. So the continuity is somewhere on the board. With a visual inspection I don't see any problems that are immediately detectable. There may be a cold joint somewhere but it's hard to see any off hand.
The PS is 15V 6A if that helps.
Two questions:
1- Will I just need to replace the LM338 or would you guess more components are also fried?
2- Any thoughts where I should check on the board for problems? i.e. how everything seems to be connected to ground? Any particular spots I should check first?
Sorry for the incoherence. My brain is going nutty trying to figure this out. :icon_eek:
Thanks in advance.
J
Hmm. Can you post a photo of the build? Maybe that will have some clues.
If the regulator blew, perhaps it took the amp chip down as well, in such a way that the amp chip shorted its outputs to ground. I think it's got to be something along those lines unless you just have a solder bridge somewhere.
Okay, here we go: (note that the screw is only there to hold it in place for taking photos)
(http://www.mccallumdesign.com/photos/bad_tg1.jpg)
(http://www.mccallumdesign.com/photos/bad_tg2.jpg)
(http://www.mccallumdesign.com/photos/bad_tg3.jpg)
And you've got some kind of velcro or foam under the PCB to keep the bottom from shorting out against the enclosure, right?
Yeah, I had some cardboard underneath it and was going to replace that with foam tape. I just plugged it in so I could get a voltage reading on the TL072 and it exploded immediately.
The continuity checks where I noticed the heat sinks and speakers connected to ground were with it detached from the enclosure (as it is now--but without the screw).
J
It's weird because I can imagine ways in which the speaker jacks could short to ground, but the fact that all of those things including all three pot wires are connected to ground is completely strange and I honestly can't think of how that could happen, other than a short on the board or conductive flux.
I would go through and reflow all of those joints. Most look fine, a couple look iffy. Since you have to replace it anyway, I'd pull the regulator out of the board, may fix something if it's internally shorted in death. If you haven't desoldered from a double sided board before, go slowly and make sure that the solder is liquid all the way through and on both sides before pulling.
Okay, I can do that.
I figure worse case if I can't figure it out I can just order another kit and start over! Hopefully I can salvage what's already been done though.
I was having trouble getting some of the joints to flow they way I wanted them to so it could be a problem there. If I manage to find something that works I will report back.
Thanks for your help,
J
First post!
bought the kit today, its going to get my second project.
can i just ask if this would be ok ?
http://www.ebay.com.au/itm/16V-4-5A-72W-F-AC-adapter-IBM-A-R-T-X-I-series-08K8204-/230569983399?pt=AU_Laptop_Accessories&hash=item35af0abda7#ht_4082wt_1139
Thanks guys! and Taylor it looks great!
Hello,
I just ordered two of these--hopefully these are the correct replacement?
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_192284_-1
Thanks,
J
Clarke: yes that will be fine.
myramyd: yes that's the right one.
After reading the last few posts in this thread, it brought to mind a little would-be problem I came across while building this amp. I had to drill holes in my heatsink to accept the screws for the chips. When I got it assembled, I did the continuity test and found that both ic's backs were shorted to the heatsink, and therefore ground.
I double checked the insulators and bushings and they were straight and looked good. I even tried nylon screws and nuts, still shorted. After scratching my head for a while I checked the heatsink and found just a little bit of burr left over from the drilling and it was poking through the insulators.
It doesn't look like this would be myramyd's problem, but I'm just throwing this out there.
Hello to all. Been lurking a while, but took the plunge.
So, I'm pretty much a noob. Done some modding and work on guitars, and built with moderate success the Noisy Cricket. Just ordered the TG and am going to put it into a gutted combo.
I'm interested in putting the BMP tone stack into it. My question is this: where does it go? Does it attach to the input jack and then into the circuit, or should it go before the vol pot, as described earlier? I searched a few places for the answer, but it seems to be obvious to most people. Just not me.
I'm excited to do more builds and keep learning. Reading schematics alone is still very challenging and tortuous for me. Pictures and layouts are my friends at this point. But it's coming along.
Thanks for any insight and tips.
Cheers!
This post has a 3-band tone stack:
http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg768743#msg768743
If you just wanted the one-knob BMP control, that's still a good spot for it.
Thanks. That's what I thought, and was referring to in my post, but just wanted to clarify. This will be going into a gutted Traynor TS-15. Will connect the speakers to a jack, so I can use the onboard TG, or connect other little amps to it. Stoked.
Hey Taylor,
I'm happy to report that I have the TG working now after installing a new chip and reflowing some joints.
I'm unhappy to report that I'm an idiot...
I didn't realize that I had the polarity reversed on the power jack. I wired the power supply plug to be center positive and didn't make the connection that it's the opposite of how pedal PS are wired.
Luckily I didn't blow the replacement chip--it just got fairly hot while I tested voltage and made the realization.
At least it's working now! Lesson learned... :icon_redface:
J
> polarity reversed on the power jack. ...it's the opposite of how pedal PS are wired.
Something for the manual.
Quote from: PRR on August 24, 2011, 01:46:28 AM
> polarity reversed on the power jack. ...it's the opposite of how pedal PS are wired.
Something for the manual.
Huh? The Tiny Giant can be wired however you want, but in general most people are wiring them the same as pedals - center negative. So there's nothing special about this circuit that requires you to wire things differently from the way you're used to.
Hi again,
I've decided to trash the preamp I had built for this, since I did a questionable job on it and it had some issues. The TG works great however.
I'm about to build another preamp using subminiature pentode tubes.
Would the input impedance of the TG play well with the high output impedance a tube preamp, or should I use a buffer on the output? I'm thinking it will be OK, since the first preamp I tried was a JFET design, without a buffer- and it was PLENTY loud. Just want to be sure.
I know this is a strange question, but is there anything that can be easily substituted for the isolation material? I managed to lose one of the two pieces and was hoping to replace it with something I can find locally, rather than making an online order for such a small part. Thanks for any help folks!
Quote from: neutronarmy on August 30, 2011, 03:02:38 PM
I know this is a strange question, but is there anything that can be easily substituted for the isolation material? I managed to lose one of the two pieces and was hoping to replace it with something I can find locally, rather than making an online order for such a small part. Thanks for any help folks!
Yeah, anything that is an electric insulator will work. Rubber, silicone, plastic, wood, paper, cardboard, but you need to be really serious about checking that there's no continuity with the enclosure this way, and of course fashioning something that's the right shape/size is tricky. I can also mail you some replacements for the price of shipping.
Quote from: haroldjenkins on August 27, 2011, 01:40:10 AM
Hi again,
I've decided to trash the preamp I had built for this, since I did a questionable job on it and it had some issues. The TG works great however.
I'm about to build another preamp using subminiature pentode tubes.
Would the input impedance of the TG play well with the high output impedance a tube preamp, or should I use a buffer on the output? I'm thinking it will be OK, since the first preamp I tried was a JFET design, without a buffer- and it was PLENTY loud. Just want to be sure.
The built-in preamp of the TG is basically just an opamp buffer, so I'd go from your tube preamp output to the regular input of the TG and it should work well.
Quote from: Taylor on August 30, 2011, 04:20:19 PM
The built-in preamp of the TG is basically just an opamp buffer, so I'd go from your tube preamp output to the regular input of the TG and it should work well.
I suppose I should have paid more attention to the schematic. There is TL072 with JFET inputs there cleverly disguised as an opamp. Thanks for the reply, Taylor.
Hi Taylor and you all
this is just to report I just became part of the Tiny Giant Amp family!!! worked at first go! Deadly silent and great sound even into a home stereo 2 ways speakercabinet, cannot imagine it into a proper guitar speaker!!!
just one question about the PSU, my one has 3 wires, 2 braids insulated from eachother. I get 19.5V and I use to power up the TG, then in the second bread there's another blu wire and I can get 12.5V with the 1st bread. Do you thinks I may use this "spare" wire to power up my pedalboard after a 9V regulator ckt, ot it will suck current from the TG?
thx m8!!
ciao
Armando
Quotejust one question about the PSU, my one has 3 wires, 2 braids insulated from eachother. I get 19.5V and I use to power up the TG, then in the second bread there's another blu wire and I can get 12.5V with the 1st bread. Do you thinks I may use this "spare" wire to power up my pedalboard after a 9V regulator ckt, ot it will suck current from the TG?
Well done on the TG build - it's always nice to have a build work on the first try.
To answer your question, it depends on how much current is available from the PS, and how much is required for the pedalboard. It's also possible that the 19.5V and 12.5V output are rated for different current output. In general, supplying a pedal would require a tiny fraction of the output available from the PS. Many pedals only draw a few ma, digital pedals might 90 or 100 ma. Unless you have a huge current requirement on the pedalboard, it should be fine.
Thx Walt
I've just looked again at the sticker on the back of the PSU, there's no mention of this double voltages, it just says, among other things , output 18.5V at 3.5A.
So I'd better leave my pedalboard powered up with its own PSU, to avoid problem and the search for 3 prongs jack and plug :D
Thanks again
Ciao
I've had a very difficult summer, but I finally got this one built! :o
It's great! Works well in the same box as a Dr. Boogie, just biased and it was ready to play. I want to do a volume test but I doubt the neighbors would be too happy at this hour!
Thanks for designing this and making kits available
Hey guys, I want to include a 9v power out to power my pedals with this amp and I was wondering if you can run a 9 volt regulator off of the 12 volt regulator in this build?
This has been a frequent subject of posts in this thread. Take a look back at some of the other posts.
Short answer: Sure (with a couple minor caveats).
Hi there
Almost finished!!
Put the PSU directly into the enclosure, then I had a "Condor Cab Simulator" board laying around so I put it inside to test, OMG!! perfect!!! it's powered up directly with the PSU, a DPDT with a Millenium bypass et voillà, selectable CabSim depending on the external cabined available!!
Then I just take the power from the PSU connected to a small perfboard with a LM7809 and a couple of caps, and got 9V on the back to power up my pedalboard! perfect too, no hum no noise....... (btw yesterday I left it on (unattended!!! :icon_mrgreen: :icon_mrgreen: ) for 3 hours, nothing hot, if I touch the bottom plate, where all the heatsinks are connected my hand is warmer than the plate.)
.................Taylor what have you done!!!
Still need something to be fixed, ie cut the PSU cables and put 4 fixed resistors instead of the pots on the cabsim, and redo the wiring even though I may leave as it is now.... it sound perfect!!!
(http://i256.photobucket.com/albums/hh174/arma61/100_1464.jpg)
(http://i256.photobucket.com/albums/hh174/arma61/100_1471.jpg)
Rear
(http://i256.photobucket.com/albums/hh174/arma61/100_1465.jpg)
Details!
(http://i256.photobucket.com/albums/hh174/arma61/100_1467.jpg)
(http://i256.photobucket.com/albums/hh174/arma61/100_1468.jpg)
Guts!
(http://i256.photobucket.com/albums/hh174/arma61/100_1469.jpg)
(http://i256.photobucket.com/albums/hh174/arma61/100_1470.jpg)
Ciao!
QuoteAlmost finished!!
That's beautiful. Nice work!
Yes, looking good Armando. :)
Thanks again to Walt for his many contributions to this project.
Quote from: waltk on September 19, 2011, 10:30:57 AM
This has been a frequent subject of posts in this thread. Take a look back at some of the other posts.
Short answer: Sure (with a couple minor caveats).
OK so I looked back and I can't find anything other than people talking about doing it. From my understanding as long as the on board regulator in the tiny giant amp has an output of higher than 11.5v (as according to the datasheet of my 9v regulator) I can attach this output straight to the input of my 9v regulator?
Now I can suspect it's not as easy as that. So does anyone know of any problems that might come about from this?
QuoteNow I can suspect it's not as easy as that. So does anyone know of any problems that might come about from this?
No problems. It's really as easy as that. As long as the power supply can supply all the current required, and the add-on 9V regulator can supply the current for the pedal(s) you want to power, it should be fine.
Quote from: waltk on September 20, 2011, 09:03:27 AM
QuoteNow I can suspect it's not as easy as that. So does anyone know of any problems that might come about from this?
No problems. It's really as easy as that. As long as the power supply can supply all the current required, and the add-on 9V regulator can supply the current for the pedal(s) you want to power, it should be fine.
Thanks. How could I test the power supply for this? Is there a ball park figure I should be leaning towards for a power supply? Also my 9v regulator max's at 1 amp so I think that should be enough as I wouldn't have many on at once. At most I would be using one digital pedal?
QuoteHow could I test the power supply for this? Is there a ball park figure I should be leaning towards for a power supply? Also my 9v regulator max's at 1 amp so I think that should be enough as I wouldn't have many on at once. At most I would be using one digital pedal?
If your 9V regulator can handle 1 amp (e.g. like an LM7809), and is in a TO220 package, then it probably wouldn't even break a sweat - even with a fairly loaded pedal board. With one digital pedal, and a handfull of analog pedals, you probably don't need more than 200ma for all the pedals together. I doubt that you would even need a heatsink for the add-on regulator.
Taylor was pretty conservative in specifying the power supply for the TG. If your laptop power supply handles 3.5+ amps (as marked on the label), there should be plenty for all. Seems like the TG draws about 1 amp when it starts up, then settles down to a couple hundred ma at moderate volume levels.
Quote from: waltk on September 20, 2011, 09:55:05 AM
QuoteHow could I test the power supply for this? Is there a ball park figure I should be leaning towards for a power supply? Also my 9v regulator max's at 1 amp so I think that should be enough as I wouldn't have many on at once. At most I would be using one digital pedal?
If your 9V regulator can handle 1 amp (e.g. like an LM7809), and is in a TO220 package, then it probably wouldn't even break a sweat - even with a fairly loaded pedal board. With one digital pedal, and a handfull of analog pedals, you probably don't need more than 200ma for all the pedals together. I doubt that you would even need a heatsink for the add-on regulator.
Taylor was pretty conservative in specifying the power supply for the TG. If your laptop power supply handles 3.5+ amps (as marked on the label), there should be plenty for all. Seems like the TG draws about 1 amp when it starts up, then settles down to a couple hundred ma at moderate volume levels.
Ah that's great news. Thank's for all your help. Just one more question, would it be safe enough to just attach regulator to regulator or should I put some caps either side of my 9v regulator?
QuoteJust one more question, would it be safe enough to just attach regulator to regulator or should I put some caps either side of my 9v regulator?
Is this a standard linear regulator? Does the datasheet call for them? Can't hurt to have them. The smallish cap on the output side is usually there to improve stability and transient response. The one on the input side is probably not necessary.
What I ended up doing is setting up a 7809 in parallel to the TG. Works like a charm
The heatsink tab on 78xx regulators is connected to ground, so I used a standoff to mount it to the enclosure. Not sure if this could affect overheating of the amp at all, but my reasoning was that the added heat loss won't be shared with the TG's regulator; putting the 7809 at a distant site will dump the full amount at a "colder" spot.
My 1590C takes care of the heat anyways, but it's good practice, I guess?
Is it bad that I used a 1u polarized electro on the output, though? I doubt it's doing much seeing how my preamp's already got a 220uF, V+ to ground
Does this look like a viable option for a power supply?
http://www.amazon.com/PA3048U-1ACA-PA3282U-1ACA-PA3282U-2ACA-pa3260u-1aca-Satellite/dp/B001MQ35EY/ref=sr_1_5?ie=UTF8&qid=1316622461&sr=8-5
I am working on mine. Any reason I can't just add heat sinks and not ground either of them? I am using a roomy enclosure.
Any easy way to add an indicator light or use a lit toggle?
You can use heat sinks that aren't connected to anything, and then you don't need the spacers/bushings.
For an indicator light, just use an extra pole of your switch to power an LED with a series current limiting resistor.
Sweet, mine is a 15a 15v supply. Any suggestions on what value resistor to use for drop down to the LED? I am going to build a floor monitor rig with pedalboard combo thing.
You calculate the resistor value with this formula: R = (VS - VL)/I
where
R is the the resistance in ohms
VS is the source voltage
VL is the voltage drop across the LED
I is the current in amps that you want to light the LED
So if your source voltage is 15, and it's an ordinary red LED with a voltage drop of about 2V, and you want it fairly bright (20 ma current):
(15-2)/.02 = 650 ohms
I usually go with a bigger resistance because I don't like the LEDs at full brightness. Other types (colors) of LEDs can have a different votage drop. Google for "LED resistor calculator", and you'll find a zillion sites using this simple LED resistor formula. Some have calculators for making whole networks of LEDs in serial and parallel.
Thank you.
'lo all...
Have been lurking on this for a while... but with a few years of guitar mods under my belt and a couple of JFET Boosters and Ruby amps built, I think I'm ready to give the TG a go(!)
Just a couple of questions, please:-
1. From exploring the web sites, I find the TDA7240A is an obsolete component (so it says at Mouser, for example). I also can't find anyone locally who carries them (Australia). Any suggestions on what can be done to substitute another component in the design? (although, for the initial build, I fully intend to buy a kit)
2. A couple of people have used a Big Muff Pedal (BMP) tone stack in the 'middle' of the design to give some tone control. Can I ask what values of components did you use in the BMP tone control when used in the TG? Did you actually work out the losses, etc and/or use something like the Duncan Tone Stack Calculator (see http://www.duncanamps.com/tsc/) to design the response or did you just 'cut'n'paste' the original BMP design verbatim?
Many thanks for any forthcoming info...
> the TDA7240A is an obsolete component
If you have a contract with Banjo World to deliver 100,000 units within 3 weeks, and don't have parts in hand, you do NOT want to rely on any "end of production" or "obsolete" parts.
If you are just building one or a few units, if you can find some stock, if they actually get delivered, who cares if it is "obsolete"?
Actually I cared. About 1980 I designed for LM377 which was readily available. So available that I abused the specifications (35V on a "27V" chip). In 1990 the chip quit, but I had an extra. About 1999 it quit again, and LM377 was replaced by 377 with more letters, and that new chip was already "lifetime buy". I bought two, the first was still working when I left in 2010, and the extra is sitting inside the chassis. So it should be good until 2020, forty years after design/build. And that was an exceptionally bad design (I was young, and broke, thus reckless); chips well-used (like Taylor's plan) probably last 30-100 years each (not 4 in 40 years).
QuoteTDA7240A is an obsolete component
If you are in the States look here:
http://www.packetradio.com/catalog/index.php?main_page=product_info&products_id=1003 (http://www.packetradio.com/catalog/index.php?main_page=product_info&products_id=1003)
If you are in Europe like me I suggest Futurlec, who have both required chips for the time being. Post to The EU from the above link was 25 dollars on four 1 dollar chips.
Good Luck
Edit: I see now you are in Oz, Futurlec it is then, they ship from Thailand. The chip has only just been obsoleted so there will be some stock around, but you better get buying if you want a production run out of it.
I'm having trouble with the TDA7240 and grounding. On the directions, you say to make sure that the heatsink tab on the chip is not connected to ground. But on the datasheet, it says that pin 4 is connected to the heatsink tab, and on my board the hole for pin 4 is connected to ground. Doesn't this mean that the heatsink tab is connected to ground anyway? Or does it mean that I have a solder bridge or short or something?
Edit: I'm an idiot :icon_rolleyes: Could anyone with a working amp post some voltages for the 338, Tl074 etc?
Thanks!
Hey Guys, the kit arrived and looks great, but I'm waiting for the PS as well. I'm asking, is there's a way to put an aux input to play with a CD or mp3 player?Thanks
Hi guys!!
I have ? for you all, I've built my TGA with a CondorCab Simulator (from ROG) inside (switchable), it sounds great. I've played a little bit with it and looks like it sounds great with my, newly built, EasyDrive, and hopefully is going to sound even better with the OneChipChorus... So here comes my question ..... say I want these last two effects to be build inside the TGA box and have an outside box with two switches and LEDs for the effects... you know just like some Fender Amp!
how would you connect and switch those inside the TGA box, may I just run a cable (say 3m, 9ft) and connect the 3PDTs in the external box like they were inside a "normal" fx..... hmm...... I don't think so..... cable lenght capacitance and whatelse!! or do I need a relais switching setup.
Thx for your help !
Ciao
Edit: I've some DPDT relais, are they going to work with the Millenium Bypass setup ?
It is with great sadness and disappointment that I report the death of my Tiny Giant, a faithful companion on my pedalboard for the past six months. The cause of death appears to be an intermittent short at the point where I had soldered a Boss connector to the laptop power supply I used. There was a spot I missed applying electrical tape to. The amp died at practice on Wednesday. As it supplied power to my pedalboard, it took my pedals too.
The pedals, thankfully, survived. The amp did not. :icon_cry:
Let this be a cautionary tale.
Sad :icon_frown:
I read carefully about the specs of construction, and some of the threads about the current capability, and I searched in the datasheet of the chip but I don't founded nothing about that. So why this specs?, it's something about trial error?, I have a power supply of 15v and 1,5 Amp, and I want to use a 8ohm speaker. Any advice?
This is my guitar amp. Preamp, Overdrive, Reverb is my design. Power by Taylor
(http://i736.photobucket.com/albums/xx7/volkstompbox/photo1-3-1.jpg)
(http://i736.photobucket.com/albums/xx7/volkstompbox/photo2-3-1.jpg)
> 15v and 1,5 Amp, and I want to use a 8ohm speaker.
Should be OK.
For this amp (bridged-amps generally):
Multiply speaker impedance by 1.5. 8*1.5 is 12 ohms.
Divide 12 ohms inTO the supply voltage. Actually the internal regulated voltage, but it is safer to take the nominal external voltage. 15V/12= 1.25 Amperes current draw at full output.
This is less than the rated 1.5V of your supply. It sure looks worth a try.
Quote from: wakeuptone on October 08, 2011, 09:53:58 PM
This is my guitar amp. Preamp, Overdrive, Reverb is my design. Power by Taylor
Wow! I want one. :) Fantastic work.
Well, Job is done, finally I used a 19v 6a PS, and seems work great (the sound is pretty amazing and very natural). Now the bad news. The thing is really humming. First of all I made a mistake mounting the caps and one of the 22uf I put inverted, so it was a nightmare to desolding (I used a pump) and I think I broke one of the pads outside. Somebody can give me the voltage (the cap is the one is closed to the pin 1 of the tda). I want to check this to be sure it's not broken and is the possible humming problem. So for your convenience I describe all the setup. 3 wire PS. Aluminium case, isolated jack for speaker, non isolated jack for the input. And the negative is grounded to the box in some point or another.
I´m getting 5,36v aprox in both of them. So I think they´re working
Problem solved. Like the most of people who had the same problem it was the 3 wire plug. And why this if I saw that I have a 3 wire one?. Because the third vire it was disconnected!!!! Didn't remember I made by myself long time ago because the cable came with another country plug, so I leaved the ground unplugged. Dumbass.
I want to go a little far and put a 7809 regulator to feed my pedalboard. But I don´t want to get the current from the pcb, instead, direct from the input, so doesn´t matter if the amp is turned on or off. My question is, it had to be isolated too to avoid ground? or can be directly attached to the box ?(disipation can be better I think). Can I expect some problems in that way? Thanks.
Mine isn't isolated, as the heatsink on 78XX regulators is tied to ground. It'll work fine bolted onto your enclosure, assuming all 7809 chips are made the same way
Doesn't that get pretty warm dropping 6 volts (assuming 15 volt supply)?
Nope.
I'm running a boogie, so the current draw is small. I don't know what it is exactly, but assuming 50mA, that's 1/4W?
Then again, I've also got everything mounted in a C-sized enclosure.
I'm guessing it's not a good idea to run a dozen pedals off your TG supply, though. Especially not digital ones!
Right, if it's not drawing much then that makes sense. I was under the impression that people were powering their pedal boards off the extra amps. Perhaps they use a different method to drop the voltage.
Well here is mine. How you can see I inserted a 7809 in a small pcb with two filter caps, direct to the main supply so I can have the pedalboard feed-ed independently if the amp is turned on or off. The main supply is 6A so I don't expect current problems. I trimmed the back case to be sure is not in conflict with the 12v regulator. I want to put a one knob tone control like Paul did. And the next, is time to paint the whole thing. Best regards guys and thanks Taylor for this great project.
(https://lh3.googleusercontent.com/-m89tZzMdS9c/Tpoka-TlaYI/AAAAAAAAABs/j4J0RQYun78/s912/tinyGiant.jpg)
Your power supply seems to be good for the job, as I doubt you'll need anything over 1A for your board. If, however, you've got the TG cranked and you're feeding a lot of high-current-drawing pedals, it will get hot. I don't know exactly how hot, maybe just too much to touch, maybe enough to burn the tolex on your cab. It might have been wiser to mount your regulator board farther away from the TG to dissipate the heat over a larger area.
In any case, everything should be fine, just keep the heat issue in mind!
Enjoy your new amp :)
Okay, I need to order two power supplies for two separate tiny giants.
I understand the specs I need but there are SO many on ebay and amazon.
15-20V DC with at least 4 amps
Any recommendations for finding a power supply? Anything from our usual DIY vendors?
Maybe a switchable power supply for 15 to 20volts? (I have heard these are usually cheap garbage though)
Thanks for the help.
Scott
I would search for 15vdc laptop supply, then filter buy it now, priced low to high, and grab the first one that's an adequate amp rating. You can probably get them for $10 each.
I would avoid switchable voltage ones. That won't do any good for this amp because of the regulator, and it might make for weird issues.
Thanks Taylor,
Awesome, speedy reply.
Would there be a problem in just leaving out the 10k pot and running the signal straight to the TDA7240A from the TL072 through a cap?
No, no problems other than that it will be quite loud if you don't have a volume control elsewhere.
The board already has a cap before and after the pot so you could just jumper the pot pads. Make sure you know which two to jumper though. You could also leave one of those caps out, but honestly it's easier to leave them in IMO.
Hello Taylor,
(The bad luck continues!) My TG suddenly stopped working the other day. It was working fine--I was testing my guitar wiring and it was on, then I unplugged it from power, then plugged it back in 10 minutes later and it "thumps" the speaker when I plug in the power but no sound.
All the voltages still check out (jack, IC, etc.). The only thing I notice is that now the sleeve lug on the speaker jack has continuity with ground. Tracing along the schematic, I get ground continuity all the way along the path of that wire--Pin 7 of the chip, both sides of the 2.2R resistor, and both sides of the 220n cap. Don't know if that is normal or not but, I didn't get ground signal on that lug before.
Any ideas? Thanks.
J
What kind of jack is it? Any chance the jack is connecting to ground?
It's a plastic "Marshall" type speaker jack. It was working fine for a few months then it did this all the sudden. All I did was unplug it, then plug it back in 10 minutes later.
J
Hmm. Are the heat sink tabs of the ICs still discontinuous to ground?
The heat sink of the LM338T is not showing connected to ground but the TD7240A heat sink is (it was before this happened also). I have the spacers installed on both.
J
Hmm. Nothing springs to mind - I guess I'd look physically around the board to see if there's anything shorting these parts to ground. But you've probably tried that.
Yeah, nothing really looks like it--although I haven't pulled it out to look on the bottom of the board yet.
The one question I have--does the circuit have any kind of polarity protection? If you recall, I'm the one who first wired up the power backwards and blew out the LM338 chip. I replaced that chip and fixed the polarity and it has been working fine since then. I'm just wondering if I could have damaged something else back at the beginning and it just finally went? That's the only other thing I can think of.
J
There's no polarity protection on the board. I would be surprised if damage like that would be sustained but take such a long time to have any impact. I'd suggest taking a look under the board - it's quite possible that a pointy solder joint could poke through whatever you're using to isolate the board from the box, or something similar.
QuoteThe heat sink of the LM338T is not showing connected to ground but the TD7240A heat sink is (it was before this happened also). I have the spacers installed on both.
The heatsink tab on the TDA7240 is internally connected to pin 4 (ground) , so you don't need to worry about that. Pins 5 and 7, however, should only go to your output jack - and neither should be grounded.
According to the datasheet...
"Reliable operation is guaranteed by a comprehensive
array of on-chip protection features. These include
protection against AC and DC output short
circuits (to ground and across the load), load dump
transients, and junction overtemperature. Additionally,
the TDA7240A protects the loudspeaker when
one output is short-circuited to ground."
So temporary shorts of this kind shouldn't cause any permanent damage.
The heatsink tab on the LM338 is internally connected to Vout, and should never be allowed to touch ground.
While you're poking around the board, you should probably verify that all the external connections are still intact (power in, speaker out, etc.).
Sorry myramyd and all you guys to interrupt this troubleshooting... but it's just arrived!
(http://i256.photobucket.com/albums/hh174/arma61/TGAOC1.jpg)
The board is designed to have "on board"
-a power reguator to get the 9V
-an overdrive, it's the Easy Drive
-the wellknown One Chip Chorus, layout blatantly copied from Earthscum's layout ;D
-a Cabinet simulator, it's the Condor Cab Sim from ROG, on my own layout heavily based on Gringo's
-a relais switching to switch only the OD and the Chorus, the CabSim has its own DPDT on the front Panel
The big pad u c on the left is there because at the beginning I wanted to include the TGA on the board, but I did't dare to!! Taylor kit is sooo good!!!, so I leave the pad (and the other small one, to save etchant!! ;D )
I'm just populating it right now!! hopefully everything will be ok.
Ciao
Armando
Looks great Armando.
Hi all, it's about time for a newbie question. :icon_confused:
In place of the SPST toggle, I want to use an illuminated pushbutton similar to http://www.velleman.eu/products/view/?id=376866
My questions:
1) For this one in particular, I would wire it as NO, correct?
2) How do I feed current to the LED? I'll be using the extra 11.x volt output to power a preamp - can I still take it from there?
3) What size of CLR would I use in any case, the same as for a stompbox?
Many thanks in advance!!
Your link won't work for me - it just sends me to the home page - and I couldn't find it searching. Could you post the item number?
> sends me to the home page
Actually to the Pick-A-Country page, right? And Velleman does not offer all products to all countries.
Try this:
http://www.velleman.eu/products/view/?country=nl&lang=en&id=376866
FLAT STAINLESS STEEL PUSH BUTTON SPST 1NO 1NC - ORANGE RING
(http://www.velleman.eu/images/products/12/small/r2000o.jpg)
Has an awful lot of pins:
(http://www.velleman.eu/images/products/12/r2000_t.jpg)
SPDT 1NO 1NC
colour: orange
power supply LED ring: 12VDC
type: (on)-off
connections:
NC (normal closed): 1-2
NO (normal open): 3-4
Sorry for posting that one - my question is simply how to hook up an on/off SPST with a built-in LED.
Here's a couple of simpler ones that would make me just as happy :-) If you have trouble with the link, I picked Spain & English language on the home page.
This product ID is R1945A:
http://www.velleman.eu/products/view/?id=339466 (http://www.velleman.eu/products/view/?id=339466)
This one is R1399B - same idea, I think:
http://www.velleman.eu/products/view/?id=385530 (http://www.velleman.eu/products/view/?id=385530)
Hm, maybe I see the answer ... In looking at what PRR posted, it LOOKS like all I have to do is feed the switch 12V, figure out which lugs are the NO ones, & all will be well. Can I just "split" the 11.3V output I will use to feed the preamp and send 11.3V to the pre & 11.3V to the LED switch, or does something have to be done to it first?
Hi Guys,
I received my Kit from MusicPCB some weeks ago and I'm now buying the rest of components to put an amp together. I have a doubt regarding the volume pot.... Do I need a log or linear one? Schematics says "A", but you know... this means different things in Europe than in US... I assume it's a log ("Audio") one, but I'm not sure...
REgards,
Mat
Ah yes, I forgot about the Europe/US taper thing. I'm in the US, so I'm using the US terms. A is log (audio), B is linear.
My mnemonic is "A for audio, Linear B". Linear B being the famous ancient Greek script, of course. :icon_wink:
Great, thanks for the clarification!
New member, new builder, new in general :) I did my best to chew through the full length of the thread, but i'll definitely still have tons of stoopid questions!
First of all, thanks to Taylor for making this project officially available. I received the envelope full of goodness yesterday. Parts of nice quality, sexy PCB. And I'll get a suitable laptop PSU on Monday - really looking forward to test this little monster. I foresee it putting my LM386-based Ruby amp to shame :D It took me approximately 30mins to assemble (including a bit of time 'identifying' the resistors, using my own homebuilt 'resistor colorcode calculator'). Second of all, I just love how all these old laptop PSUs are being 'recycled' in such a meaningful way. Seriously, call me a hippie or whatever :D It really warms my heart to experience environmental responsibility in the guitar DIY scene!
- In reply #218 haroldjenkins offers a nice solution to incorporate an output for headphone. But won't it sound harsh without some cab simulation? Has anyone tried this out one way or another?
- I dream of stuffing some kind of tube-based preamp into the box also. I have the PCB for a SLO clone, but also the 'Pepper Shredder' looks good (http://www.tube-town.net/diy/lov/lov02-peppershredder-eng.html). Coupling together such two circuits, should I be aware of stuff like impedance or any-other-kind-of-electrical-expression-that-i-don't-know-anything-about which might impact on the sound in an undesirable manner??!
Anyways, I promise to do my best :) And I'll post some pictures as my build (hopefully) carries on.
I got hold of this IBM PSU today
http://imagehost.vendio.com/a/35097889/aview/IBM_Adapter_12J1443.JPG
It says 16V 2.2A, so I hope it'll do the job nicely... I really itch to test this out, but since i have no heatsink attached to the PCB yet, i'm afraid to fry my Tiny Giant :S
- Would my newfound PSU be able to feed my TG properly? I read that it needs an amp rating swinging from 1A to 5A throughout the thread here :)
- Could i be so cheeky to turn on my TG and test it for sound, rapidly like 30secs or something without chance of frying the little baby?
Cheers,
Flemming
That supply should work.
Re heat sinks, I can't recommend that you do that since you might wreck it and then blame me. :icon_wink: I would just try to screw the chips to any piece of metal on which you can get your hands.
Taylor,
I already have a very clean 10VDC supply (40,000 uF worth of filtering), so could I just bypass the LM338T and use unregulated power without dire consequence :icon_question:
You can do that and I foresee no dire consequences, but you will get lower power output with only 10v.
> use unregulated power without dire consequence
Yes.
The power chips is made to run 12V-14V un-regulated in a nasty environment (car).
Respect the MAX Voltage of the power chip, but this is 18V steady and >24V blips, so a "10V" supply is unlikely to ever get close to danger.
This power chip is very good at rejecting crappy power. Alternators whine and kick-out, fuel injectors CL-TIK-ing constantly, some relay in my O2 system chatters. None of this gets in the radio, so wall-power buzz won't either.
Power output will be near 10 Watts in 4 ohms and less in 8 ohms. Bigger than a Champ, smaller than a DeLuxe. Plenty to annoy the neighbors. Not enough to play the Palladium. Going to higher voltage might double power, but that's not a big difference.
Thanks Taylor, and thank you too PRR (for that detailed explanation).
This is what my build is looking like...
(https://wave.googleusercontent.com/wave/attachment/tiny.png?id=ARdN6ke71&key=AH0qf5zXgSqzL1WaQnjf7ZjiyutNUHgdfQ)
You know, originally my PCB was laid out like that, but then I changed it at the last moment... ;)
That may not be tiny, but it sure is purdy.
Holy moly. I thought I was a minnow before ...
This weekend i finally found time to stuff my Tiny Giant in a standard stompbox enclosure (http://www.musikding.de/product_info.php/info/p582_Box-Type-B.html). Brief testing performed on one Jensen C12Q 35W 8Ω (http://jensentone.com/c12q.php) speaker inside a cheapish cabinet (http://www.4sound.dk/shop/guitar-comboer/riot/sonic-cab12.html) using this 16V 2.2A laptop PSU (http://imagehost.vendio.com/a/35097889/aview/IBM_Adapter_12J1443.JPG). It looks very ordinary by now, so i'll wait with the pictures for later in the process.
Status report so far; It sounds lovely, and very loud! This is exactly what i was looking for :) I of course ran into the 2 vs 3 prong PSU issue. Ensuring proper power makes any noise dissapear instantly. My tests lasted only minutes, so i didn't notice any real heat from the box. I hope to test further in the next few days, beefing up to combine this with some tube preamp.
Cheers
Touché Taylor,
I have since cleaned up the layout a bit. I completely bypassed the TL072 buffer, and the TDA7240A sounds so good on it's own (even on unregulated power), that I don't really plan to use any preamp with it; just plug in the guitar and play "as is". Does anyone here foresee any issues which might arise.
(https://wave.googleusercontent.com/wave/attachment/tiny.png?id=JhNaaz601&key=AH0qf5zkIpbsqGM1b3a3npK-ByQ40Knv7w)
Pretty crazy! I don't think you'll have any problems running it that way.
What sort of volume control are you planning to have? Without the preamp acting as a buffer, you could get some tone-sucking effects if you just stick a passive volume control in front of the amp.
Awesome build!
waltk,
I'm not quite sure what I'm going to do yet. I may attempt to use it as a reverb recovery stage, from the following driver...
(https://wave.googleusercontent.com/wave/attachment/ReverbDriver6.jpg?id=vMckmRk-1&key=AH0qf5x1Aq8XRrbUonFRfmg_XEpidqAUVA)
through the following Doepfer tank...
http://www.analoguehaven.com/doepfer/springreverb/ (http://www.analoguehaven.com/doepfer/springreverb/)
waltk,
Relative to volume control, I think I've figured out what I want to try (note the 560k pot)...
(https://wave.googleusercontent.com/wave/attachment/buffer.png?id=em39CATS1&key=AH0qf5y6UXUUVULnfUMuy2EvnHYYxYYxpw)
QuoteRelative to volume control, I think I've figured out what I want to try (note the 560k pot)...
I don't know enough about tube circuits to comment on this. I've built a ValveCaster and a Dual Valvecaster and tried them both in front a Tiny Giant. They worked great (but I just left the stock TG buffer/preamp in place).
I would say the only thing you need to be concerned about is getting an appropriate output level from your buffer. If it's truly a buffer, you'll be fine. If it adds any boost, you should limit the gain to about 2. The TL072 in the Tiny Giant has a gain of about 2. You definitely don't want to overdrive the TDA7240 to clipping - it's ugly.
-Walt
Good point waltk,
I'm thinking that the schematic which I posted would give a gain slightly under unity, but your comment got me to thinking: "Why not connect the both halves of the E88CC in full parallel operation (with both using a shared plate and cathode resistance at half the value of the single triode)?" Then I could implement a half-gain option by sending the input signal to only one grid, to obtain an approximate gain of 0.4 with less noise and lower output impedance.
Something like this...
(https://wave.googleusercontent.com/wave/attachment/buffer.png?id=9vozlexk1&key=AH0qf5w2V6C2MA1Cn3Cg03jn9ZxdBt3_jQ)
I'm just wondering whether I should ground the unused grid and/or the internal shield, or let one or both of them float.
> note the 560k pot
I've never seen a 560K pot; perhaps 500K?
However, look both ways. The source is tube and a 5K6 pull-down resistor (6K3 with bias). The load is, I assume, the power-stage of the Tiny Giant, which IIRC is 20K input.
As a first guess, the pot could split-the-difference between 6K source and 20K load. 10K9. You could do a detailed analysis and prefer some other number, however "10K" is such a common part that you'll probably end up with 10K.
> connect the both halves ... could implement a half-gain option
Connect two cars together. Push both gas-pedals. They go full speed. Now push just one gas-pedal. Will it go half-speed? Well.... it's complicated, but likely the two cars fight each other, get unstable, skid, flip, or just overheat.
If you are going to heat both halves, you may as well use them. You can run two triodes on the same 750r+5K6 resistors you use for one, or you can go 375r+2K8. If you want "half-gain", divide the output with resistor voltage-divider, not with a tube-fight.
Thanks again, Paul. I appreciate your input.
QuoteI've never seen a 560K pot
Yeah, they're not extremely common.
http://parts.digikey.com/1/parts/1963290-pot-560k-ohm-1-4w-20-side-flat-1624199-7.html (http://parts.digikey.com/1/parts/1963290-pot-560k-ohm-1-4w-20-side-flat-1624199-7.html)
Quote"10K" is such a common part that you'll probably end up with 10K.
I'll keep that in mind; thanks for the advice.
Quotefight each other, get unstable, skid, flip, or just overheat ... a tube-fight
The act of connecting two triodes for parallel operation, has been widely implemented and documented (i.e. Matchless does this -- and others); as has the act of grounding one of the grids while allowing the second triode to draw its quiescent current (i.e. Merlin has written on this -- and others). I'm unaware of any mention of tube-fighting within these scenarios (even with the triodes relatively unmatched): it's not as though I'm attempting to run two thyratron oscillators in parallel.
http://www.springerlink.com/content/q051218341mt4661/ (http://www.springerlink.com/content/q051218341mt4661/)
The datasheet shows that the input resistance of the TDA7240A is 70k minimum, so shouldn't the volume control be from 10k to 100k?
http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1469.pdf (http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1469.pdf)
Simple parallel is fine if you have budget.
The Springerlink citation covers _plate_ loaded stages.
Tying two cathode followers together is different. Bredbord and see
Hi, this seems like a great little project. I'm gonna order a kit pretty soon.
One question, how would I add a on/off indicator light?
You could use a DPDT switch as your power switch. Use one pole to cut power to the amp and the other pole to light your LED. Or, just tap your LED from the power on the board. When you switch the amp on it will light, when off it won't. Make sure to put a resistor in series with LED as usual.
Thanks! Also, is there a power supply I could get from Small Bear Electronics that would work? Would be great if so, cause I am about to place a big parts order from there.
I have bad luck with wall warts. I smoked a circuit once using what I thought we be the right supply.
Quote from: myramyd on August 07, 2011, 03:14:55 PM
Hey Taylor,
I put together my TG yesterday. Hooked it up this morning and the LM338 (literally) exploded immediately.
Exact thing just happened to mine, as soon as i plugged it in. going to try re flowing the joints. :(
QuoteI didn't realize that I had the polarity reversed on the power jack. I wired the power supply plug to be center positive and didn't make the connection that it's the opposite of how pedal PS are wired.
Luckily I didn't blow the replacement chip--it just got fairly hot while I tested voltage and made the realization.
At least it's working now! Lesson learned...
I Guess I should try switching mine too?
How long does it take to get a pcb from you Taylor?
So I just finished building mine. Sounds great. I love the overdrive. Though I'm concerned because the TL072's pin 8 still isn't reading 11 volts. Need I worry?
What voltage are you getting there?
Quote from: Taylor on January 10, 2012, 10:59:32 PM
What voltage are you getting there?
Most of the time, 0. After playing through it for the first time, it started to read something but it shot down afterwards. I wanna say it was 9v but it was probably 1 or -1. It was hard to tell because it was so sporadic. Though I'm a bit of a noob at this so I could be reading it wrong but all the other options I've tried didnt yield anything either. Multimeter set at DCV, 20V would pick up on it right? And you say check this before powering up so does that mean i should have done this before I start playing through it or before I plug in the power, as I don't know where 11v would come from without some power. The amp sounds fine, I just don't know if I'm danger of blowing it up, where to start looking for the the problem or what it even really means.
Right, you definitely need to have the power on to read voltage. Sorry if this is a rude question, but you know that to read voltage you have to touch the black lead to ground simultaneously right? You probably do, just checking.
Quote from: Taylor on January 11, 2012, 04:29:07 PM
Right, you definitely need to have the power on to read voltage. Sorry if this is a rude question, but you know that to read voltage you have to touch the black lead to ground simultaneously right? You probably do, just checking.
Haha, not a rude question at all because I'm all new to this. At first I thought the enclosure was synonymous with ground due to the plastic jack and the lm338t, so it took me a minute but then I figured you meant the ground from the power supply and it read fine! Thanks!
Hi all,
I'm close to getting this guy in its enclosure. I had it out to test it, and it's motorboating like crazy, with the guitar volume up or down.
A couple of possibilities that crossed my mind were:
- the power supply is too close to the amp - it won't be in the enclosure
- the volume, standby and input wires are too long & are picking up RF
Any additional thoughts on what it might be? Thanks in advance.
(http://img856.imageshack.us/img856/8906/tgtestsetup.jpg) (http://imageshack.us/photo/my-images/856/tgtestsetup.jpg/)
Uploaded with ImageShack.us (http://imageshack.us)
Seems like it was the lack of good grounding. After a good night's sleep, I arranged things better, and it was fine. What fun it is!
And boy, that little sucker gets WARM for sure.
Here's my build! I used the carcass of a dead yamaha VX15 amp, gutted it and re-used as much of the original as possible. Mods include a gain control (goes from about 2x - 7x), a speaker out which kills the internal speaker, and a 3 band tone stack as suggested by PRR in a previous post in this thread. I love it, perfect clean volume for bedroom playing and prototyping... can't wait to plug it into my 2x15 cab at the space though!
One quick worry though... the first time I powered it up, I hadn't noticed a solder jump between 2 resistors... the chips immediately got very hot, and I was measuring voltage on pin 8 of the TL072 fluctuating between 8-10 volts. I didn't leave it plugged in that was for long, and I got it fixed up pretty quick... just wondering if permanent damage might have been done to the regulator or amp chips?
Thanks for a great project Taylor!
Here are some pictures:
(http://www.atlaseffects.com/TG/TG1.jpg)
(http://www.atlaseffects.com/TG/TG2.jpg)
(http://www.atlaseffects.com/TG/Guts.jpg)
Tough to say, not knowing which resistors were bridged, but if everything's working right now, you're probably fine. Nice build!
I have a 15v 3A power supply. You think it'll do?
Hi,
Sorry for my english !
To answer Therecordinart, max volt drop of the lm338 is less than 3V. So 15-3=12v. 12v>11,47v. So 15V seems very good if you keep the adjustement resistor of the regulator as given by taylor schematic. The regulator won't get hot ! The current of 3A seems enough, because it as been said on this forum that the functionning current is around 1/1,5A. Maybe a bit low for peaks, but smps recharges really fast their output capacitors.
I've buy a TGA from Taylor. I've got a IBM 16v 4,5A laptop power supply. I got it to make a evolutive amplifier, from simple amp, to multi effect bi-amp cab by adding modules. At the end, the TGA would be use to amplify low frequency after a low pass filter and a sub cut, (and other effects) a with a 2x10" isobaric cab of fane 10-125 (seems a cheap and good solution for lows). But at the beginning of the project, it will be use only with a eminence governor 16ohm.
As it's a big project, I take me time. I like the concepting aspect. So, I don't have yet soldered stuffs, as i would like to try to understand the circuit, and maybe try to make some improvement.
So, since near one month, i interest myself in electronic. I've make a lot of search on forums to make my own opinion about audio power supply. Here is what i've understood with my poor electronic basis :
_First, it seems using a laptop supply is a very good idea to not use transformer. As it operate at very high frequency, output capacitors of the laptop power supply ciruit is recharged at very high frequency, so we don't need to have big reservoir capacitor on power part of the circuit (all before the regulator). The problem should be that it probably emit EMI so that we have to
_Regulators provide a easy way to get a very low impedance output, and this is a very good things for audio amplifiers. But it seems that it need time to detect voltage drop to correct it, wheareas capacitor reservoirs don't needs as they're precharged (but have higher impedance).
So i've got some question. It seems that the regulation could be improved by different ways, and i ask your help about their real utility:
_ adding a capacitor on adjustement pin, as the lm338 documentation suggest seems to improve transient response, noise (tnt-audio site explain it http://www.tnt-audio.com/clinica/regulators_noise2_e.html (http://www.tnt-audio.com/clinica/regulators_noise2_e.html): Noise is reduced tenfold with about 20dB on lm317 or lm337 regulator) and lower the impedance. But it would need as the datasheet explain, a protector diode.
_using the regulator only as a output capacitor charger (for the 470uF capacitor on the circuit) : so capacitors after it would'nt need to support high voltage, and would cost less. Studying capacitors datasheets, it seems that lower voltage capacitors have lower esr...the idea is to putt for example a 0,1R in serie after the regulator, so that the tda current went first from capacitor, wich react faster than the regulator, as it is precharged, and don't need signal error to react to more current demand from the tda. The resistor would protect the regulator against capacitor inductance (i don't really understand this...). But in this way of supplying the tda, to get low impedance at low frequency, i estimate that it is needed to use 4 x 3300 uF panasonic FM capacitors wich have very good esr (0,013@100khz so maybe around 0,05@100hz=>0,0125 for four, near the same impedance of the lm338 without capacitor on adjustement pin) to get good current feeding at low frequency. Moreover, it make a RC filter after the regulator low pass filter below (i don't remember at wich exact frequency i had calculated).
But the problem with this solution is for peak demand of the tda : the use of a 0,1R means proportional volt drop to voltage demand of the TDA. So maybe we would loose a bit dynamic ? Another problem is that the use of big capacitor may require a protection diode for the regulator...and i have understood that diodes increase noise.
The use of the resistance is to prevent the regulator to became non-stable with big capacitors inductance...
I know there is also "snubber" tricks on the web with the lm338 for audio, but it put another resistor on the output reservoir capacitor and reduce so the impedance of capacitor; it don't seems at all a good idea.
To resume, my idea is to use the regulator as a stabilisator so that power came from a big capacitive reservoir with very low impedance as we can use low voltage capacitors, wich are moreover, cheaper. Tweakings would add :
_a 10uf capacitor on adjustement pin (for noise) and a 1n4002 diode protection.
_a 0,1R 10 watt +4*3300uF 16V very low esr capacitors (chosen for the lower esr found in capacitors datasheets and limiting their cost to 8 euros for four).
Total tweaking cost would be less 10 euros, and seems interesting. Maybe other cap could be better, or cheaper, i didn't read all datasheets.
This is all hypothesis based on what i've searched on web, i know it's a esoteric approch of electronic, but interesting.
Does it seems you coherent ? Do you see better / cheaper improvement ? (as providing symetric and powerful supply to the aop maybe...i know it would improve, but i've not already worked on the question)
Thanks,
Damien
> Noise is reduced tenfold
But can we hear the noise now? The simple regulator does have good ripple reduction. The car-amp power chip has very good power supply rejection (a car's electrical system can be VERY noisy).
In most DIY builds, ground layout and wires too close to each other will leak more power supply noise than the chips.
> very good esr ... 0,0125
The elephant in the room is the 3 or 6 ohms of speaker resistance. We want to make other resistive losses "small" compared to 3 ohms. Smaller than 1 ohm. But I would not go to a lot of trouble to get 100 times smaller.
:P
I didn't have any other reference than what i read, so i have mixed lot of different things :D. Thanks for your knowledge !
Ok, so I don't add capacitor on adjustement pin.
I'll add the diode protection and two 6800uf standard caps i have in stock for lows.
Is it useful to add a resistor on the output of the regulator for a story of inductance relation?
Damien
I think it is a very fine design just the way it is.
Thanks again for your experience. I've seen in the forum you make really good advices.
I'll just do as the original circuit. As i said, i (re)discover electronic since few month.
There's so many thread about audio circuit improvements, it seems there is always a lot of things to tweak to make better.
Quote from: PRR on February 09, 2012, 02:52:58 PM
I think it is a very fine design just the way it is.
Thanks Paul. :)
Papasteack, I'm glad that the project has given you a number of ideas. Let us know how your build goes.
As it seems to interest...let's saying more about it...
With 11 different tweaked modules in a Bi-amp home combo, it will be a loooooooooooooooong funny step by step project :
_choosing modules/designing...yet difficult !! I'm still at this step since 2 month ^^
_making the box + TGA to drive a already made 12" bass reflex eminence governor 16 cab
_adding Bloviator (madbean bbe soundstomp clone) + Cupcake (madbean orange squeezer comp)
_adding rebote delay 2.5 (tonepad)
_adding 2x split_blend (runoffgroove) + sabertooth (madbean fuzz)
_adding 10 band tl074 eq (with virtual ground for symetric power cicuit used for the subsaver too)
_making the combo enclosure : 2*10" isobaric fane 10-125 + 12" open back governor 16 ohm (<80l for all) => to be usable either for bass or guitar without compromise
_adding lm386 amp with hexfet preamp (french "mini-mos amp")
_adding 2 way active cross over (sound.westhost) + subsaver (subwoofer-builder)
_adding a distortion (diefet)
(https://lh6.googleusercontent.com/-2EPjetjKaGE/TzUBXdRjPxI/AAAAAAAAAGc/25ibVF-VVGs/s512/bb.PNG)
Here is the first try of design...I don't draw very good, so i did as i can. The idea is to mix CLEAN/DIRT sound. The DIRT beeing itseft a mix between fuzz/disto sound, with or without a high pass for bass use. The big EQ position is selectable : before mixing channels, off, or only on clean channel. Rebote delay, cupcake and bloviator are global effect so they came after in the chain. Output effect are the subcut, and crossover. Tiny giant is for used for low when crossover is selected. The high are amplified with "mini-mos", wich has a hexfet preamp (so only "high" benefit of preamp when crossover is activated, bass are intented to be more conserved). Rebote delay would include infinit mod. EQ, fuzz and disto potentiometers are 9mm models. Position of miniswitch will probably have to be adjusted as i didn't found their datasheets. Crossover frequencies will have to be adjusted. With 10 potentiometer, this is the EQ circuit wich will cost the more (sorry for my english, i write as i can ^^ )
The inside of the box, where cable would pass have been designed yet too making attention to parasite effects between them.
The only missing thing would be a foot pedal sampler/looper...but i think i would buy it if i want one...
Quote from: papasteack on February 10, 2012, 07:19:38 AM
I don't draw very good, so i did as i can.
You sure, looks like you "can" very good, I'd say ;)
well done, I'm working on "something like that", more eeeeeasy.... just an overdrive and chorus, and a cabsim.... couple of months and I'm done ;D ;D
Wow, that will be a great unit when it's done. Looking forward to seeing it.
I have a question about the input. The FAQ for this site suggests a stereo input so that the input can act as a switch. This build shows a mono input. It seems to me that switching via the guitar input isn't necessary (or even desired). Am I correct that the mono input is a better choice for this particular build?
While I'm at it, I plan on building a couple of effects pedals (probably an orange squeeze and a tube screamer clone). These both need 9V, but it looks like I have 11.6 volts in the circuit (since I'm asking, the power input can be between 15-20 V - but the schematic specifically says 11.6 - I'm guessing this is a precisely controlled voltage).
Can I just run the 11.6 from the output? With the voltage drop on two pedals, will the couple of extra volts do any damage or change the nature of the effect? Is a voltage divider overkill for the sake of two and a half volts?
QuoteI have a question about the input. The FAQ for this site suggests a stereo input so that the input can act as a switch. This build shows a mono input. It seems to me that switching via the guitar input isn't necessary (or even desired). Am I correct that the mono input is a better choice for this particular build?
Yes, a mono jack is better for this. Switching the power by using a mono plug into a TRS jack is a convenience in pedals that are battery-powered. It saves the battery and/or allows you to eliminate a separate power switch. In this case, the power is always external, so the reason for doing it doesn't apply.
Also, I would be concerned about switching a lot of power (as required by this amp) this way. Here's why... Using the TRS switching method, you normally connect the power ground to the ring of the jack, and the circuit ground to the sleeve. When the mono plug is inserted the one long stretch of plug connects the ring to the sleeve, and completes the power circuit for the effect. The problem is that there's a moment (fractional second) while you're inserting the mono plug when the tip of the plug is in contact with ring of the jack, and the shaft of the plug is in contact with the sleeve. This would momentarily try to complete the power circuit through the device that is connected to the plug (maybe a guitar or other effect). Do you really want to expose the device to a jolt of 15 volt/4 amp power?
QuoteWhile I'm at it, I plan on building a couple of effects pedals (probably an orange squeeze and a tube screamer clone). These both need 9V, but it looks like I have 11.6 volts in the circuit (since I'm asking, the power input can be between 15-20 V - but the schematic specifically says 11.6 - I'm guessing this is a precisely controlled voltage).
There are a couple other posts in the thread about powering other pedals using the TG voltage regulator output. I would use an additional 7809 regulator for this, and power the other effects in parallel.
Thanks. I am documenting my build as I go (I didn't get the printed circuit yet, so I'm starting with other components).
I want to etch the enclosure, so I started with wet sanding. The bottom of the enclosure is the factory finish, and the top is sanded (220, 400 and 1000 wet sand paper)
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC01958.jpg)
My first solder joint was on the pot. Looking at the terminals, I think I got the pot designed to be placed directly onto the board. I want to use wires so I have freedom to place the pot wherever I want.
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC01959.jpg)
Here are the LED, switch and pot soldered and insulated with heat shrink.
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC01960.jpg)
I had designed my graphic earlier this week. Before I altered the enclosure, I decided to glue the printed graphic to a piece of cardboard and check the fit of the components. As you can see, I didn't leave enough space between the switch and the pot.
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC01962.jpg)
Here it is from behind. My wiring looks pretty deep - I'm nervous about how much space these three components will take.
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC01963.jpg)
Here it is with the pot moved north. I like the aesthetic of the three components, but it messes with my graphic. My daughter's name is Victoria, and since this project is based on Taylor's Tiny Giant, I thought I'd make a play on my baby girl's name and her sharing a name with Queen Victoria (with a nod to Freddy Mercury in there as well). If I want to keep the name "Tiny Queen", I'll have to find a spot that looks right.
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC01965.jpg)
Quote from: waltk on February 11, 2012, 11:07:03 AM
There are a couple other posts in the thread about powering other pedals using the TG voltage regulator output. I would use an additional 7809 regulator for this, and power the other effects in parallel.
I found another link on the 7809. It suggests that it should have .1uF capacitors on the input and output sides. The schematic doesn't state polarity, so can I use a ceramic cap? It also doesn't state the voltage - probably a 20V?
QuoteI found another link on the 7809. It suggests that it should have .1uF capacitors on the input and output sides. The schematic doesn't state polarity, so can I use a ceramic cap? It also doesn't state the voltage - probably a 20V?
Rules of thumb:
You can always use a non-polar cap of the correct capacitance whether the circuit specifies a polar or non-polar one (the converse is not true - don't use a polarized cap if the circuit calls for a non-polar one).
Always use a cap that is rated for more voltage than it will see in the circuit - it doesn't matter how much higher.
If the cap is in the signal path, film caps are usually preferred - in this case, it doesn't matter.
Within these general rules, the choice of caps is usually determined more by size and cost. It's rare to find a stompbox circuit that
doesn't use .1uF caps - so you should consider buying a quantity of nice .1uF film caps. They're cheap and readily available in 50V or 100V ratings with 5mm lead spacing.
This amp looks amazing! And in fact, just what I've been looking for. After building a few ruby variants, I've wanted to build something with a bit more oomph, but being relatively new to the game, I'm not ready to risk my life with high voltages. So, I have read this whole thread and have a couple of questions. I think I know the answers, but really I'm not sure, so I hope someone here will take pity..
The first is very noobish (sorry) and kind of general. Regarding power supplies, if you have a 4A supply as is recommended here, does that mean it's pushing 4A into your circuit, or is it that there is up to 4A on tap if the circuit needs to draw it? Or something else. Sorry again for my limited grasp of electrical basics. I tried to answer this question through my own research but don't even really know how to phrase the question so it makes sense, so I hope someone can guide me here.
Secondly, considering the 4A power supply, would I be able to put something such as the Matsumin Valvecaster into the same build to act as a pre-amp? i.e. will 4A cause damage to a circuit that only draws a few hundred mA? I've built a couple of valvecasters, but the strip board I build the circuits onto is only rated at about 1A.
Sorry again if these questions are infuriatingly basic, but I would rather ask than build something that will explode.
QuoteSo, I have read this whole thread and have a couple of questions.
Welcome, and congratulations on reading the whole thread.
QuoteSorry again if these questions are infuriatingly basic, but I would rather ask than build something that will explode.
Questions are good - especially after reading the whole thread.
Quoteif you have a 4A supply as is recommended here, does that mean it's pushing 4A into your circuit, or is it that there is up to 4A on tap if the circuit needs to draw it?
It means that there's up to 4A on tap if the circuit needs to draw it. Power supplies try to give what the circuit demands, rather than push current through them. The TG draws about 1A on startup, then less than that depending on volume.
Quotewould I be able to put something such as the Matsumin Valvecaster into the same build to act as a pre-amp?
Yes. The biggest consumer of current in a valvecaster is the heater - about 150ma. You can run the valvecaster off of the regulated voltage from the TG.
Quotei.e. will 4A cause damage to a circuit that only draws a few hundred mA?
No. Your valvecaster will draw what it needs and no more.
Also, because the default TG build sets the LM338 regulator to produce 11.6V, you should make one resistor change so that it produces 12 or 12.6V to power the Valvecaster tube heater. The tube heater will like this voltage better, and it won't hurt the TG.
Oh cool, thanks for your reply, that's what I was hoping to hear. Although I hadn't figured the fact of needing to increase the voltage to ~12V so thanks for the heads up on that!
Quote from: PRR on February 09, 2012, 12:52:00 PM
> Noise is reduced tenfold
But can we hear the noise now? The simple regulator does have good ripple reduction. The car-amp power chip has very good power supply rejection (a car's electrical system can be VERY noisy).
In most DIY builds, ground layout and wires too close to each other will leak more power supply noise than the chips.
> very good esr ... 0,0125
The elephant in the room is the 3 or 6 ohms of speaker resistance. We want to make other resistive losses "small" compared to 3 ohms. Smaller than 1 ohm. But I would not go to a lot of trouble to get 100 times smaller.
Hi,
I come back about optimizing the regulator. I have understand a bit what is supply rejection...So, the tda has a very good sypply rejection...But what about the tl072 ? And other circuit that should be connected to the regulator ?
So the need of capacitor on adjustement pin should be justified at leastd for the buffer, and for other circuits. And overall, if there's a distortion circuit with a lot of gain... Am i right?
Damien
Hi all, a frustrated newbie question here.
I have the TG working by itself, but can't get the stompbox I built into the cab to work without patching it. My setup is as follows, following RG's article (http://www.geofex.com/article_folders/jiab/jiab.htm):
Input --> stompbox --> stompbox volume lug2 --> tip of NC jack 1 (preamp out)
|
switch of NC jack 1 --> switch of NC Jack 2 (amp in)
|
--> tip of NC jack 2 --> TG in
If I patch Preamp Out --> Amp In, it works. If I pull the patch, it doesn't. I can't figure out what I'm missing here!!
Thanks in advance for any advice!!
Well, even though I've yet to figure out my NC jacks, I wanted to post my 99.9% completed build for you to see:
(http://img638.imageshack.us/img638/3275/familyn.jpg) (http://imageshack.us/photo/my-images/638/familyn.jpg/)
The build thread is here:
https://picasaweb.google.com/101724142776681014815/LittleBluesAmp?authuser=0&feat=directlink
It's real interesting sounding with the Supreaux front end & the 6x9 speaker - this is not a shredmeister setup!!
I can also bypass the front end & either plug directly into the TG, or plug my Amplitube into it. The 6x9 speaker definitely gives a different twist on the sound.
It's a spanking little setup for home practice, and I may have to take a day off work this week to have some fun.
Thanks everyone for the good knowledge & advice!
Looks really cool! If you can post a picture of the jacks you're having trouble with, and the way you've wired them, perhaps we can figure out the problem.
Thanks for the compliment, Taylor!
I'll try to post pictures towards the end of the week - pretty busy ATM.
I just got my kit. Before I start heating, I want to check. Under the tl072 there are two holes. Do I leave these empty, and just solder the 8 pins of the socket here?
I went ahead with it, but I'm having some problems. As indicated in the instructions, I checked to ensure the speakers and the heat sink tabs were not continuous with the ground. They were- everything is.
I was careful and thought I'd be ready to try this, so I had everything assembled. I slowly began disassembling to look for the problem.
I'm not sure if photos will help. I fear there's a short somewhere in my soldering. I'm using the resistance setting of my multimeter to test for continuity and I'm seeing real values (i.e. not infinite resistance) on just about everything I test.
For example:
I get 3K ohms when I test across the ground and +ve in.
I get 0 ohms when I test from ground to the sleeve of the input jack (I expected this).
I get 1100 ohms when I test from ground to LM338 tab (that's removed from the enclosure)
I get .9 ohms when I test from ground to the tab of the TDA
From ground to the red lead of my speaker I get infinite resistance, but from ground to the black lead I get a quick reading that then goes to infinite.
From the red lead to the black lead of my speaker outputs I get 7.68K ohms.
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC02018.jpg)
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC02020.jpg)
Since there are caps and resistors connecting all areas of the circuit, it makes sense that you will not see infinite resistance between all areas of the circuit, right? As long as your meter does not read 0 ohms you are ok to assume two things are not continuous. But I would also recommend getting a multimeter with a beep-continuity mode. I got one for about $12 I think.
The two small holes are called "vias". They are there as part of the internal circuit board design - they connect traces on the bottom copper side to traces on the top. ou don't need to do anything with them, just ignore them. Don't connect them to anything.
Thanks; that's good to know. I was worried because I was careful and took my time- I couldn't figure out where I went wrong. I'll probably get a chance to finish wiring it up tomorrow and fire it up.
It works! Thanks guys. Taylor and everyone. I have never done any type of electronics prior to this - Taylor, your kit was a breeze (despite a few panic moments; but that's my issue, not yours). From enclosure etching to soldering and understanding the circuitry; this was a group effort between my and DIT stomp boxes.
I have a couple of suggestions for future builders. The two IC's that have the heat-sinks that attach to the wall of the amp are tall - in my case, I didn't sink them quite low enough on the PC which means they are in the way of my base. I can easily shave the base back, but it would have been nice if I had made it just a bit shorter.
I also decided to use an old plastic gift card as an insulator pad under the IC. I put a layer of electrical tape over it - mostly to obscure the store logo from the gift card.
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC02026.jpg)
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC02027.jpg)
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC02028.jpg)
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC02029.jpg)
(http://i56.photobucket.com/albums/g191/Doc_Roadster/DSC02030.jpg)
I plan on putting in a 9v regulator on the out, and making a DC out to attach a pedal. I also need to clean up my DC in.
On that note, my laptop DC has something attached to the cord on the DC side (it's a small cylinder - smaller than a size C battery). I have noticed this on multiple AC to DC converters on the DC side. What is it? I already cut the stock end off and soldered my power end, but I want to replace it. Cutting it again will put me very close to this widget.
Quote from: DocAmplify on February 24, 2012, 07:26:21 PM
On that note, my laptop DC has something attached to the cord on the DC side (it's a small cylinder - smaller than a size C battery). I have noticed this on multiple AC to DC converters on the DC side. What is it? I already cut the stock end off and soldered my power end, but I want to replace it. Cutting it again will put me very close to this widget.
A ferrite bead perhaps?
http://en.wikipedia.org/wiki/Ferrite_bead (http://en.wikipedia.org/wiki/Ferrite_bead)
Yes. It is so close to the end that I worry that I'll have to cut it off if I modify more, but it sounds like a useful addition to the power line.
So ... my amp is now 100%. I had labeled one of the NC jacks with a piece of masking tape, and part of it must have slipped between the switch & tip contacts, preventing it from completing the circuit without patching it. It's working great now.
Here's my Tiny Giant build. It sounds awesome even without a preamp. Taylor's PCB (http://musicpcb.com/pcbs/tiny-giant-amp/) soldered together in about 10minutes. It's in a crappy faux train case with a Jensen Mod 10". Plenty of room left for my lonely, dusty spring reverb unit. I hope the speaker doesn't vibrate the unit too much. The box is light, so I'm sure it will, but I'm gonna try anyway.
(http://farm8.staticflickr.com/7187/6941802075_05b8afbd1d.jpg) (http://farm8.staticflickr.com/7203/6941870463_9f0622842f.jpg)
I like it. 8)
This may speak to my total confusion here, but I've searched and can't find the answer.
Does the Tiny Giant have a preamp and an amp section?
My goal was to plug my guitar into the tiny giant and then go out to my cabinet.
I notice that many of the effects pedals have amplifier sections (op amps or transistors). If you use an overdrive or distortion could you consider this a preamp, or am I misunderstanding?
Personally, I would just build the Tiny Giant, plug your guitar in, play with it for a minute, and judge from there. Maybe like me, you'll find it sounds great the way it is. I don't mind schlepping pedals around, so it doesn't bother me that the circuit is bare-bones.
The TL072 is a preamp/buffer for the TDA.
Also, I would make CERTAIN everything passes the continuity test before trying it with your cab. Do you have a cheap speaker laying around?
QuoteI like it. Cool
Thanks dude!
Yes. I tried it through an old car speaker, then through a TV sound system speaker, then my cab.
If the TL072 is acting as the pre-amp, then am I correct in assuming that the only reason for another pre-amp would be for tone control (as opposed to actually boosting the signal).
If that's the case, then would a cab simulator like the Condor (or Marshall modified Condor) serve the purpose of adjusting the tone quality? Or would that make changes that then get further changed when it hits the actual cab?
I'm thinking about building a Condor cab sim modified with the Marshall dip so I can put my guitar directly into the mixing board, but if it could piggy back on the Tiny Giant on occasion, then I'm all for multi-tasking.
The TG does have a basic clean preamp at the beginning, so you can definitely plug your guitar straight into it. The only reason to add another preamp or pedal is to get a particular sound.
If you replace the 220k resistor with a 1m pot, then put anti-parallel diodes in parallel with the pot, you could have some variable TS-style distortion/overdrive. Adding some tone shaping after that would probably be preferable to most people, but it's all a matter of personal preference. Some people have posted their thoughts on adding tone stacks to the TG in this thread.
I would build the cab sim as a separate unit, because you won't generally need a cab sim when using an amp into a real cab. If you were going to record to a desk while also playing back through the TG and a cab, it would make most sense to split the signal with an active ABY or something, then run to the two devices.
Hi there
built a second one, for a new fun project.... while the first one worked the first time I've turned on, with this one I've problem..... I've no sound at the speaker, just noise, almost like when gnd is missing, there is sound there, I can hear it, but completely covered by the noise. I'va taken some voltage readings, here they are
PSU - 19.40
TL072
1 - 5.96
2 - 5.96
3 - 4.06
4 - 0
5 - 4.07 ?? on Taylor pdf it states 11.6!!
6 - 5.79
7 - 5.99
8 - 11.82
LM338 facing from the front
10.58 11.83 19.39
TDA facing from the front
1st row of 3 pins
11.82 - 0 - 5.38
2nd row of 5 pins
5.59 - 5.55 - 4.83 - 5.56
I've changed already 6/8 TL072 with the same results.
Compared this board with the working one... everything seems to look the same
Pitcture of the board
http://i256.photobucket.com/albums/hh174/arma61/SNC00019.jpg
Any idea on what could be wrong ? there's no way I can get more than 4.7V at pin 5, it this the problem ??
Thank for help m8s!!!
Ciao
Armando
Quote from: arma61 on March 18, 2012, 12:40:30 PM
PSU - 19.40
TL072
1 - 5.96
2 - 5.96
3 - 4.06
4 - 0
5 - 4.07 ?? on Taylor pdf it states 11.6!!
6 - 5.79
7 - 5.99
8 - 11.82
Any idea on what could be wrong ? there's no way I can get more than 4.7V at pin 5, it this the problem ??
Thank for help m8s!!!
Ciao
Armando
I get the same voltages and mine works.
Both pin 3 and 5 are the non-inverting inputs. If you look on the schematic pin 3 is fed 11.6V through a voltage divider that reduces the voltage by half so your pin 3 is correct.
If you look on the PCB, pin 3 and pin 5 are connected so they should read the same.
I can't help tell you what's wrong but I don't think your problem lies within the tl072.
The PDF might be confusing. I think the TL072 side named U1A in the schematic is pin 5, 6 and 7 (pin 8 gets 11.6V and 4 goes to ground). I base this on the fact that by looking at the PCB it looks as though pin 7 is connected to pin 6 through the 220k resistor and pin 1 and 2 are tied together (like shown in the part named U1B).
Maybe Taylor can shed some light on the subject.
Pin 5 is actually connected to pin 3 and therefore driven by the input signal and biased to the center of the power supply. That opamp is not being used and this is just a way to hold it near the center of the supply to avoid drawing a lot of current.
So, that's a mistake in the schematic. There was an error in the voltages at one point, which I corrected, but it looks like in correcting that I created a new error. In other words, there should NOT be 11.6 at pin 5.
I don't see anything obviously wrong in your voltages, so my guess is that there is just an open circuit somewhere in your audio path. I would recommend audio probing to see where the signal is getting stopped.
Quote from: Taylor on March 19, 2012, 06:58:04 PM
Pin 5 is actually connected to pin 3 and therefore driven by the input signal and biased to the center of the power supply. That opamp is not being used and this is just a way to hold it near the center of the supply to avoid drawing a lot of current.
So, that's a mistake in the schematic. There was an error in the voltages at one point, which I corrected, but it looks like in correcting that I created a new error. In other words, there should NOT be 11.6 at pin 5.
I don't see anything obviously wrong in your voltages, so my guess is that there is just an open circuit somewhere in your audio path. I would recommend audio probing to see where the signal is getting stopped.
Sometimes, I find it hard to know when there is an error somewhere or wether it's just my lack of knowledge keeping me from understanding things. But just for my own understanding, am I correct in thinking that the U1A part is pins 5, 6 and 7 making the U1B pins 1, 2 and 3?
I'm used to thinking of opamps as a record, "A" being the first side (1,2,3,4) and "B" being the second side. That's why I'm asking.
I would also like to take this oppertunity to thank you Taylor. I have built two of these using your kit and they have both been great. Much appreciated!
Hey guys thx for help...
T I don't see anything obviously wrong in your voltages, so my guess is that there is just an open circuit somewhere in your audio path. I would recommend audio probing to see where the signal is getting stopped.
That's good to know, this mean I didn't mess up with the important components (btw I hat those resistor :icon_mrgreen: having a cheap&old multimeter it's quite hard to take their value!!!).
I will have a go with the audio probe in the next days and report, quite sure, being the voltages right, it's something stupid... so better I leave it sitting there for a while...........
Thanks again
Ciao
Hey guys I'm just breaking into this whole pedal thing and I wanted to run some ideas by you guys and see if you could help me make them happen.
We all know that tubes being driven sound great. And that ss amps have awesome cleans but if driven to hard can make a really bad sound.
What I wanted to know is...
would it be possible to use a tube circuit like the "valve-master" and wire it up to this SS amp with some kinda limiter/buffer between them so that no mater what the settings on the valve-master were, the "Little Giant" was feed a relatively lower output signal level.
This way The valve part of this new amp could be driven as hard as you want, getting all the goodness that tubes can offer, while the SS section didn't clip and was allowed to push out a good signal inside it's normal range.
Would this be as simple as a slight compression circuit or just setting the Valve-Master up as if it volume pot was turned much lower(like around unity gain), and have the only control from it be the gain knob?
Would this work? I mean if it did it might just be the greatest Tube/SS hybrid amp you could make for around $70USD
Quote from: Ark Angel HFB on April 04, 2012, 03:21:17 AM
Hey guys I'm just breaking into this whole pedal thing and I wanted to run some ideas by you guys and see if you could help me make them happen.
We all know that tubes being driven sound great. And that ss amps have awesome cleans but if driven to hard can make a really bad sound.
What I wanted to know is...
would it be possible to use a tube circuit like the "valve-master" and wire it up to this SS amp with some kinda limiter/buffer between them so that no mater what the settings on the valve-master were, the "Little Giant" was feed a relatively lower output signal level.
This way The valve part of this new amp could be driven as hard as you want, getting all the goodness that tubes can offer, while the SS section didn't clip and was allowed to push out a good signal inside it's normal range.
Would this be as simple as a slight compression circuit or just setting the Valve-Master up as if it volume pot was turned much lower(like around unity gain), and have the only control from it be the gain knob?
Would this work? I mean if it did it might just be the greatest Tube/SS hybrid amp you could make for around $70USD
Most of what sounds awesome about (classic) driven tube-tone is over-/hard-driven Power Tubes; more modern tones typically involve preamp distortion (hence, 4+ 12A_7 tubes in modern preamps) instead of (just) power tube distortion. This isn't to say NO power tube distortion is there; just that the majority of that tone is not from over-driven el34/6l6/kt88s/etc., which is why most modern tones are (slightly) easier to achieve w/o stadium volume or attenuators.
So yes and no; yes, in that you could have a rockin' preamp OD in the situation you describe, and no, you wouldn't have the
typical definition of awesome "tube-tone."
try it out, see if you like it; this is all that
really matters, no?
You can definitely do that. I think it's a good idea and I actually think a few people have already done that with the TG. A couple of caveats/notes:
-I am not really a tone fiend, but my guess is that few people would consider the Valvecaster to be representative of good tube amp tone. I think it's pretty cool for a 12v circuit, but nothing like your favorite tube amp clipping.
-Much of what people like about tube amps is power amp distortion, not preamp distortion.
-I don't think you should take it as gospel that "tube amps sound great distorting, SS amps sound bad distorting." IMO this is one of those memes that gets spread without people listening with their own ears. I have rarely been able to crank the TG as it's too loud for most of my play situations, but I have been told by two different guitarist/recording engineer/golden-ears that the TG distorts in a pretty interesting way. It's not necessarily like your favorite tube amp, but it's not hard clipped square waves. My father did a delta blues gig with a TG I built, playing his resonator guitar through it. Most people thought he was getting a great bluesy driven tone, and it was all TG.
Again, I don't want to dissuade you at all because I think a Valvecaster in front of a Tiny Giant is a great idea and would be a fun rig. I would just recommend checking out the amp by itself first, and making up your mind based on your own ears. :) Nobody on the internet knows better than you do what sounds good to you.
It's true though, that slamming the front end with a booster won't sound good because you'll just be clipping the opamp in front, not the amp itself. So if you do the Valvecaster you might want to bypass the TG's preamp.
Quote from: Taylor on April 04, 2012, 04:15:43 AM
You can definitely do that. I think it's a good idea and I actually think a few people have already done that with the TG. A couple of caveats/notes:
-I am not really a tone fiend, but my guess is that few people would consider the Valvecaster to be representative of good tube amp tone. I think it's pretty cool for a 12v circuit, but nothing like your favorite tube amp clipping.
-Much of what people like about tube amps is power amp distortion, not preamp distortion.
-I don't think you should take it as gospel that "tube amps sound great distorting, SS amps sound bad distorting." IMO this is one of those memes that gets spread without people listening with their own ears. I have rarely been able to crank the TG as it's too loud for most of my play situations, but I have been told by two different guitarist/recording engineer/golden-ears that the TG distorts in a pretty interesting way. It's not necessarily like your favorite tube amp, but it's not hard clipped square waves. My father did a delta blues gig with a TG I built, playing his resonator guitar through it. Most people thought he was getting a great bluesy driven tone, and it was all TG.
Again, I don't want to dissuade you at all because I think a Valvecaster in front of a Tiny Giant is a great idea and would be a fun rig. I would just recommend checking out the amp by itself first, and making up your mind based on your own ears. :) Nobody on the internet knows better than you do what sounds good to you.
It's true though, that slamming the front end with a booster won't sound good because you'll just be clipping the opamp in front, not the amp itself. So if you do the Valvecaster you might want to bypass the TG's preamp.
Well to be honest I've built the valve caster and my first thoughts were how I wish the sound I was getting could just be my amp... the TG seems like an easy solution to my wishes... this brings me to my next "no nothing but would be cool" question.
Would it be possible to build two TG's and wire them some how for push pull operation resulting in a, roughly speaking I know, 40W power amp section?
Could this be done by simpling spliting the signal after the Valvecaster stage, running like stereo into both TGs then joining the TGs possitive and negative leads together before going into what ever speaker(s) you wanted?
Or would this result in some kinda horrible mushroom cloud. XD
Also I was reading along and did we ever find out what was causing the shocks with a PA system? was it just the 48v phantom power or the fact most PA use AC while the TG and guitars use DC. I've got a shock before with 48v Gear when I was playing a poorly grounded amp... would there be a way to ground the TG without messing up what it does?
EDIT: OR... would it be as simple as changing the Amp IC up to something that puts out more?
I only ask because the Amp you listed is obsolete at Mouser and they don't sell it any more... what would be a good substitute?
thanks btw for such a fast response... you are great dude. ^_^
There are places on the web that sell the amp chip. Of course, it comes in the kit I sell on my site, but if you don't want to buy that, a Google search for the chip should find a few places.
You can't make a bridged amp with 2 Tiny Giants because it is itself a bridged amp. What you can do is split your signal and parallel them into 2 speakers. This is good because doubling your wattage only creates 3db more volume, which is barely perceptible. So you'd be doubling your work effort for almost no gain in loudness. But adding another speaker adds 3db of its own, so a second amp into a second speaker would be more worth it than just doubling wattage.
AFAIK the shocks are nothing specific to the TG. Any time your PA and your amp are on different circuit breakers, there is a chance of a ground potential between them. So this has to do with the wiring in some houses/clubs. It's not an AC/DC thing because all music gear that plugs in receives AC and then turns it into DC.
Quote from: Taylor on April 04, 2012, 04:52:07 PM
There are places on the web that sell the amp chip. Of course, it comes in the kit I sell on my site, but if you don't want to buy that, a Google search for the chip should find a few places.
You can't make a bridged amp with 2 Tiny Giants because it is itself a bridged amp. What you can do is split your signal and parallel them into 2 speakers. This is good because doubling your wattage only creates 3db more volume, which is barely perceptible. So you'd be doubling your work effort for almost no gain in loudness. But adding another speaker adds 3db of its own, so a second amp into a second speaker would be more worth it than just doubling wattage.
AFAIK the shocks are nothing specific to the TG. Any time your PA and your amp are on different circuit breakers, there is a chance of a ground potential between them. So this has to do with the wiring in some houses/clubs. It's not an AC/DC thing because all music gear that plugs in receives AC and then turns it into DC.
I will be honest... despite wanting to find stuff as cheap as I can... I can only assume you are making between $6 and $10 bucks per amp kits... and with how helpful you are, and how much you back up you work I'd rather would rather buy your kit than source the parts myself and vero it... I think people who do good work should get paid.
@Ark Angel
buy the kit, you'll be happy you did when you're playing through it 15 minutes after getting it in the mail
Ok just ordered it...
To be frank I'm halfway flirting with the idea of become a part time custom order pedal maker / tube maker...
I'm hesitant even mentioning this as it almost feels like people who do this are frowned upon on these forums.
But I think that comes one from the fact most people here know how cheap it is to make a pedal... and how over priced everything is that companies sell.
It is one reason why I just bought the amp I did is because one, I can learn how to make it first hand... and second... he didn't charge $30 to $40 for the kit like most would have... The fact he didn't try and run the price up on people is a show of both character and goodwill and is a sign of person who deserves to be paid for their quality work.
/mini-rant.
Nobody has any problem with you (or anyone) building things for sale. There are many people on this forum who make some or all of their living from building effects or amps. What many people do object to, is when people come here, take DIY projects, and then sell them without asking permission or compensating the designer - or, in general, cashing in on other people's work. People also object to those who want others to do their homework for them. This is true in any discipline.
I started to write some "personal advice" on a custom electronics business, but it was going to be too long and boring. Short version: you might find that you spend more time emailing about what the person wants than it takes to build a pedal. IME you might find yourself making much less than minimum wage when you do the real math.
Nobody's going to object to you becoming a big star in the pedal biz. :) But I suggest that you forget the dollar signs for now, build a ton of things for your friends for free, to their exact specs, then reassess once you have a better idea of what goes into it. If you think most pedals are overpriced, you may have a lot to learn about business.
No my main thought has more to do that if you make a product for $50 you should's charge over $150.
I know it sounds odd but I'd rather sell twice as many at half the price so more people can have good effects and amps and what not. This is coming from a Former guitar teacher who had the displeasure of seeing people(mostly kids) come in with a lot of excitement, and then be held back by bad gear. It was such a horrible feeling looking at a kids/people who had practiced hard and were doing a chords perfectly but due to cheap instruments or amps... were sounding really bad. Actually seeing enthusiasm die in a person is a completely crap.
I gave lesson for cheap, around $10 to $15 hour, and if I make pedals I'm sell them for cheap.
Don't get me wrong I like making money... but I don't think I could live with myself if I started just another company that made good stuff and then kept it outside of people just starting out by charging more than it is really(massively subjective word) worth.
anyway to stop derailing this thread. ::)
I've been looking at a few PS for this little amp and have a few I'd like to get your opinion on. I specifically found some that seem to have a good supply behind them so that if anyone else wants one of these there should be plenty for a good long time.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190426611359+&item=190426611359&lgeo=1&vectorid=229466#ht_3219wt_1185
http://www.amazon.com/PA3048U-1ACA-PA3282U-1ACA-PA3282U-2ACA-pa3260u-1aca-Satellite/dp/B001MQ35EY/ref=sr_1_12?s=pc&ie=UTF8&qid=1333599515&sr=1-12
The second one is better since it is 15v. Technically the 12v would be fine but you'd want to bypass the voltage regulator on the board. For those just getting started, who don't want to mess with modifying things, I'd recommend the 15v one.
Quote from: Taylor on April 05, 2012, 01:00:25 AM
The second one is better since it is 15v. Technically the 12v would be fine but you'd want to bypass the voltage regulator on the board. For those just getting started, who don't want to mess with modifying things, I'd recommend the 15v one.
Well crap a duck... I could when I was linking them that they were both 15v. XD
was looking things over and I think a cool mod / adition to this that wouldn't be to much trouble would be an effects loop... maybe even get fancy with some kinda foot switch option or something... I do so love being fancy. ::)
It would be added just before pin 3 of the TDA7240A, or am I missing something.
Maybe try building one of runoffgroove.com (http://runoffgroove.com/articles.html)'s amp-turned-stompboxes as a pre for your TG, then no need for an effects loop, and you'll get some real guitar amp-y tone, too.
Question RE: Tiny Giant P/S - I haven't looked at the supplies that others are buying, but I rounded up a couple laptop P/S last night and they all had what appears to 4.5mm jacks. Has anyone sourced a P/S that fits in 4mm or is everyone just buying the 4.5mm Kobiconn?
For one of mine I cut off the supply's plug and wired in a regular 2.1mm (internal dimension) plug for interfacing with a standard (for pedal use) 9v jack.
However, I feel that this is probably not best practice, since you now have multiple power supplies which are electronically incompatible (your pedal supply and your amp supply) but which can physically be interchanged. Potential for bad things. Probably smarter is to buy some unrelated plug and jack that you would never use for anything else. That way your amp supply can't plug into anything into which it shouldn't.
Depending on space you can also simply wire the supply directly to the amp PCB if you are mounting them together inside an enclosure.
Quote from: arma61 on March 20, 2012, 03:38:28 PM
Hey guys thx for help...
T I don't see anything obviously wrong in your voltages, so my guess is that there is just an open circuit somewhere in your audio path. I would recommend audio probing to see where the signal is getting stopped.
That's good to know, this mean I didn't mess up with the important components (btw I hat those resistor :icon_mrgreen: having a cheap&old multimeter it's quite hard to take their value!!!).
I will have a go with the audio probe in the next days and report, quite sure, being the voltages right, it's something stupid... so better I leave it sitting there for a while...........
Thanks again
Ciao
Hi there
happy to report I'm now an owner of 2 working TGAs !! :) :) :)
There problem was, most probably, related to the stuff I used to test it, signal coming from an old walkman powered by a not-so-well-filtered wallwart... (bored to keep on changing batteries 'cause I leave it on everytime :icon_mrgreen: :icon_mrgreen: ), so when I connect the right speaker and the guitar it works as it's supposed to!!!
Thanks again m8s for help and again to Taylor for this fab little amp.
Have a nice day!!!
Ciao
Glad to hear it Armando!
I guess I meant 2/2.5 mm not 4/4.5. Anywho, you seemed to take my meaning and answered my question. Thanks Taylor!
No, you might well be right about that - they have an internal dimension and an external dimension. I always forget the external dim of the standard pedal jack, but I'm sure it is somewhere in the range of 4 or 5mm.
Ok so here are some things to consider / help me out with... 1 you might want to go ahead and give a heads up about the kit not including the 10k pot... just saying I was getting ready to build this it tonight then had to go aaa crap... I don't have a part. it isn't a big deal. they are $1 off ebay with free shipping so it is on it's way... but it was a bit of a disappointment to have to wait. XD
You may want to redesign or maybe just leave a bit more room so that the 1k resistor is swapped for a 1k trim pot with a 500ohm resistor in series after it. This would allow people to dial in the volts/power output they want as well as protect against it going over the 1.5k limit you suggested.
Just saying these are two changes that might make this an even better product. ^_^
In the same vein as the second thing mentioned above I'm planing on combining this with a ValveMaster which I would like to run at 12.5vDC.
I'm using a 15vDC 4A Power supply so...
A. what value should the 1k resistor change to to give me a steady 12.5vDC.
or
B. Simply tell me how to do the calculation and I will do it myself so it is not like I'm just asking for all the answers in the world. XD
Quote from: Ark Angel HFB on April 18, 2012, 12:24:59 AM
Ok so here are some things to consider / help me out with... 1 you might want to go ahead and give a heads up about the kit not including the 10k pot... just saying I was getting ready to build this it tonight then had to go aaa crap... I don't have a part. it isn't a big deal. they are $1 off ebay with free shipping so it is on it's way... but it was a bit of a disappointment to have to wait. XD
Hmm, ok, this is tricky because I do state precisely everything that comes in the kit, but not what doesn't come in the kit. The reason it doesn't come with the pot is that there a million different types and every person will want a different one (9mm for 1590a builds, 25mm for heavy duty amp guys/solid shaft, knurled shaft...). This is also why the kit doesn't come with an enclosure, knob, heat sinks, etc. But I definitely see how that could be confusing and a little annoying for somebody who doesn't know quite what they need. I will think about how to solve this.
Quote
I'm using a 15vDC 4A Power supply so...
A. what value should the 1k resistor change to to give me a steady 12.5vDC.
or
B. Simply tell me how to do the calculation and I will do it myself so it is not like I'm just asking for all the answers in the world. XD
No problem asking questions, however now is a good time to learn that about datasheets! :) Every part in the world has a datasheet, and it knows more about the part than even the legends on this forum ever could. So the regulator is called LM338T. When you need a datasheet, you can usually just google the part number and hit the first PDF you see.
http://www.ti.com/lit/ds/symlink/lm138.pdf
The relevant equation is on page 7. What I have done on a build before is to solder in a pot or trimpot, find the voltage I want, then sub in the resistor of that value. To me this is better than putting a trimpot in the amp - trimpots get bumped, or you might forget what it does, etc. so to me a critical function like this, which does not need to be tweaked later on, is better as a fixed value.
Quote from: Taylor on April 18, 2012, 02:20:26 AM
Quote from: Ark Angel HFB on April 18, 2012, 12:24:59 AM
Ok so here are some things to consider / help me out with... 1 you might want to go ahead and give a heads up about the kit not including the 10k pot... just saying I was getting ready to build this it tonight then had to go aaa crap... I don't have a part. it isn't a big deal. they are $1 off ebay with free shipping so it is on it's way... but it was a bit of a disappointment to have to wait. XD
Hmm, ok, this is tricky because I do state precisely everything that comes in the kit, but not what doesn't come in the kit. The reason it doesn't come with the pot is that there a million different types and every person will want a different one (9mm for 1590a builds, 25mm for heavy duty amp guys/solid shaft, knurled shaft...). This is also why the kit doesn't come with an enclosure, knob, heat sinks, etc. But I definitely see how that could be confusing and a little annoying for somebody who doesn't know quite what they need. I will think about how to solve this.
Quote
I'm using a 15vDC 4A Power supply so...
A. what value should the 1k resistor change to to give me a steady 12.5vDC.
or
B. Simply tell me how to do the calculation and I will do it myself so it is not like I'm just asking for all the answers in the world. XD
No problem asking questions, however now is a good time to learn that about datasheets! :) Every part in the world has a datasheet, and it knows more about the part than even the legends on this forum ever could. So the regulator is called LM338T. When you need a datasheet, you can usually just google the part number and hit the first PDF you see.
http://www.ti.com/lit/ds/symlink/lm138.pdf
The relevant equation is on page 7. What I have done on a build before is to solder in a pot or trimpot, find the voltage I want, then sub in the resistor of that value. To me this is better than putting a trimpot in the amp - trimpots get bumped, or you might forget what it does, etc. so to me a critical function like this, which does not need to be tweaked later on, is better as a fixed value.
Thanks for the help... I completely get what you are saying and I wasn't saying that you should have included a pot... as like you said everyone has their own type of pots that they like... someone might want to get a push/pull and have it act as a switch. What I was suggesting was to find an place to state that a 10k pot is needed. it wouldn't hurt anything to treat it the was as your international shipping message.
heck you could probably even have a quick three line bit about were to buy the for cheap and what to look for. People find actions like this reassuring... although you time might be mostly wasted as most here know how to buy a pot and what to look for. ^_^
On a related side note I could have sworn I was very good at math... but now my brain hurts and I feel dizzy. T_T... how the hell do I find out Vout... do I just stick in the number I want it to be then solve for that number. T_T...
I can't find any female jacks for my 15v power supply. Can I just rewire the male from a 6mm to a 5.1 which are available locally. I guess I'm being impatient.
Look up a few posts, I had a similar question. The answer is yes, you can but then you run the risk of using your specialized power supply with a regular pedal, which could cause problems.
Built the Tiny Giant today and plugged it up and the TDA7240A melted. Any idea what is wrong. I ordered everything as a kit. I am using this power supply http://www.ebay.com/itm/270860174266 Thanks for the help
Did you do all of the stuff mentioned in the PDF to do before powering it up? Checking for continuity, etc.? Have you looked over your board for shorts across solder pads?
Yeah I checked everything. I will double check everything in the morning and go get a new tda7240. It is possible I overlooked something.
Hey All, I'm very interested in this little amp. For those who have built and used the amp for a while, what do you think? Does it sound good built stock plugging a guitar direct (or using foot pedals) and then direct to a speaker cab?
Even better, if you have some audio of the amp in use, that would be great. There is not much available on the internet. Thanks!
I think I need a new hobby. In my efforts to build the Tiny Giant, I have been practicing with some easier builds in order to boost confidence. Unfortunately, I have not been able to build anything that works at all. I don't know what it is, but I'm ready to quit. I'm so bad at this, I can't even get a smokey clone op amp to work. One chip and two caps with a couple jacks and a speaker. How flippin hard could it be. Needless to say I'm frustrated. Any tips or advice on how to get this right?
Travis
Quote from: zuk16l on April 25, 2012, 12:19:06 AM
I think I need a new hobby. In my efforts to build the Tiny Giant, I have been practicing with some easier builds in order to boost confidence. Unfortunately, I have not been able to build anything that works at all. I don't know what it is, but I'm ready to quit. I'm so bad at this, I can't even get a smokey clone op amp to work. One chip and two caps with a couple jacks and a speaker. How flippin hard could it be. Needless to say I'm frustrated. Any tips or advice on how to get this right?
Travis
First, I'd recommend starting new threads for builds other than the tiny giant, but, here is a good place to start:
http://www.diystompboxes.com/wiki/index.php?title=Debugging
When something doesn't work, probe through it, starting at the input with an audio probe. This is easiest with effects rather than amps of course. Post photos of your builds - maybe somebody will see something glaring that is causing you trouble. Perhaps your soldering technique needs some help.
QuoteFor those who have built and used the amp for a while, what do you think? Does it sound good built stock plugging a guitar direct (or using foot pedals) and then direct to a speaker cab?
yes! mine is going straight into a jensen mod 10" in a faux train case, works perfectly for rehearsals I have in a group with an upright, violin, accordion, and drum set (quietly played). I normally play out of a hotrod deluxe, but am too lazy to haul it to every bands' rehearsals I have. Built it a few months ago. I could post some examples in a week or so, but none right away, sorry.
QuoteI'm so bad at this, I can't even get a smokey clone op amp to work.
Ever watch a 3 year old try and write their name? Nothing is easy at first. We can get that smokey clone to work. My advice to you is to start a thread "Total noob can't make a smokey clone". Take pictures of what you have done. Look through the trouble shooting guide here (http://www.diystompboxes.com/smfforum/index.php?topic=29816.0). Do a lot of site:diystompboxes.com google searches, then ask every single question you might have. Give every shred of information about the components you're using. Once you get that to work, do the same thing for the next project. The Tiny Giant will be your friend after a build or two. You'll be making modular synths in a couple of years. Give or take. :icon_wink:
For the output jack, does it matter which wire connects where? From the schematic, it looks like it shouldn't but I'm trying to narrow down my possible mistakes.
Secondly, could powering it up without a load cause problems?
The speaker wires can go either way.
Powering it up without a load will not damage the amp, but of course it won't make any sound with no speaker connected. I'm sure you know that, just pointing it out for clarity's sake.
i was thinking of adding an mp3 input to this so i could play some music while playing the guitar. so do i just connect the mp3 input straight to the output of the opamp buffer, just before the power amp? or would i need a mixer?
thanks.. ;)
You would need a mixer. You can do a really simple resistive mixer, but these don't perform very well. You should be able to find a simple active mixer schematic on google.
so output of the mixer is connected directly to the input of the power amp? after the opamp buffer? ???
That's probably the best way, yes.
Just joined as I stumbled on this forum from the Tiny giant page. You folks sure are having fun! I looked through the posts and did not see this but has anyone created a "stereo" version - two TG's controlled by a double volume pot? I was thinking of this since I have both guitar and bass muti-effects pedals that output in stereo. A stereo 40w head for either bass or guitar with separated speaker cabs would sound cool for chorus/phase effects I bet.
You could run two TG's on one laptop PS right???
Thanks, Bob
Yes, a friend of mine has built one just like that. He runs it off of a single power supply and it works well.
is the buffer on the tiny giant suppose to make the guitar signal stronger?
i tried building the power amp section only without the buffer and the guitar signal is really weak as compared to my iPod signal. :-\
The input of the TG is a booster. It doesn't have a huge amount of gain, though. The output of an iPod is going to be way larger than that of a guitar. Did you build the mixer you were planning to do? Part of a mixer's job is to balance levels from disparate sources.
I haven't built the mixer yet. I just swap inputs to check which was louder and the guitar was really subtle.
Can I swap another booster of the TG something like AMZ mini booster? Or should I just retain the TG's booster and run AMZ booster before it as a pedal? I wonder which would sound better on clean signal. BTW, is 11.6V really necessary for the booster and the amp itself? I was using exactly 12V for the power amp section.
Thanks.
edit:
Found this on google. The right part looks like a buffer or a booster I think. If I use this on the TG, will I still need the TG's booster? Or should I just connect them all to get more gain perhaps?
I noticed, TG's input was fed on the + side of the opamp and in this mixer, it's fed on the - side. Is that good?
(http://www.generalguitargadgets.com/diagrams/mixer_sc.gif)
hey guys! great little build taylor and the quality of the board is top notch.
Ive completed the build but the amp seems to break up at around volume 3. Only way to describe it is a farty type sound and its effected by how hard/soft I play.
any ideas what could be wrong or is that the sound I should get?
What are you feeding into it?
I hit it with an ipod sometimes and can crank it up way past 3 without distortion. Could possibly be that the biasing on the input to the TL072 is dodgy (bad solder joints on the 10k resistors?) or that your voltages are not right. Can you post voltage readings for the ICs?
Finished up the offboard wiring last night and finally, after much fiddling cursing and dropping of screws, nuts and spacers managed to fire it up for the first time. Was in a bit of hurry as time was getting on so only managed to put it through my small 5w elac speaker but sounded pretty good (the speaker is in my 5w ax84 P1 amp, another thumbs up from a tube afficianado!). I hope to get it hooked up to a pair of 10 inchers in a 70w cab asap.
I'm using a scrounged PSU from a defunct laptop that gives 20v at 3.5A (Dell) so set it up using the 1.5K resistor on the regulator and got 16.69v on my meter. Two niggles when building, the ic socket had got it's legs mangled in the post, pity it wasn't stuck into the other side of the foam the tlo72 was in, and one of the screw and nuts wouldn't go together I figured a damaged thread: replaced both the socket and the screw/nut and had no further problems: except how small and fiddly it is to solder up ( hey I'm over 40 and my eyesight isn't what it was!
Plan now is to build a stompbox type preamp to run off the regulated 16.69v and put in the same case, any recommendations for one which will clean right up, but still get to a decent classic rock sound?
Oh yes, you can also chalk me up as one who'll have to file down the lip on the case lid to make sure it doesn't contact the ic tabs, doh!
Avulon.
Could you use the GGG charge pump to power the TG off a 9V wall wart? Obviously I still haven't built mine, other stuff came up... and I still can't get my gristleizer to 100% function :icon_cry:
No, the TG needs way more current than the charge pump can provide.
Quote from: Avulon on May 24, 2012, 08:40:01 AM
Plan now is to build a stompbox type preamp to run off the regulated 16.69v and put in the same case, any recommendations for one which will clean right up, but still get to a decent classic rock sound?
Mine sounds really good with a Colorsound Overdriver as a preamp, gets you everything from clean to a nice amp like bit of distortion.
Got it, thanks Slacker!
Quote from: Avulon on May 24, 2012, 08:40:01 AM
I'm using a scrounged PSU from a defunct laptop that gives 20v at 3.5A (Dell) so set it up using the 1.5K resistor on the regulator and got 16.69v on my meter. Two niggles when building, the ic socket had got it's legs mangled in the post, pity it wasn't stuck into the other side of the foam the tlo72 was in, and one of the screw and nuts wouldn't go together I figured a damaged thread: replaced both the socket and the screw/nut and had no further problems: except how small and fiddly it is to solder up ( hey I'm over 40 and my eyesight isn't what it was!
Hi Avulon, thanks for the feedback on the kit. Glad you're liking it!
I've now managed to test using a 4 ohm load (two paralleled celestion 10 inchers) and it still sounds good - until I hit max vol then it cut in and out before cutting out completly, rolling the volume back a hair and waiting a moment and the sound came back. I guess I pushed one of the chips into shutdown. My gut feeling is that it's the power chip as I'm running it at 16.69v, there was no discernible heat from either chip when it did this. I've still to put in a regulated voltage take off. when I do I'll push it into cut off and check what the voltage does, that should tell me whether it's the regulator or the amp chip. I'll also test with an 8ohm load (single speaker) and see if it still does it.
As far as a preamp, I took a look at the coloursound overdrive, which seems like a fuzz circuit, but am leaning more towards an English Channel or BSIAB, I'll try and get one on the breadboard to feed the amp and see how I like it.
The best power supply I could find was 19v and 4a. Would you guys think it's beneficial at all to use a voltage divider to bring it down to 16v (1v higher than the recommended 15v to leave some wiggleroom)?
I'm assuming if I were to, 1/4w would not be a sufficient size. Another consideration is the heat from these resistors offsetting the reduction in heat from the lm338, negating the idea of doing this in the first place.
Any thoughts?
Thanks,
Murad
QuoteThe best power supply I could find was 19v and 4a. Would you guys think it's beneficial at all to use a voltage divider to bring it down to 16v (1v higher than the recommended 15v to leave some wiggleroom)?
Nope. Just leave as is. As long as the LM338T is properly heatsinked (?), there isn't a need to use an additional voltage divider. It's also OK to change the resistor(s) that set the output voltage of the 338. The rest of the circuit will handle 16V, so you might as well run it at that voltage. (I wouldn't go any higher though).
Quote from: waltk on June 05, 2012, 09:42:43 AM
Nope. Just leave as is. As long as the LM338T is properly heatsinked (?), there isn't a need to use an additional voltage divider. It's also OK to change the resistor(s) that set the output voltage of the 338. The rest of the circuit will handle 16V, so you might as well run it at that voltage. (I wouldn't go any higher though).
Groovy, thank you! Much appreciated.
I play electric mandolin in a strange band that is occasionally mobile. The guitar, violin, accordion and myself play through smokey amps taped onto helmets with speakers bolted on top. Obviously, those little 386s are no match for trombones, trumpets and drums, and although I love the "tone" of the smokey, it'd also be nice to have something with higher fidelity than a speaker phone. The tiny giant would be perfect, but so far the best thing I can find is a pricey cordless drill battery, 18V @ 3 AH. Is that enough amperage for the Tiny Giant? When we're mobile, we usually play less than 30 minutes. Also, we don't have to be super loud, just audible. Any other ideas? Thanks dudes!
(http://farm4.staticflickr.com/3179/2954147886_699922e109_m.jpg)
That drill battery should work - WaltK has done exactly that with a similar amp design. I can't speak to the battery life (maybe he can weigh in) but if the batteries you're looking at are new, I bet you could get an old cordless drill for fairly cheap. The motors on the cheap ones wear out, probably a while before the battery's recharge lifespan is out, so people are often throwing them away anyway.
Cool photo! Would like to see you guys sometime. Sort of reminds me of a crazy DIY marching band I saw in San Francisco once.
QuoteThat drill battery should work - WaltK has done exactly that with a similar amp design.
Yea - works great. I use 18V lithium batteries (I think they're 3.0AH). They are very pricey, but since I already had some for my power tools, it was a low-cost proposition for me. Plays for hours.
Haven't tried this, but I think a 12-pack of (high-drain lithium rechargeable) AA batteries might also work. Most power tool power packs just contain sub-c size individual cells. The TG draws a bunch of current when you first turn it on, then settles down to a reasonable current draw, so I would expect you could easily play for 1/2 hour with a double-A pack - maybe even triple-As. Just wire e'em up in series (maybe with 3 standard 4-cell battery holders). In a pinch, you can then power the thing from disposable batteries too.
The speaker(s) you use makes a huge difference, and it's not easy to find efficient small speakers.
Echoing Walt:
> cordless drill battery, 18V @ 3 AH.
At HIGH volume in 4 ohms, most of an hour. Much longer at lazy level, but competing with brass I bet you'll have to slam it hard.
A 12V lead/acid alarm or motorcycle battery would work. Omit the TG's regulator, go right into the power amp chip. This does add danger of acid-burn, and may not be lighter, but is cheaper if you get lucky.
Speaker size and selection is VERY important. The 4-inch horns are a good deal for the mandolin, and the squeeze-box if it doesn't expect full bass. The 8-inch is a bit better. Either would be better with a cardboard extension to flare-out to a larger mouth. 250Hz needs at least 10 inch diameter mouth or sound waves don't happen. $1 of posterboard may be enough for two shows, affordable for an occasional gig.
I would not like full-bodied guitar through either speaker, but I admit that any "decent guitar speaker" will be too big and heavy to ride on your head for 30 minutes.
Quote from: Avulon on May 28, 2012, 02:29:08 AM
I've now managed to test using a 4 ohm load (two paralleled celestion 10 inchers) and it still sounds good - until I hit max vol then it cut in and out before cutting out completly, rolling the volume back a hair and waiting a moment and the sound came back. I guess I pushed one of the chips into shutdown. My gut feeling is that it's the power chip as I'm running it at 16.69v, there was no discernible heat from either chip when it did this. I've still to put in a regulated voltage take off. when I do I'll push it into cut off and check what the voltage does, that should tell me whether it's the regulator or the amp chip. I'll also test with an 8ohm load (single speaker) and see if it still does it.
Now tested into 8ohm load, this time it didn't cut out at full vol. When connected to the 4ohm load it also seems to depend on the input signal level, e.g rolling back the vol on the guitar also made it stop cutting out, which makes me more certain it's too much current in the amp chip (due to running at the higher 16.69 voltage). So at some point I'll have to replace the 1.5k on the voltage regulator with a 1.2 to lower the voltage a little.
I've now also heard the Catalinbread RAH pedal and am set on building this for the pre-amp - parts collection has already started - maybe I'll need a bigger box! medium sized giant anyone? :)
Avulon
P.S it seems almost as loud into 8ohm as 4ohm - but only tested in my workshop which isn't that big a space.
Thanks for the replies y'all! I can't wait to try those ideas out.
PRR, I am a little scared of the acid burn, I guess just cause it sounds really scary. Also, when we play, we move around a lot, so weight is an issue. But we do have a couple motorcycle geeks in the band, I'll talk with them. Great suggestion!
I plugged a few gigs I have next weekend on this wax cylinder post (http://www.diystompboxes.com/smfforum/index.php?topic=97792.0) in the Lounge if you're interested and available. Can't wait to have a Tiny Giant on my head!
Quote from: Avulon on June 08, 2012, 08:30:14 AM
P.S it seems almost as loud into 8ohm as 4ohm - but only tested in my workshop which isn't that big a space.
Sounds about right. Most amps will put out less than double the power into half the load, and double the power is approximately the threshold of an audible change in volume. Speaker sensitivity is a more important factor if you're trying to get as much volume as possible out of it, as well as EQ.
Ok, so i'm new in this forum but i have built the tiny giant a couple of months ago and it's still working perfectly (awesome little amp by the way, Taylor!), but from the beginning i don't know why, i feel that it is missing some highs, maybe because i mounted it in a home made pine cab with a 10'' 4ohm speaker (jensen mod10-35)?
if i change the cap to the volume pot maybe i can get more treble? i don't want to put another pot for the tone, cause i'm planning to add a professor tweed as a pre amp and power it with the regulated 11.6V from the TG, and it has already a tone pot, but i think that if i leave the TG as it is, i will still have problems with the high frequencies not passing through...
PS: sorry for comming only now into this discussion, cause i've been reading this entire thread and others also and learned a lot in the process, so thanks to everyone who's posting their knowledge and experiences in this forum, and major thanks to taylor for this cool project!
SeeYa
Parra
> problems with the high frequencies not passing through...
The TG passes highs just fine.
Changing the cap to the volume pot won't get more treble. (It affects bass-drop, but you don't want to cut bass SO much that only the highs are left.)
However: The TG is a "flat" amp, what you put in is what you get out. Most guitar amps have some or a lot of Treble Boost. So compared to some "typical guitar amp", the TG may be less bright. TG=vanilla, 5F6a=salsa.
There's many thing you can put in front for tone-shaping.
Hi, I've already successfully built one of the tiny giants and recently finished my second. This time I wanted to add a switch volume pot and led. I've gotten the led to light up and turn off when the switch is switched however there's no sound at all. At first I had the power wired wrong but fixed that. Any tips?
thanks for the reply PRR
> problems with the high frequencies not passing through...
yeah, i didn't explain myself there right, it's true, the TG really gives what you send to it, i just wanna get a bit more treble without changing the TG circuit with tone stacks and eq, so i was thinking if i add a preamp circuit this will fix my problem or not?
By the way i'm not sure if i should try the ROG professor tweed (and power it from the 12von the TG) or the ROG supreaux deux and if this one can be powered by the 18 v from the laptop power supply or if i need some sort of regulator, or to the 12 v with a charge pump. what do you think? (to many questions i know sorry! =])
PS: when i get the camera i'll take some photos.
Quote from: trem7 on June 09, 2012, 11:53:00 AM
Hi, I've already successfully built one of the tiny giants and recently finished my second. This time I wanted to add a switch volume pot and led. I've gotten the led to light up and turn off when the switch is switched however there's no sound at all. At first I had the power wired wrong but fixed that. Any tips?
What do you want your switch to do? Standby or power? Was the amp working before you added the switch? How did you wire the switch?
Quote from: parra on June 09, 2012, 02:28:45 PM
yeah, i didn't explain myself there right, it's true, the TG really gives what you send to it, i just wanna get a bit more treble without changing the TG circuit with tone stacks and eq, so i was thinking if i add a preamp circuit this will fix my problem or not?
The traditional guitarist solution is a treble booster like a Rangemaster. There should be more treble booster circuits than you could ever dream of if you search this forum. I'm not a guitarist so I can't recommend a good one - I'd probably pick the simplest one-transistor silicon one I found.
Runoffgroove.com (http://www.runoffgroove.com/articles.html) is a great place to look for what you're asking. Their English Channel (http://www.runoffgroove.com/englishchannel.html) project might be what you're looking for.
I want the switch to be power, I have the switch wired between the positive on the dc jack and the board. I'll try taking the switch out and see if it works.
Built my first TG. It's great!
Like many others, I plan on creating a preamp with some ROG designs. I'm going to try the Professor Tweed tonight, but thought about adjusting the negative feedback arrangement.
On the actual Princeton Amp, the negative feedback is tapped off the speaker, and feeds back into the cathode. In the Professor tweed, it feeds off the FET that simulates the 6v6, and goes to the last preamp stage's emitter.
Would I be safe in tapping the feedback off the speaker output from the tiny giant? I know this is something I can simply test after making sure the pedal works stock, but I want to make sure I want harm any components with this idea since it probably hasn't been done before. Would I need to do away with the 1uf feedback cap? Or would DC muck everything up?
Thanks again guys.
I'm hoping PRR or RG (or somebody else who knows way more than I do) will weigh in on that, but what exactly are you hoping to achieve with that?
I should also say that, until somebody who knows tells you that you should do that, I would recommend that you don't.
So I've gotten the amp to work, I removed the LED and resistor which was before the switch. There's a pop when switching on and off so I will be adding a standby switch. In which part of the circuit should I wire the LED?
The LED should be wired in parallel to the circuit, that is, it's not part of the circuit. It will turn off when you switch the power off, it will turn on when you switch the power on, regardless of what the Tiny Giant does.
Positive voltage -> power switch -> 1-2K resistor -> LED anode (+, the longer leg) -> LED cathode (-, the shorter leg) -> ground.
see here (http://www.beavisaudio.com/techpages/StompboxWiring/) if you're confused
Quote from: Taylor on June 11, 2012, 06:28:59 PM
I'm hoping PRR or RG (or somebody else who knows way more than I do) will weigh in on that, but what exactly are you hoping to achieve with that?
I should also say that, until somebody who knows tells you that you should do that, I would recommend that you don't.
Hoping to use the TG as a poweramp for some FET preamps to sound relatively close to the tube amps these preamps emulate. I understand that the Professor Tweed uses the negative feedback from the section that simulates the poweramp, but it actually comes from the speaker tap in the real thing. The ideal goal is to get a closer simulation to the real thing, and I'm hoping that the possible increase in bandwidth from the global negative feedback will help. I know you'll say that the TG is already a very flat amp, but this could potentially be very helpful for the voicing of the preamp as well, since we'll be feeding the signal back the last or second to last stage. There will be a sacrifice in output gain, but the TG has lots to spare.
Also, this opens us up to the use of the more feel based amp power controls, like Presence, Depth, and Speaker Damping. This could really be great for guys who want to build a great sounding SS amp that emulates it's bigger tube based brothers.
I'm really inspired by the possibilities of a tiny loud and clean amplifier. So I think I'm doing it justice by pushing the possibilities as far as imagination will let it run.
Thanks again for all the awesome designs.
Thanks for the help guys. Still pretty new to DIY electronics. So the switch I have is a pot with a switch. Can I make this work or will I need a different switch?
If you're up for spending a buck or two and have the patience or time to order the part, I suggest this type of switch, with built-in LED:
(https://encrypted-tbn3.google.com/images?q=tbn:ANd9GcTneOxiNF_Mop85K4pTfXtiFgNBkhv17I_8WGm5zvYzPxUAWa8h)
> Would I be safe in tapping the feedback off the speaker output from the tiny giant?
No.
> I know this is something I can simply test after making sure the pedal works stock
There is much risk for burning-up the power chip. While TDA7240 is pretty bullet-proof against load mis-connections, wrapping feedback around that many stages is pretty sure to oscillate, probably hypersonically, which gets all the internal power transistors VERY hot in a way that the internal protection systems are not designed to handle.
The TDA7240 _has_ NFB, internally, for the same reason the Princeton takes NFB from output to driver. This means the TDA7240 _controls_ the speaker, no deviation.... it does what the Prof Tweed tells it to do.
BTW, the TG has _two_ speaker outputs. Unlike Princeton, neither side is grounded.
Quote from: PRR on June 13, 2012, 09:47:10 PM
> Would I be safe in tapping the feedback off the speaker output from the tiny giant?
No.
> I know this is something I can simply test after making sure the pedal works stock
There is much risk for burning-up the power chip. While TDA7240 is pretty bullet-proof against load mis-connections, wrapping feedback around that many stages is pretty sure to oscillate, probably hypersonically, which gets all the internal power transistors VERY hot in a way that the internal protection systems are not designed to handle.
The TDA7240 _has_ NFB, internally, for the same reason the Princeton takes NFB from output to driver. This means the TDA7240 _controls_ the speaker, no deviation.... it does what the Prof Tweed tells it to do.
BTW, the TG has _two_ speaker outputs. Unlike Princeton, neither side is grounded.
Makes sense! I guess I can mess around with the feedback in other stages of the pedal feeding the TG. Thank you for the heads up!
On a separate note. I've been noticing the common complain that the TG is lacking in the high end department. I understand it's because we're used to most guitar amps having that high frequency boost, but it does affect how ROG pedals sound as preamps. Has anyone modified the TG's opamp section to have a high end boost? I was thinking decreasing the cap size and increasing the feedback resistor. This would hopefully keep the lows/mids at the same volume and only boost the highs if my understanding of non inverting HPF's is sound. Any thoughts?
Sorry for replying again (couldn't find edit button for some reason).
But I just wanted to add that I did build it, and I found myself missing that high end available in typical guitar amps.
My goal is the have the TG resemble a typical guitar power amp as much as possible, to utilize ROG and ROG-esque tube-to-fet pedals as preamps. I will modify the preamps as necessary. I'd ideally like to avoid adding the high end in the pedals, so I'm thinking adding the "sparkle" to the poweramp section would be the way to go.
Any suggestions besides modding the input opamp section of the TG (which I'm going to experiment with this week)?
Thanks guys.
> complain that the TG is lacking in the high end
I think many people overlook or mis-read these good words in the manual:
"It's designed to be a clean full-range amp without any inherent EQ curve or distortion. This allows you to pair it up with your favorite effects, preamps, and/or equalizers to build your own custom amp."
Here's a simple high-boost (added R and C) plus alternate bass cutoff "try" cap values (the very extended bass "may" overwhelm treble).
(http://i.imgur.com/bNpK1.gif)
> couldn't find edit button
On this forum: "edit" goes away in a day. You can edit your post for about 24 hours, then it is locked to reduce time-warp confusion. I know other forums with perpetual re-editing, rarely someone will abuse that. Very reasonable, but a bit confusing if you have quick-edited here then find a reason to re-edit a day or more later.
Quote from: garcho on June 11, 2012, 07:23:38 PM
The LED should be wired in parallel to the circuit, that is, it's not part of the circuit. It will turn off when you switch the power off, it will turn on when you switch the power on, regardless of what the Tiny Giant does.
Positive voltage -> power switch -> 1-2K resistor -> LED anode (+, the longer leg) -> LED cathode (-, the shorter leg) -> ground.
see here (http://www.beavisaudio.com/techpages/StompboxWiring/) if you're confused
I don't think that the wiring scheme you refernced will work for the TG. The chip that the TG uses has a standby switch connected across a capacitor that is connected to pin 2 on the chip and not a traditional power switch like most of our stomp boxes. There is no main power switch where you could place an LED in parallel. You also have to be aware that the output (speaker) has to be connected to the chip and not to ground. Here's the schematic:
(http://i1160.photobucket.com/albums/q485/jdansti/3afed537.jpg)
One option might be to jumper across the standby switch connection on the PCB so that the "switch" is permanently closed and then add a DPDT switch to the output of the power supply. You could add the LED and limiting resistor to the new DPDT switch.
Quote from: PRR on June 17, 2012, 01:23:49 AM
I think many people overlook or mis-read these good words in the manual:
"It's designed to be a clean full-range amp without any inherent EQ curve or distortion. This allows you to pair it up with your favorite effects, preamps, and/or equalizers to build your own custom amp."
Here's a simple high-boost (added R and C) plus alternate bass cutoff "try" cap values (the very extended bass "may" overwhelm treble).
Absolutely. Didn't miss that section at all. I'd just never built anything completely "flat" before, so I'd never had a point of reference for what flat really sounds like in terms of guitar tone. So believe me, I'm not whining about the TG at all. I just want to make it closer to a typical guitar power amp. I will definitely experiment with the EQ changes you've suggested, and other options I've come across as well.
Thank you again.
Quote
On this forum: "edit" goes away in a day. You can edit your post for about 24 hours, then it is locked to reduce time-warp confusion. I know other forums with perpetual re-editing, rarely someone will abuse that. Very reasonable, but a bit confusing if you have quick-edited here then find a reason to re-edit a day or more later.
Makes sense. I figured that was the case. Thanks for clarifying.
I just finished building my first TGA, and it works, kinda. Only problem is that the volume is incredibly low (whisper-like). Does anybody have any idea where I went wrong? I can post pictures or anything if needed. Did all the checks in the PDF. Thanks in advance!
Does the volume level change at all when you turn the volume pot?
A picture might help.
Quote from: waltk on July 05, 2012, 07:59:06 PM
Does the volume level change at all when you turn the volume pot?
A picture might help.
The volume is only whisper-like at max-volume. Anything below that and it's inaudible.
I just found out that my camera can't really do macro pictures, so the ones up close are a bit out of focus. I hope they help. You can see there is a second pot, next to the volume, that isn't connected. This will be the tone knob, but first I want to get it to work without it. It has an internat speaker, 4 ohm, and a jack for external speaker next to the power jack. It has a switch for standby and led, and a switch for internal/external speaker. I really have no idea what I did wrong...
Oh, and the heatsink is normally attached to the bottom plate, so it isn't just dangling around in there, as it looks like now.
(http://i.imgur.com/k41Dw.jpg)
(http://i.imgur.com/sBetG.jpg)
(http://i.imgur.com/sTdCY.jpg)
(http://i.imgur.com/BVzPO.jpg)
It's too bad your camera doesn't have macro focus - very difficult to see anything clearly in the photos.
It looks like your volume pot might be mis-wired. On the PCB, the pads for the pot numbered 1-2-3 are connected to the yellow-red-orange wires. It looks like the red and orange wires are connected to the pot on terminals 1 and 2 (can't tell which is which from the photo). The yellow wire should be on pin 1 (top terminal in the photo).
It's hard tell how things are connected from the photos. As a general debugging technique, you should probably use your meter to check continuity for all the off-board wiring. Is there continuity everywhere there is supposed to be? Is there isolation everywhere else? For example, with your standby switch off, make sure there is no continuity between the standby pads on the PCB. With your speaker switch set to "internal" make sure the speaker pad on the PCB have continuity with the terminals on the speaker. Make sure the speaker actually has some resistance between the terminal (about 3.2 ohms of DC resistance).
-Walt
Quote from: waltk on July 06, 2012, 11:06:56 AM
It's too bad your camera doesn't have macro focus - very difficult to see anything clearly in the photos.
Dear Walt, thank you for your reply. Here are some better pictures I just took. The back of the board looks a bit dirty from the resin in my solder. BTW, I use a 15v 4.5a laptop power supply.
(http://i.imgur.com/nMPrg.jpg)
(http://i.imgur.com/ioo4H.jpg)
Quote from: waltk on July 06, 2012, 11:06:56 AM
It looks like your volume pot might be mis-wired. On the PCB, the pads for the pot numbered 1-2-3 are connected to the yellow-red-orange wires. It looks like the red and orange wires are connected to the pot on terminals 1 and 2 (can't tell which is which from the photo). The yellow wire should be on pin 1 (top terminal in the photo).
I know, but it's just wired in reverse, so that can't be the cause of this problem.
Quote from: waltk on July 06, 2012, 11:06:56 AM
It's hard tell how things are connected from the photos. As a general debugging technique, you should probably use your meter to check continuity for all the off-board wiring. Is there continuity everywhere there is supposed to be? Is there isolation everywhere else? For example, with your standby switch off, make sure there is no continuity between the standby pads on the PCB. With your speaker switch set to "internal" make sure the speaker pad on the PCB have continuity with the terminals on the speaker. Make sure the speaker actually has some resistance between the terminal (about 3.2 ohms of DC resistance).
I did that before posting the problem here. Speaker measures 3.9 ohm. everything offboard seems to be isolated or continuous as it should be. Could it be that the problem is on the board? Is it my soldering, or can one of the components be broken?
update: I just did some more probing. The heatsinks of the LM338T and the TL072 are well isolated from eachother. However, there does seem to be continuity through the pcb. They read about 600 ohm apart. The heatsink of the TL072 alone reads continuity to ground, and the heatsink of the LM338T reads about 600 ohm to ground. Is this normal?
The heat sink = Vout. The resistance between the HS and ground should be the same as Vout to ground. You should have close to 0 ohms between the HS and Vout.
(http://i1160.photobucket.com/albums/q485/jdansti/447c915e.jpg)
I'd use some isopropyl (rubbing) alcohol and a tooth brush or nylon bristle brush to clean the back of the PCB. You really can't see solder bridges with all of that flux on there.
Quote from: Jdansti on July 06, 2012, 08:07:22 PM
The heat sink = Vout. The resistance between the HS and ground should be the same as Vout to ground. You should have close to 0 ohms between the HS and Vout.
Resistance from heat sink to Vout = 0 ohms. From sink to Vin about 1k and from sink to ADJ about 100 ohms. That's normal, right?
Quote from: Jdansti on July 06, 2012, 08:07:22 PM
I'd use some isopropyl (rubbing) alcohol and a tooth brush or nylon bristle brush to clean the back of the PCB. You really can't see solder bridges with all of that flux on there.
I cleaned the back, and can't find any bridges. Even resoldered some joints that might have been cold, but no change. I'm starting to doubt that I put on all the components correctly, going to check that now. What else can I do? Can I measure voltages at certain points or something?
Has anyone had this problem before (ultra low volume, but a working amp)?
QuoteIt looks like your volume pot might be mis-wired. On the PCB, the pads for the pot numbered 1-2-3 are connected to the yellow-red-orange wires. It looks like the red and orange wires are connected to the pot on terminals 1 and 2 (can't tell which is which from the photo). The yellow wire should be on pin 1 (top terminal in the photo).
QuoteI know, but it's just wired in reverse, so that can't be the cause of this problem.
Correct, the volume pot will just work backwards until you rewire it.
Quoteupdate: I just did some more probing. The heatsinks of the LM338T and the TL072 are well isolated from each other. However, there does seem to be continuity through the pcb. They read about 600 ohm apart. The heatsink of the TL072 alone reads continuity to ground, and the heatsink of the LM338T reads about 600 ohm to ground. Is this normal?
Assuming your reference to "TL072" was just a typo, and you really meant "TDA7240"... The heatsink for the LM338 is internally connected to Vout, so there should be zero resistance between the heatsink and Vout. The resistance between Vout (or heatsink) and ground should be the series resistance of the 1k and 120R resistors that set the voltage output - ~1,120 ohms. Because the TDA720 heatsink is internally connected to ground, the resistance between them should also be ~1,120 ohms. 600 is too low, and means there is a short somewhere.
The gain of the TL072 is fixed by the ratio of the 220k and 100k resistors next to it. The gain should be 3.2 (220k/100k + 1). You have used a 1M resistor in place of the 220k resistor. If your intent was to build a stock Tiny Giant, that's a mistake - but it doesn't explain why you have LESS volume. Based on the resistors you actually have in the circuit, the gain of the input stage would be 11 (1M/100k + 1). That is probably too much, and would cause clipping in the TDA7240 (which is not pretty).
At this point, you should probably try to figure out why there's only 600 ohms between the heatsink on the LM338 and ground. You should probably do this without power applied as much as possible (to avoid risk of frying components).
You should have high resistance between pin 3 (input) on the TL072 and ground (like 3Mohm). If you don't have a high resistance there, then your signal is being grounded somewhere before it gets to the opamp.
If you've corrected any faults that can be found without power applied, then try applying power again, and verify that pin 6 of the TDA7240 is getting power (about 11.6V).
Also, an audio probe might help determine where your signal is leaking off before it gets to the TDA7240.
+1 on the idea to scrub the solder side of the PCB with alcohol and a brush. It looks like there's not only rosin there, but a million flecks stray solder (maybe that's just an artifact of the photography though).
Good luck, let us know how it's going.
Dear Walt, thanks again for your help.
Quote from: waltk on July 07, 2012, 01:08:10 PM
QuoteIt looks like your volume pot might be mis-wired. On the PCB, the pads for the pot numbered 1-2-3 are connected to the yellow-red-orange wires. It looks like the red and orange wires are connected to the pot on terminals 1 and 2 (can't tell which is which from the photo). The yellow wire should be on pin 1 (top terminal in the photo).
QuoteI know, but it's just wired in reverse, so that can't be the cause of this problem.
Correct, the volume pot will just work backwards until you rewire it.
Just rewired this.
Quote from: waltk on July 07, 2012, 01:08:10 PM
Quoteupdate: I just did some more probing. The heatsinks of the LM338T and the TL072 are well isolated from each other. However, there does seem to be continuity through the pcb. They read about 600 ohm apart. The heatsink of the TL072 alone reads continuity to ground, and the heatsink of the LM338T reads about 600 ohm to ground. Is this normal?
Assuming your reference to "TL072" was just a typo, and you really meant "TDA7240"... The heatsink for the LM338 is internally connected to Vout, so there should be zero resistance between the heatsink and Vout. The resistance between Vout (or heatsink) and ground should be the series resistance of the 1k and 120R resistors that set the voltage output - ~1,120 ohms. Because the TDA720 heatsink is internally connected to ground, the resistance between them should also be ~1,120 ohms. 600 is too low, and means there is a short somewhere.
Yeah, sorry. I'm getting my parts numbers mixed up. To be clear: The resistance of the heatsink to ground in the LM338 = 1.12K. Heatsink to heatsink = 600 ohm.
Quote
The gain of the TL072 is fixed by the ratio of the 220k and 100k resistors next to it. The gain should be 3.2 (220k/100k + 1). You have used a 1M resistor in place of the 220k resistor. If your intent was to build a stock Tiny Giant, that's a mistake - but it doesn't explain why you have LESS volume. Based on the resistors you actually have in the circuit, the gain of the input stage would be 11 (1M/100k + 1). That is probably too much, and would cause clipping in the TDA7240 (which is not pretty).
I see, don't know how that happened. Fixing it now.
Quote
At this point, you should probably try to figure out why there's only 600 ohms between the heatsink on the LM338 and ground. You should probably do this without power applied as much as possible (to avoid risk of frying components).
You should have high resistance between pin 3 (input) on the TL072 and ground (like 3Mohm). If you don't have a high resistance there, then your signal is being grounded somewhere before it gets to the opamp.
Resistance between pin 3 and ground is only 175K. Does that narrow down my search area?
Quote
If you've corrected any faults that can be found without power applied, then try applying power again, and verify that pin 6 of the TDA7240 is getting power (about 11.6V).
Also, an audio probe might help determine where your signal is leaking off before it gets to the TDA7240.
+1 on the idea to scrub the solder side of the PCB with alcohol and a brush. It looks like there's not only rosin there, but a million flecks stray solder (maybe that's just an artifact of the photography though).
That was just some glare from the camera, no real flecks. Just a lot of resin. I don't have an audio probe, but I should get one (I normally build guitars, lap steels and such, only did 3 BYOC builds before this, all went smoothly).
Quote
Good luck, let us know how it's going.
Thanks, will do.
QuoteThe resistance of the heatsink to ground in the LM338 = 1.12K. Heatsink to heatsink = 600 ohm.
There's something really fishy about this. The heatsink of the TDA7240 is internally connected to ground - so there should be zero resistance between the TDA7240 heatsink, pin 4 on the TDA7240 (ground), and any other ground point on the PCB.
In other words, heatsink on the LM338 to ground should give the same result as heatsink (lm338) to heatsink (TDA7240).
Maybe it's just my BSE (bovine spongiform encephalopathy) acting up, but I can't think of how you could get this result.
Quote from: waltk on July 07, 2012, 03:17:27 PM
QuoteThe resistance of the heatsink to ground in the LM338 = 1.12K. Heatsink to heatsink = 600 ohm.
There's something really fishy about this. The heatsink of the TDA7240 is internally connected to ground - so there should be zero resistance between the TDA7240 heatsink, pin 4 on the TDA7240 (ground), and any other ground point on the PCB.
In other words, heatsink on the LM338 to ground should give the same result as heatsink (lm338) to heatsink (TDA7240).
Maybe it's just my BSE (bovine spongiform encephalopathy) acting up, but I can't think of how you could get this result.
I've checked the schematic, and I agree, it makes no sense at all. I've checked all my joints, all looks fine. There's good isolation between the big heat sink and the parts.
Also, I just switched the 1meg resistor for a 220K, and now it does nothing at all. The PCB doesn't seem to like all my probing and resoldering, it's starting to crumble at places. I'm about to just give up and go back to building guitars.
QuoteI'm about to just give up and go back to building guitars.
Yeah, it's frustrating - but don't give up yet. This little amp sounds great when it's done, and you're almost there.
QuoteAlso, I just switched the 1meg resistor for a 220K, and now it does nothing at all.
Ok. So switching that resistor has set the input gain where it should be. It's not surprising that your output was reduced from a whisper to an inaudible whisper. The good news it that even though your output was a whisper (before correcting the gain), there was some signal making it all the way through to your speaker.
The other good news is that all your other components appear to be in the right places.
Is it possible that there's a short in the standby circuit? (in the switch or a solder bridge on the board)
Well, I just discovered one silly mistake. I wired the LED so that it would switch on when the standby-leads would connect. So when the amp would switch to standby.
This still does not explain my problem: The amp produced whisper-like volumes while standby, and it does not work now when the leads are disconnected.
Quote from: waltk on July 07, 2012, 09:06:32 PM
Yeah, it's frustrating - but don't give up yet. This little amp sounds great when it's done, and you're almost there.
Not giving up yet, thanks again for the help.
Quote
Is it possible that there's a short in the standby circuit? (in the switch or a solder bridge on the board)
While disconnected, the standby leads have 5.2k resistance one way, and 4.7 the other way. Can this come from the 22uf cap?
QuoteWhile disconnected, the standby leads have 5.2k resistance one way, and 4.7 the other way. Can this come from the 22uf cap?
Nope, that doesn't sound right. The resistance can't come from the 22uF cap (unless it's internally shorted). What you're seeing is the internal resistance between pins 2 (standby) and 4 (ground) on the TDA7240. The reason I say it doesn't sound right is that I measured a few chips, both in a working TG and just pins 2 and 4 on the naked chip. All the chips I measured had between 55 and 60K ohms resistance. I'm starting to think your TDA7240 chip is bad. Try removing the 22uF cap connected to pin 2 (it's the one closest to the edge of the board), then measure the resistance between the standby leads again.
If the resistance is about 55-60K, then the 22uF cap is bad.
If the resistance is still about 5k, then the TDA7240 is likely bad.
The only other thing it could be is if there's a partial short to ground from the pin 2 trace on the board (and I don't really see any place that would be likely).
I suggested removing the 22uF cap because that's easier than removing the 7-pin TDA7240 - but if you determine that it IS bad, then you might as well take it out (and verify the suspiciously low resistance between pins 2 and 4).
Good luck - keep after it.
-Walt
Quote
If the resistance is about 55-60K, then the 22uF cap is bad.
The cap was fine, so I removed the TDA7240. This was a real PITA, practically destroyed the PCB and the TDA7240 in the process (eyelets started coming loose, legs falling out). If the TDA wasn't broken before, it was now.
Quote
If the resistance is still about 5k, then the TDA7240 is likely bad.
luckily, the 2 and 4 pins were unharmed, so could be measured. And there it is: 6k resistance. So, problem found. However, there is a Dutch saying that roughly translates "operation a success, patient deceased". I hope that's not the case. I checked local electronics stores, and they don't sell the TDA7240. Even if I get a hold of one, will the PCB still work with the eyelets fallen out and all?
Quotepractically destroyed the PCB and the TDA7240 in the process (eyelets started coming loose, legs falling out). If the TDA wasn't broken before, it was now
Yes, desoldering a two-sided PCB with through-plated pads is a real PITA. In this case, it might be possible to salvage. The TDA7240 trace connections are all on the top (silk-screened) side of the board - except for pin 4 (ground) which is on the bottom. You would have to be sure that all the traces on the top-side has a solid connection. After all your trouble with it, though, it might be best to start over.
The TDA7240 IS hard to find. Maybe Taylor has some suggestions. (Taylor, are you there? ...)
Sorry guys, have not been able to check the forums as regularly lately. Lieuwe, if you contact me at the Music PCB site, I will set you up.
Hi !
[! approximated english content !]
I just finished to solder the tga. It works near well. It seems the tda is prone to oscillation at near full volume. Without boxe, moving cables solve the problem. Happilly, stable in some position. Funny horrible sound when it oscillate, it is the first time i ear such a thing, and is very distinctive. It's the only bad point, it don't seems to be really stable. All is like the schematic, i don't have a oscilloscope...any idea to investigate more on this problem? Both tda & lm seems to get be really hot too. It runs at 11,60v, but didn't verified @ how much current. My speaker is a eminence governor 16 ohm.I'll try to see if current seems normal.
Thinking.... => Should it came from bad symetry of the two RC networks from tda to the speaker if values of resistors/capacitors are not the same...? Don't this network should be ajusted for speaker impedance, like zobels networks in other amps ?
As it happen near full volume and as where the volume controle is located , i say it's the tda...but maybe the lm...don't know how to resolve it problem/optimize my circuit to get it better stabilised.
As it didn't affect oscillation problem, I've added big tank caps before (3*2200) and after (2*4700) the regulator, with protective diodes as show in the lm datasheet. I've replaced the tl074 by a tle2072. Didn't tryed yet really at full volume playing because the only cab i have here now has a eminence 12" governor wich is really too much efficient (around 101db spl in cab).
The tga will be part of a bigger project. I've already posted about it, and it still evoluate.
At home, the governor use to be driven by a lm386 based amp wich is enough and never run at full volume...and the lm386 is only near 0,5 watt ;).
I'll build a little tube ecl82(=6bm8=6f3p) amp (<2w) for this speaker to replace the lm386. I want to mix the tube amp with a mini sub with a active crossover for bass, i'll use the tga as a subwoofer amplifier. For sub, i'll do a 4 ohm 6,5" tapped horn only 88db spl, but from 30 to 100hz in only 15 liters (with good group delay) with a 18sound 6nd430 (because high BL,low distortion and more H2 than H3, and dynamic lows to cross with the eminence). I've calculated i'll need 18 time the power to get the same sound level between the sub and the guitar speaker. (101-88=13db difference => (13db/3)^2=18 time more power needed). So 0,5watt i like at home for guitar cab => 0,5*18=9 watt for my relativly low efficience sub project. The tga will do the trick with not a lot of distortion :)
As i got a 16v 4,5A laptop psu, it should be enough to power both amp, and other effects. (i'll have to do a efficient boost converter, i'd like to try with a Ti tpa40210+ voltage doubler maybe to do something different from the ne555 and max1771)
Thanks Taylor for this funny tiny Giant project :)
Cute pcb !
> prone to oscillation at near full volume. Without boxe, moving cables solve the problem.
All high-gain audio amplifiers WILL oscillate if input and output wires criss-cross and there is no box. Use a box.
> Both tda & lm seems to get be really hot too
If no box, what are you using for a heat-sink?
Hi!
I ordered the Tinygiant and are doing some planning, I would appreciate some advice
1. I have a 18.5 V / 3.5 A PC charger, wll it do? Does the higher voltage ease the 4A requirement?
2. I'm thinking of putting inside a small speaker cabinet (A TinyGiant combo :) ), about 8 liters. The Tinygiant will be in a aluminum enclusure, inside the speaker, but with a cutout in the back, also with a heatsink at the back. The speaker will have bass ports (adding some ventialtion?). Will there be heating problems?
Thanks in advance,
Jakob
QuoteI have a 18.5 V / 3.5 A PC charger, wll it do?
Yes, that will be fine.
QuoteDoes the higher voltage ease the 4A requirement?
The 4A "requirement" is really a conservative suggestion. You'll be fine with the 3.5A PS. Having a higher-voltage PS, however, doesn't change the current required for the chip. In fact, any excess input power has to be dissipated by the LM338. For example, suppose the chip is drawing .3A at 11.6V - the voltage regulator has to dissipate 2.07 watts ( (18.5-11.6) * .3) as heat. So a higher input voltage means that more heat will be generated in the LM338.
QuoteWill there be heating problems?
Probably not - sounds like a nice design. Having decent heat sinks on the chips will be sufficient. Just be careful to pay attention to the instructions about what can/can't be grounded. The heatsink on the TDA7240 CAN be grounded (it's internally connected to ground); the heatsink on the LM338 CAN'T be grounded (it's internally connected to the +11.6V output of the chip).
Have fun, and good luck with your build.
Hi,
Thanks Walt for your reply.
I'll post some pictures when it's ready, but it's my autumn/winter project so it'll take a few months time...
I'll be back...
/Jakob
Ok guys, I'm kind of trying to marry the Tiny Giant power amp section with Marshall Lead 12 preamp section.
Here's what I've drawn:
http://www.mediafire.com/?4mfhuppg3wlo6xn
I'm, of course, very unsure of this design. Would you guys mind seeing it?
[EDIT]
S...t, forgot to mention I replaced the stock tone stack with a Fender type 2-knob tone stack.
Here's the original Lead 12 schematic:
http://music-electronics-forum.com/attachments/2552d1212538675-3005.gif
And the tone stack I used:
http://amps.zugster.net/images/articles/tonestacks/6G5.gif
Hi,
I'm thinking of adding a few features to my TinyGiant. My idea is to build a small combo with 6,5" speaker to be used when traveling. But I still would like the option of headphones, line in and also 12V (car/boat battery) power.
I would appreciate any comments or acknowledgment on below thinking
Headphones
Should be straight forward as suggested in reply 218:
http://music-electronics-forum.com/attachments/3932d1230346488-squier15.gif
I believe there are headphones outlets that has the possibility to disconnect the speaker.
12V
A car/boat battery is providing around 12V: can I connect it skipping the power regulator?
If the car/boat's engine is running the generator will raise the voltage up to 14,5 V, can it be directly connected after power regulator still?
Or should I in both cases connect it to the power regulator?
Line in
This was suggested in reply 119: http://i.imgur.com/Uill1.gif
Someone tried it but got a lot of noise. I'm thinking of connecting an MP3, Ipod or similar.
Is it a good solution? Alternative?
Tone stack
As suggested I'll use the tone stack, should not be a problem I think...
Many thanks for any reply on this.
Regards,
Jakob
> voltage up to 14,5 V
The chip is MADE for use in cars roaring down the road.
Don't try this on a 1971 BSA motocycle after the dynamo diode falls off: that gives 15V at idle going 20V on the road. Also burns out all the bike's lamps in a few minutes, then the battery boils. (Actually, some car-sound chips will take 24V double-jump-starts; they shut-down at 18V and are OK for some minutes at 30V.)
Any normal/healthy 12V vehicle is fine for this chip.
Hi,
Thanks for support, this means that I will build the amp with the 220V power outside the box, so I can change 12V power when needed.
I'm progressing with my planning, some questions:
1) About the tone stack: what kind of capacitors should it be (I've seen different types and I assume they have different power ratings?)
2) I've browsed around ebay, but haven't yet found a supplier for all components (alu box, chicken knobs, potentiometer, capcitiors, tele jack, etc). Do you have any preferred ebay supplier you can recemend? Preferably in EU, but US should be ok as well.
Thanks,
Jakob
Just like to say , after all this time , I still really Like the sound and performance of the TG .... No problems to report once we eliminated the Hum by going to a 3 prong power supply ... Good sounding amp ... !!!! :icon_mrgreen:
Starting on my second TG ... Just for FUN !!! :icon_wink:
Just building mine up and noticed this. I just cut off that little cylinder...do I need it? I was going to hardwire the supply to the board. One other thing, my supply does not have a ground but from the sounds of it, some here haven't needed one? Thanks.
Quote from: Keeb on February 25, 2012, 05:56:59 AM
Quote from: DocAmplify on February 24, 2012, 07:26:21 PM
On that note, my laptop DC has something attached to the cord on the DC side (it's a small cylinder - smaller than a size C battery). I have noticed this on multiple AC to DC converters on the DC side. What is it? I already cut the stock end off and soldered my power end, but I want to replace it. Cutting it again will put me very close to this widget.
A ferrite bead perhaps?
http://en.wikipedia.org/wiki/Ferrite_bead (http://en.wikipedia.org/wiki/Ferrite_bead)
Yeah sounds like a ferrite bead, it will work fine without it, I cut the one off my power supply so I could fit the correct plug. Mine is only 2 pin, no ground and works fine, hopefully yours will be Ok.
Cool thanks for the speedy reply, I am excited to get this thing going!
Cheers!
The ferrite bead keeps the digital trash inside the laptop from getting out the power cord and messing-up your TV and radio reception.
Since this Giant is not a PC, not any kind of digital, the ferrite isn't needed.
Thanks PRR!
Quote from: PRR on October 17, 2012, 01:02:41 AM
The ferrite bead keeps the digital trash inside the laptop from getting out the power cord and messing-up your TV and radio reception.
Since this Giant is not a PC, not any kind of digital, the ferrite isn't needed.
is the TG a master volume type of amp?
Hmm. I don't know if that terminology applies to the TG since it's primarily meant to be a clean amp. My understanding is that master volume amps allow for preamp overdrive because they have tube preamps, but you don't really want to overdrive the front end of this amp. The power amp does sound interesting distorting though.
I have some plans to box mine up with a valvemaster in front of it then tune the valvemaster out put down to not overdrive the TG.
Then add a stomp/switch that will change between clean and dirty on the valvemaster.
Also throw in a simple Bass and Treble EQ for the Gain channel, and maybe just leave it off for the cleaner side....
If I want I could go fine a reverb circuit...
But in the end...
You could have a two channel 12Watt(driving 8ohm) amp head. All for under about 45 to bucks... that is awesome best part being that you would even be getting the sounds of tube break up.
I built the TG but it
sounded like an arriving ferry.
It hums like a giant.. What
could be wrong, Im sure the
components are in correct
places.
Quote from: jogina111 on October 24, 2012, 04:14:07 AM
I built the TG but it
sounded like an arriving ferry.
It hums like a giant.. What
could be wrong, Im sure the
components are in correct
places.
Sounds like it could be a power supply problem. If you had a car battery you could try that and then if there is no hum it is your power supply.
^ http://www.diystompboxes.com/smfforum/index.php?topic=99124.msg874434#msg874434 ;)
oh! It really is the power supply... Is there something that can eliminate the hum like a filter? Would the huminator from beavis audio help eliminate it?
On another forum we're seriously discussing the Tiny Giant , and this was mentioned ... "One thing I thought of regarding the hum some people are getting with two-prong power supplies: looking at the preamp, I see two 1M resistors forming a center voltage reference, and there's no capacitor bypassing noise to ground. Compare that with virtually every op-amp based circuit at RoG, which has a fairly hefty cap from Vref to ground. Perhaps an electrolytic cap across the 1M resistor to ground would...what's the term I saw on other datasheets..."improve supply voltage rejection"? "
Taylor , would you PLEASE join us here to further enlighten us ... http://www.wattkins.com/node/18421?page=3
> center voltage reference, and there's no capacitor bypassing
The original design has a regulated supply.
If running on unregulated wall power, you probably need to change that bias circuit ala RoG and similar plans.
Hallo,
I just got my tiny giant boxed up and wired and everything, and I'm having a problem. Maybe someone can point me in the right direction?
Basically, everything up until the TDA is good, I'm getting 11.6v where I need it to be, I'm getting signal to pin 3, and the volume pot works just dandy. (dandily?)
However, when I turn up the volume past a certain amount, it starts to clip and then all of a sudden a very loud sputtering sound :o
I've reflowed my joints and checked for weird connectivity to ground, of which there is none, I've gone so far as to route the speaker wires as far apart from eachother as possible as seems to be prudent from other posters earlier in this thread, but even in a shielded box this is happening. I'm not really sure what else to do but try and source another TDA and pitch this one.
Any pointers are much obliged!
Thx
At what point on the volume knob does it start to do this? What are you plugging into it?
got the same problems..when volume pot on 12 o'clock, it gets to stutter mode with my guitar plugged with the bazz fuss. When vol pot is on about 4, it splutters even if Im not strumming...is it the power supply? Cuz Im using a 1.3A power supply and tweaked the TG to run at 12v... Maybe it need more current? How must we connect a preamp directly to TG using the hole provided to power the preamp? Must it be a cheater connection? Or the ground on the preamp must be connected on TG's ground?
I had been using a guitar, with similar symptoms, but I got kinda tired of reaching over to strum it all the time :P
So now I have a sine wave generator putting through a signal at about -30db
It starts off sounding fine as I go up from 0, then at around 11oclock it starts to get kind of fuzzy, and then at 12oclock it starts to make these quite loud popping sounds that seem to react to my playing. Sometimes they go away when I stop, but other times I have to turn the volume down. I guess it's oscillating or something?
UPDATE:
I was just dicking around with it some more and I wiggled the capacitors near the TDA, the 470uF and the 10uF kind of at the same time and it fixed the problem! I had reflowed them, maybe i damaged them or something. jogina111, that might be a good place to start if you are having the same symptoms as me. so I'll be swapping those out. :D
thanks for being around, Taylor. I built up an echo base from your pcb last month and it fired up first shot.
EDIT:
jumped the gun, goddamnit. swapped out those caps and it's still happening. i swear i had it going for like 20 seconds! bah
Would it be possible to run 2 tg boards in a stereo setup with 1 powersuply and a dual taper volume pot without any problems?
Quote from: Cerberus on November 05, 2012, 02:56:13 PM
Would it be possible to run 2 tg boards in a stereo setup with 1 powersuply and a dual taper volume pot without any problems?
Yes, I've done this successfully. Make sure your power supply can handle both boards.
Hey everyone - finally got my TG going and I am having some of the same issues as just recently mentioned. Clipping badly at around noon and sounding like fuzz and cutting in and out when maxed. Took some numbers and everywhere the schematic shows 11.6v, I am getting 11.35v with a power supply of 16v and 4.5amps. On the schematic it shows the LM338 Vin at 19.5v and my reading is 16.66v. So far are these readings causing any issues that anyone can think of? Further prior to populating the board I measured all the parts and only one came up considerably off, the 470uf cap was actually 370uf, would this cause an issue? Just a thought, could a bad POT cause some of these symtoms? I'm a noob so...go easy on me.
Thanks.
Nick
Hi Nick, welcome to the forum. The 19.5v is only if that's the voltage of your power supply, so with a 16v supply it's not surprising that you get ~16v there.
I have to admit that I don't know the cause of the cutting out because I have never experienced it. I don't have any place where I can turn it up to maximum - just too loud for the places I can use it. Some amount of distortion is to be expected and could be considered a feature, but cutting out is no good. I will try to reproduce it and see if I can figure out what's up.
Thanks Tyler. I checked and reflowed my joints and swapped the TL072 and still basically the same, maybe a bit better. After playing the amp again, I would recharacterize my previous assesment, not really clipping "badly" at noon but is clipping a bit. Here's something else I noticed, when the volume is all the way up, that is when it kind of cuts in and out and fuzz type sound. It does the same when hitting the front end really hard with a Madbean Sunking. So, when I pull the volume back just short of full and dial the Sunking back as well, I basically get the same amount of volume but with no cutting out or fuzz. Seems to be ok, not sure what it is about the total cranked position that it doesn't like.
what do you use for a power supply masterlk?
Some clipping is to be expected, and several people have mentioned how much they are surprised that it clips nicely, unlike many solid state amps.
The preamp is a plain old opamp so there is nothing to be gained by slamming the front end with a booster or whatever. A tube will break up in an interesting way when you do this; an opamp won't.
For this amp I am using a 16v 4.5amp laptop ps.
Posted by: jogina111
Insert Quote
what do you use for a power supply masterlk?
Ok and thanks. My appologies for calling you Tyler in my previous post, sorry. I am going to box this thing up and call it good!
Some clipping is to be expected, and several people have mentioned how much they are surprised that it clips nicely, unlike many solid state amps.
The preamp is a plain old opamp so there is nothing to be gained by slamming the front end with a booster or whatever. A tube will break up in an interesting way when you do this; an opamp won't.
Quote from: Taylor on November 12, 2012, 12:49:26 PM
Some clipping is to be expected, and several people have mentioned how much they are surprised that it clips nicely, unlike many solid state amps.
The preamp is a plain old opamp so there is nothing to be gained by slamming the front end with a booster or whatever. A tube will break up in an interesting way when you do this; an opamp won't.
I'm planning on using one (or maybe two, with switching) of the ROG circuits as a preamp with this. Was thinking either the Professor Tweed or the Azabache, along with the Matchbox for channel 2. Should I therefore leave out the preamp stage that's in the TG circuit, or am I OK to just add on the ROG circuits in front of the whole thing?
Either will work, so if you just want the simple path I'd leave the TG preamp in and just add your new preamp in front as if it's a pedal.
I've got an old power supply from an old PC and Im planning to hack the 12v transformer plus the regulator to make a power supply for the tg...but when I checked the labels, it says 12v-~15amp. 15 AMPERES! Can the tg take that much current? im kinda afraid to just make a PS so I asked just to be sure.
Electronics will only draw the amount of current they need, so it will draw only an amp or so regardless of how much the supply is capable of handling. So you'll be just fine.
BUT. The rules of helping on forums require that I tell you that working with mains power is dangerous, and if you don't know how to do it safely, you shouldn't be doing it in the first place. If you have any uncertainty about what you're, that's a sign you're not ready to work with high voltages and you should get a friend who knows to help.
Sorry to be disclaimer-ish but I don't want anybody to get hurt, and more importantly, I don't want to get sued by your family. :icon_wink:
Why not just tap the 12v from the normal output connector on the computer PS instead of canibalizing it? It might be bulkier, but you wouldn't have to put it in another enclosure and it would be much less likely to be a safety hazard.
thanks Taylor and John. Im not very insistent to try hacking the psu now... but my knowledgeable friends might do know how to manipulate electricity so I'm asking them for help.
Hi,
Started to solder my Tiny Giant and realised I'm a real noob on this :)
Some holes on the PCB doesn't seem to have any component that should be soldered to them, I marked them with red circle in below picture. Should I do something else with them?
(http://img195.imageshack.us/img195/290/tinygiantpcb.jpg/)
http://img195.imageshack.us/img195/290/tinygiantpcb.jpg
Thanks,
Jakob
You don't do anything with those holes. The board is double sided, meaning it has traces connecting components on both sides of the board. Those holes are called vias and join traces on the front to traces on the back.
A friend of mine who builds amplifiers answered a dumb question I had with, "when you're not sure if oranges and soy sauce will taste good together, you should try it, and see what happens." He left out part B for dramatic effect, but he was implying that dealing with power supplies and mains is not something you should "try".
Quote from: slacker on November 24, 2012, 01:08:30 PM
You don't do anything with those holes. The board is double sided, meaning it has traces connecting components on both sides of the board. Those holes are called vias and join traces on the front to traces on the back.
Thanks! I'll continue solering :)
I think the problem with sputters is when the lm338 heats up. Ive fixed mine by getting a larger heatsink for the 338.
Hello, I have a little question , maybe its stupid, but her it is.
Im waiting my kit for a long now, beacause i live in small country estonia, im realy waiting it:) So thanks taylor for the great amp!
So i wana add tonestack, if this one is going to work?
http://amps.zugster.net/articles/tone-stacks#18Watt
...:)
> i wana add tonestack
Try it without. A good clean flat amp is a different experience from an over-complicated amp, and you may like it for some work.
> if this one is going to work?
(http://amps.zugster.net/images/articles/tonestacks/18watt-schem.gif)
No. Or not real well.
The "18 Watt" is a tube amp. This tone network goes between a tube of medium output impedance (~~40K) and a tube of high input impedance (1Meg?). Even if I did not know that (or are too lazy to look it up), I could guess that from the high pot values, 500K, and the way the tone pot puts a capacitor right-across the source.
The same area in a Tiny Giant has a super-low output impedance (op-amp, ~~1 ohm) and a low input impedance (10K pot and ~~20K chip input). Will suck all the sound out.
There is a TG-adapted classic tone control on page 5 of this thread:
http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg768743#msg768743
For 2-knob, make the "Middle" pot a 680 ohm (470 to 1K) fixed resistor.
For 1-knob, also make the "Bass" pot a 2K to 5K fixed resistor.
If you are in love with the 18W's one-knob, try this:
(http://i.imgur.com/pkQvZ.gif)
All values scaled by a factor of 50 to suit the chip-amp's lower impedances.
Values not critical. +/-20% is no difference (so use 0.47uFd and 2.2K). Tweak to taste, which may mean going 4 times higher or lower than what I've suggested.
Are there any sound clips of this?
I tried searching youtube, and this thread just searching for sound clip, no luck.
Also Would there be any reason you couldn't replace the pre-amp section with a stomp version of a fender amp, say like the wampler tweed 57 or black 65?
Quote from: pappasmurfsharemAlso Would there be any reason you couldn't replace the pre-amp section with a stomp version of a fender amp, say like the wampler tweed 57 or black 65?
Buy the kit from Taylor and build it in 5 minutes. Then breadboard a bunch of RunOffGroove projects and decide what you like then box it up and have it for whatever amp you might be playing out of. Why remove the TG's input buffer? Leave the TG alone (perfect for what it is: clean, loud, easy, cheap) and build two different sounding ROG projects in the same enclosure, say, Fender style and Marshall style.
Quote from: garcho on December 23, 2012, 01:55:07 AM
Quote from: pappasmurfsharem
Also Would there be any reason you couldn't replace the pre-amp section with a stomp version of a fender amp, say like the wampler tweed 57 or black 65?
Buy the kit from Taylor and build it in 5 minutes. Then breadboard a bunch of RunOffGroove projects and decide what you like then box it up and have it for whatever amp you might be playing out of. Why remove the TG's input buffer? Leave the TG alone (perfect for what it is: clean, loud, easy, cheap) and build two different sounding ROG projects in the same enclosure, say, Fender style and Marshall style.
I just figured it would be nice to have a fender style preamp, that would have some sort of 3 knob eq and have separate gain and volume knobs that would respond similar to an actual fender.
Are you saying just run those directly into the current pre-amp of the TG?
Yeah, just don't think of it as a tube amp that sounds good when you drive the pre. You just need dirt and EQ, might as well do that with a pedal and get more usefulness and variety than hard wiring it into the TG. If you do alter the TG, remember you're not necessarily using 9V.
Yes, the TG is so pedal friendly , no use mucking about with the amp itself ... it WORKS !!!! Anything(pedal) up front sounds Great through it !!! :icon_mrgreen:
Hi,
I tried my TG combo first time today, some issues:
- I got some hum/noise, but I assume it's the power supply or lack of shielding (it's quite close to the speaker magnet..)
- Whats worse: it giving quite a distorted sound when I increase the volume... If I was a rocker it might not be a problem, but I'm into jazz, so I'm after a clean sound...
Any comments on above is appreciated..
Regards,
Jakob
When you say increase the volume, where on the dial do you have it when it starts distorting? What kind of instrument and effect chain are you using?
Sorry if this has been asked already (did a quick check and didnt see anything), but what size is the pcb?
it's 1.5" by 1.125" or about 4cm by 3cm
Hi !
I ordered the TG amp kit and I was wondering if I can use this speakers...
(http://i1153.photobucket.com/albums/p508/patulo67/Picture006_zps7246eae4.jpg)
This are 5 inches 6 ohm speakers that i have collecting dirt for a while... Should i wire them in series or paralel?
me again...
one more question...I intend to build this kit as a little practice amp, use it for test my pedals...What if I put a circuit like runoffgroove's english chanel..?
QuoteI intend to build this kit as a little practice amp, use it for test my pedals...
Then by all means, DO NOT hard-wire a ROG project into the TG. I love ROG, I've made a lot of their projects, but if you want to test your pedals on the workbench, nothing will be better than the clean and loud TG (until it's time to tweak the details - then use your 'real' amp). By all means, build a ROG project into a stompbox and use it in front of the TG for some color/dirt.
Series vs. parallel. (http://en.wikipedia.org/wiki/Series_and_parallel_circuits) If both speakers are 6Ω, wiring them in parallel would give you 3Ω. You can burn out your amp that way. Wire them in series, and you get 12Ω, which is probably higher impedance than you need. Try using only one of your speakers.
I bought a cheap Jensen for my TG; it sounds fine. I suggest using a guitar speaker if you can get your hands on one, or at least an instrument speaker (accordion, bass, etc.).
thank's for the advice !!! my intention was to make it sound like an AC-something, but i think i'll keep the way it was meant to be...
as for the speakers, 3 ohmm willl burn my amp..? (this is maybe a stupid question). In the future i'll put a 12" guitar speaker, but for now i guess i'm going to do it with those 6 ohms...
^ Speaker coils are long pieces of wire. The more you place in parallel, the lower the resistance, just like resistors. The lower the resistance, the closer you are to a short circuit. Amps don't like you to short their outputs ;)
Quoteas for the speakers, 3 ohmm willl burn my amp..?
roughly, in Chicago dialect:
more ohmage = less wattage
less ohmage = more wattage
Those are wonderful speakers, but one or even two will NOT take the full output of a 20 Watt amplifer doing overdriven guitar.
Two in *series* makes about 12 ohms and with this amp will absorb 5 Watts total, 2.5 Watts each. A good rating for these speakers on _RAW_ (overdriven) audio is 3W each, so 2.5W each 5W total is just about spot-on.
Two dinky speakers is not going to give the chest-pounding Authority that a proper Guitar Twelve will. The pair has about 1/10th of the air-pushing area of a Twelve. Like paddling a canoe with a large salad-spoon. It will go. It may go good enough for canoeing a swimming-pool or playing a workbench. But a Twelve (or similar) will give a lot better grip on thin air, and a much bigger sound.
Quote from: Taylor on December 25, 2012, 07:29:17 PM
When you say increase the volume, where on the dial do you have it when it starts distorting? What kind of instrument and effect chain are you using?
Hi,
Did some more testing, separating the TG from the combo. It drives my 10" well and loud, the distortion is gone. In my "combo" I have a 3,5" speaker (a quality Peerless speaker with high wattage etc, 8 ohm) in a 2 litre cabinet. Either the cabinet which is not 100% finished yet caused some distortion/noise or the that the TG was inside the cabinet without proper shielding... I'll rethink and put the the TG in a separate box...
=> Where do I buy a suitable metal box? Like the one in very first post in this thread?
There is still some small noise/hum which increases when I turn the volume up. Maybe a shielded box will help? Or can it be my HP laptop power unit?
Regards,
Jakob
"=> Where do I buy a suitable metal box? Like the one in very first post in this thread?
There is still some small noise/hum which increases when I turn the volume up. Maybe a shielded box will help? Or can it be my HP laptop power unit?"
https://www.smallbearelec.com/home.html is a good place to buy most guitar related electronics, and they sell boxes just like the one in the first post, in different colours too. I suggest you also buy some other components for any other projects you have going, to save on shipping (the prices are comparatively low for most components at small bear)
As for hum, it wont be the power supply for the TG, because it uses a voltage regulator, which gets rid of nearly all power supply ripple. It might be power supply ripple from something else you have between your guitar and the TG, but it's probably hum from your leads, your guitar and the TG not being shielded.
I hope that helps
Hi,
Thanks psychedelicfish for answer, it helps. I found a case locally here in Sweden, not as neat, but with some extra space for 9V regulator etc.
Let's see if the hum disappears when I get the TG boxed.
Thanks,
Jakob
I'm a novice jumping into this one a little bit, my electronics has only been going about a year:
FIRST - 20W output means roughly 30W input for a solid state amp like this?
SO - Running off 18V, the amp would draw about 1.7A?
THEREFORE - if I wanted this to be a portable amp, I'd be looking to have two lithium 9V batteries in series, but lasting less than an hour, (Lithium 9V ~1200mAh)
Are my rough calculations about right on this, and if so, what other battery/cell solutions could I use?
I know i'm being ambitious with a wireless Tiny Giant, but I'd like something a bit more than a 'noisy cricket'. Is there an intermediate stage, perhaps 8W to 15W?
Quote from: gcme93 on January 04, 2013, 07:20:20 PM
I know i'm being ambitious with a wireless Tiny Giant, but I'd like something a bit more than a 'noisy cricket'. Is there an intermediate stage, perhaps 8W to 15W?
I've built this one for use with a 12v sealed lead acid battery, great for busking.
http://xtronic.org/circuit/amplifier/audio-amplifier-potency-circuit-tda2030/
It's around 12 Watts into 4 ohms, or 8 watts into 8 ohms speaker.
It uses a TDA2030, which was designed for car radios, so works great from 12v. It's just a power amp, so you will need to add a preamp to it.
I actually used a Colorsound Overdriver pedal as the preamp, so I can use it clean or add some overdrive/distortion. And it all fitted quite nicely into an old Squire 10w amp that I gutted. I'm running it with the original 8 ohm speaker from the Squire, and it sounds good, if I can find a nice 6" 4 ohm speaker I'll upgrade to that for more oomph.
> Are my rough calculations about right
Yes.
But... the chip is really made for 12V (car) battery. The 17V was just a handy (cheap) plug-in supply, which has to be dropped for the chip. That's a waste. You want a 12V battery.
As Alan says, there are many good choices around 12V 2AH. Fire alarms and exit lights often use such a size so they are available at home-stores. The smallest motorcycle or lawn-tractor battery may busk all day, though the cheapest types are prone to spill acid.
Thanks a lot Alan and PRR!
One last thing, am I now okay to leave out the LM338T altogether now? I understand exactly what you mean about the excess voltage being a waste! The rest of the schematic only runs off 12V! I was planning to create my own vero layout, so I'll just have the 12V hooked straight up as written in the schematic.
Again, sorry for the ignorance on my part, but do I need any protection on this V+ line to stop chips frazzling? I was thinking that a battery doesn't have the same potential for power surges like a wall supply, but I can never work out on my own where the random RC filters and things are needed...
Then again, I may also add in a power supply option as I have some 12V/13.5V plugs around (yes I'll check they'll supply enough current!), so if I do, I'll just add in the regulator as on the schematic
Thanks again for the help,
George
Something I'd like to try but haven't got around to, is using a cordless drill battery. Rechargeable, small, cheap enough to buy two and always have one going. I'm probably missing something obviously wrong with that set up, but might be worth noodling around with.
The problem with most cordless drill batteries is that they are designed to connect to the cordless drill, and don't have an easy way to hook up wires to connect it to something like an amp. Whereas a 12v Sealed Lead Acid battery normally comes with lugs so a standard connector can be used to make a cable to power your amp. They are also available in a range of amp/hour ratings.
Quote12v Sealed Lead Acid battery
are they rechargeable?
Yes. That's what you normally get in an uninterruptable power supply (UPS/battery backup).
QuoteThe problem with most cordless drill batteries is that they are designed to connect to the cordless drill, and don't have an easy way to hook up wires to connect it to something like an amp.
I like Lithium power tool batteries. They are light-weight, and have high energy density (lots of power for the size). You might be able to build a connector for one by scavenging it from a dead tool or charger, but I just do this - a couple small pieces of PCB cut to the size of the contacts with wire soldered on - an o-ring or two (like a rubber band) to hold them in place - and a couple small pieces of wood glued on so the o-rings can exert some pressure. Works very well.
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=42309&g2_serialNumber=2)
Good idea Walt. that would also give you a much higher range of voltages to use, could build a nice powerful battery amp with an 18 or 24 volt one.
> are they rechargeable?
Lead-Acid is the ordinary car battery. Play the radio until the battery is flat, get a jump and run the engine a while, the battery is full again. Without an engine you can use a battery charger from a wall-outlet.
Yes, it is nasty technology. The acid will rot your shirt and your skin. (In a dead-short, a car battery can boil your face off.) When the lead cruds-up and we throw it in the woods it poisons the earth.
But it is also reasonably good energy density, and fairly inexpensive for the energy.
And there are versions which do not leak acid. An EXIT sign or underdesk UPS should not be dripping scuzz, those cells are totally sealed. We have a car with battery in the trunk, sealed so it won't soil the luggage. Motorcycles used to use a vented battery where outgassing was less likely and if it happened it all came out a tube you could aim away from the frame or your leg. Lawn-tractor batts are this type.
Ni-Cads served us well for 70 years but are going out of style in a hurry.
> I like Lithium power tool batteries.
Yes, now that production is mass and prices have come down, I use Lithium more and more. I do wonder about the long-term effect of concentrated Lithium trash on the earth (we have not yet trashed as much Lithium as Lead). I do worry that the rush to high energy at low prices encourages marginal construction (cell-phones burning backpacks, etc). I'm actually still using Ni-Cad tools but it is clear the tool makers are discontinuing that and moving us to Li-Ion.
I'm looking at something like this:
http://gb.dinodirect.com/rechargeable-lithium-battery-12v-4800ma-cctv-camera-d-12480.html?vn=RGlub2RpcmVjdEZ1Y2s&AFFID=33
Seems to fit the bill? and a normal size, connector, even includes a charger!
Final question is this:
Do I need any capacitors or anything to protect my circuit from current surges, too high a voltage from battery etc? I'm planning on using a simple diode setup to protect against connecting the battery the wrong way around.
Sorry if this is a beginners question, but I would definitely count myself as a beginner - only one pedal and a small radio to my name
Thanks for all the information on this topic!
G
Hello everyone: First time poster - long time lurker
I purchased this kit with the components about a week ago now. Soldered the board no problem (really nice PCB!) have how I have only had marginal success getting it to work properly. I've read through the posts here and done as many tests/fixes as are recommended now but I guess it's time to bite the bullet and ask for help.
SYMPTOMS: When I first fired it up, it sounded fine except it would cut out slightly when the guitar's volume was down almost like it had a noise gate. a little crunchy when cranked which was cool but I had wired the pot backwards too so I opened it up. Resoldered the pot the correct way and put it back together. The same 'noise gate' type effect was significantly more pronounced as well as some very nasty clipping. I double checked for grounding between the case and the LM338 and confirmed there was no issue there (also no issues grounding on the speaker jack.
It worth noting that both of the SPST switches ive tried have done absolutely nothing. Not sure why... maybe this is a clue to my problem? I've also tried it with nothing in the bypass slot with no changes to my problems.
The voltage coming out of the hole following the "MUSICPCB.com" print measures 15.5v
Thank you all for looking at this
Welcome! You came to the right place for help. We're gonna need a little more information to help you figure out what's going on.
Can you measure the voltages on the opamp pins?
Can you post some good pictures (top and bottom of the PCB and how it's connected in the box)?
-Walt
Firstly, here are pics - my wires are a bit long still - once i get it working I'm gonna tighten them up a bit.
Back of the PCB
(https://dl.dropbox.com/u/6700296/IMG_2300.JPG)
The Enclosure (the two white wires lead of to the SPST)
(https://dl.dropbox.com/u/6700296/IMG_2288.JPG)
So, I'm assuming the opamp is the 8 pin chip that plugs into the 'holster'? Thanks, Walt
Ok, so I measured both. The TDA is the opamp and the TL is the regulator?
TDA7420A shows all 0v except for pin 2 (2 pins from the big capacitor) with read 15.6v
The TL072 reads (not sure how the pins are numbered so this is the side facing the voltage in/load out):
pin1: 7.7v
pin2: 7.7v
pin3: 7.3v
pin4: 0.0v
other side (side facing capacitors):
pin5: 15.6v
pin6: 7.7v
pin7: 7.7v
pin8: 7.3v
The TL072 is the opamp. The TDA7240 is the amplifier chip. The LM338 is the voltage regulator.
The dot on the opamp is on the top-left, and the top-left pin is pin 1. The pins are numbered from 1 to 8 down the left side and up the other side, so the pin numbers you gave for 5-8 are reversed.
You substituted a 1500-ohm resistor for the 1k resistor, so the voltage regulator is trying to put out 16.88V. To get that much voltage out, the power supply must be about 1.25V higher than the output voltage you are trying to get. It looks like your opamp is getting 15.6V, so that means your power supply must be putting out about 16.8V. That's not likely to be a problem.
Your opamp is biased at about half the supply, so that looks good - and the other voltages on it look about right.
Your pot is wired correctly.
I don't see anything obviously wrong in the photos, but it's a little hard to make out the details on the solder-side shot, and to see where everything is connected.
It's kind of fishy that the switch connected to the white wires doesn't mute the amp. With no power applied, can you verify that one of the white wires is connected to ground, and the other is connected to pin 2 on the TDA7240?
-Walt
QuoteYou substituted a 1500-ohm resistor for the 1k resistor, so the voltage regulator is trying to put out 16.88V. To get that much voltage out, the power supply must be about 1.25V higher than the output voltage you are trying to get. It looks like your opamp is getting 15.6V, so that means your power supply must be putting out about 16.8V. That's not likely to be a problem.
My power supply is rated at 16v 4.5a so I guess this may be an issue. My desire for gain gets the better of me sometimes ;) I'll swap this with a 1k resistor when I get home today and see what changes.
As far as the SPST goes, I can confirm continuity with both the ground and pin 2.
the circuit is designed to work perfectly on 12v , 11.6v to be precise. Subtituting the values of the resistors on the regulator section will change the voltage and may damage both power and preamp sections of the amp.
QuoteMy power supply is rated at 16v 4.5a so I guess this may be an issue. My desire for gain gets the better of me sometimes I'll swap this with a 1k resistor when I get home today and see what changes.
You can try that. It definitely won't hurt.
QuoteAs far as the SPST goes, I can confirm continuity with both the ground and pin 2.
Hmmm. That's puzzling. If pin 2 is grounded, the chip should be in standby - and no sound should be coming out. If it's true that the switch has no effect, and you still get sound output, then I would think that there's an open circuit somewhere between pin 2 and ground. When you checked continuity, were you testing pin 2 from the top side of the board? The reason I ask is that if you have a cold solder joint, it might not be making contact with the pin (and if you have one cold solder joint, you might have others.) ...or maybe the switch itself is bad.
Your original description of symptoms (noise gating/nasty clipping) makes me wonder about the preamp section. Did you ever put the opamp in the socket backwards and apply power? Do you have another opamp that you can try in place of the original one? Did you ever try running it outside of the box?
1. I have a 8Ω/15W practice cabinet. In a normal situation the Tiny Giant outputs 12W at 8Ω. Is it maximally safe then, or shall I lower the supply voltage a little, to gain something like 10W at 8Ω output? I'm asking because of component's tolerance. You know, the 120R and 1k resistors that control the supply voltage can differ from the desired values, making the voltage higher, etc.
2. It's said that TG needs a 4A or more PSU. Isn't it like ~2 times the real value? I was once playing with a 2xTDA2003 kit, and it was supposed to draw as much as 2,5A.
3. If I have a decent 12V regulated supply I can omit the LM338 part, right? But what is better? Additional security(?) of double regulation, or just getting rid of another heat generator? Also, wouldn't powering the amp from 12V (not the usual 11.6V) raise output power too much for my cabinet?
4. I was thinking of packing the TG in an enclosure along with some sort of preamp, but I might as well stick to using stompboxes. However, I've heard people complaining about the flat response, or the TG not being guitar amp-like. Would adding the classic tone stack as once suggested by PRR deal with that issue?
Thanks in advance.
If the "15W" rating is for Guitar Amp Use, you are fine. Guitar speaker makers have learned to build strong and rate low, or else guitarists kill them too often.
5% resistor tolerance or 11.6V:12V difference is not a big deal.
You can't "double regulate" 12V then 11.6V because the on-board regulator needs a volt or two of excess to do its regulation duty.
If you are still very concerned about speaker blow-up (or it is just a bit too loud?), put a 4 ohm 10W resistor in one of the lines from PCB to speaker jack. This will cut power to around half, and also lighten-up the speaker damping giving a more lively sound from the speaker (more bottom thump, more scream).
Yes, the 4A spec for power is very generous. That comes from Tayor finding Laptop PC power supplies at VERY low prices, and these are usually 4A or more. I doubt it really eats 2A, but the extra does not hurt.
Quote from: PRR on January 16, 2013, 05:33:17 PM
If the "15W" rating is for Guitar Amp Use, you are fine. Guitar speaker makers have learned to build strong and rate low, or else guitarists kill them too often.
The speaker is Celestion Super 8, so it speaks for itself.
Quote from: PRR on January 16, 2013, 05:33:17 PM
You can't "double regulate" 12V then 11.6V because the on-board regulator needs a volt or two of excess to do its regulation duty.
Ugh, of course, I just forgot about that. So let's put it like that - is it better to buy bigger voltage PSU and use the onboard LM338, or is the regulation in those chinese power supplies good enough for TG thus allowing to omit that specific part in TG, so less heat is generated during operation? Price is the same for 12V and other voltages PSUs, but most likely I'd find some kind of laptop PSU at my house.
Quote from: PRR on January 16, 2013, 05:33:17 PM
If you are still very concerned about speaker blow-up (or it is just a bit too loud?), put a 4 ohm 10W resistor in one of the lines from PCB to speaker jack. This will cut power to around half, and also lighten-up the speaker damping giving a more lively sound from the speaker (more bottom thump, more scream).
Good to know. Will consider doing.
Quote from: PRR on January 16, 2013, 05:33:17 PM
Yes, the 4A spec for power is very generous. That comes from Tayor finding Laptop PC power supplies at VERY low prices, and these are usually 4A or more. I doubt it really eats 2A, but the extra does not hurt.
Just as i thought. As I said, most likely I already have that kind of PSU. Asked just from curiosity.
Anyway, I'm still concerned about the tone stack that you mentioned earlier in the thread.
http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg768743#msg768743
Will it make TG sound more like a guitar amplifier? I'm pretty sure it will, but what's your opinion?
[EDIT]
Here's something that I think would make a better use of the dual opamp in TG.
http://deanmarkley.com/Info/LegacyAmps/Schematics/D1508.pdf
I have heard it sounds good, so I want to try it. It's also paired with a chip power amp, so if I wanted to use it permanently, shall I omit the buffer/preamp part of TG, and connect it directly to 1uF cap just before the TDA's input?
As you can also see it's meant to be powered by dual rail supply. How to deal with this? There's a kind of DC version of this combo (http://deanmarkley.com/Info/LegacyAmps/Schematics/D1536.pdf), but it uses a sh*tload of additional components, and I prefer the simple ideas.. Would the old resistor trick be any good for this?
Hei,
i finally got my kit, and this little amp is amazing.
i made a rehersal with that, and it sounded quite good with my mxr stomps.
Heres my build, not ready jet.
(http://sphotos-b.ak.fbcdn.net/hphotos-ak-ash4/485914_516494281729154_1320421005_n.jpg)
Whoa! I love the look of that, seriously. Really cool.
Still one question.
if i use this heat sink.
Should i use vent? or isit okei.
(http://sphotos-c.ak.fbcdn.net/hphotos-ak-ash4/376524_516689331709649_2059452770_n.jpg)
> Should i use vent?
Play hard. Put your finger on the heat-sink.
If you can hold it as long as you like, it is fine.
Looking at that one, I think it is entirely fine if you mount it upright, so both sides have a free flow of air.
This was a great build.
The PCB was excellent and great to work with.
The local Radio Shack had a 10K audio pot with a switch. This seems to work great.
The Pilot Light was also from there and it would handle the voltage range from stock to enhanced.
I put in a toggle switch to flip between the 1k and 1.5k resistor for a "boost" feature.
future builds will keep the 1K and simply mount the Input Jack on the front of the case.
(http://www.boehm.us.com/images/little1.jpg)
(http://www.boehm.us.com/images/little2.jpg)
(http://www.boehm.us.com/images/little3.jpg)
(http://www.boehm.us.com/images/little4.jpg)
(http://www.boehm.us.com/images/little5.jpg)
(http://www.boehm.us.com/images/little6.jpg)
Here is my new build, its a birthday persent.
(http://sphotos-e.ak.fbcdn.net/hphotos-ak-ash4/408519_520486911329891_1370257276_n.jpg)
Beautiful box!
I'm looking to make a pretty small amp with a few simple effects in for acoustic guitar. Actually I will make two of them eventually. I'm hoping to encourage two different girls one in England and one in Denmark to invest more time in their guitar
playing, they both have excellent voices but could play better.
I found this today:
Speaker Dual cone type
Woofer 13 cm, polypropylene cone type
Max input power 120 W
Rated input power 30W
Impedance 4 ohms
Sensitivity 90dB/W/m
Frequency response 40-22,000Hz
Mass Approx. 590 g per speaker.
I know nothing about speakers, would this be useful in this context? It is a car speaker with a plastic cone which sounds dubious, but it looks cool and what do I know? :D
(http://s1.pokazywarka.pl/bigImages/711605/2140284.jpg)
I'm not a speaker expert, but the specs definitely match up to what you need. From what I've heard (excuse the pun), you can't really tell until you hear them. If they did have too much response in certain areas, and not in others, you could always compensate with your EQ design?
It's likely that a speaker designed for Car HiFi audio is going to have a bright response throughout, not a mid focused response like guitar speakers, so you might be able to find a simple cab emulator circuit to play around with in front of it?
As I said, I think you can't really know unless you've tried them
QuoteSpeaker Dual cone type
Woofer 13 cm, polypropylene cone type
Max input power 120 W
Rated input power 30W
Impedance 4 ohms
Sensitivity 90dB/W/m
Frequency response 40-22,000Hz
Mass Approx. 590 g per speaker.
I've tried a few car audio speakers. They'll probably sound tinny and underpowered unless you mount them in an appropriate enclosure. I was kind of shocked when I first figured out what a huge difference the speaker cabinet makes. If you build/test without putting them in an enclosure, be prepared for them to sound awful (until you get them mounted).
The Tiny Giant itself has full-range response, so you might want to put a simple low-pass filter in front (or a cab sim as already mentioned).
> an appropriate enclosure.
A 5-inch speaker, just naked, has bass roll-off of everything below 1,300 Hz.
(Not _so_ bad on larger cones.)
It is a car door speaker. Put it in a 2-foot panel of heavy cardboard, it has bass to 250Hz. Put that panel in a door, so the back-wave hardly comes out, it has pretty-much all the bass the speaker can give.
You can also start with a 3-foot panel and bend the edges back. It becomes basically a Twin Reverb size. Makes sense when you want two 10"-12" cones. And that rig would make good sense for the Tiny Giant.
If you want a bedroom rig: multiply speaker size by 1.1. About 5.6 inches. Imagine a closed cube 5.6" inside. But when you build it, stagger the dimensions 1.2 or 1.5. Since 3.5" is a common size for window trim lumber, perhaps 3.5" * 6" * 8" inside. Don't be exact. Smaller will bump-up the midbass, which may be nice in a gut-less speaker. Bigger will slump the midbass and extend the deep bass.
> put a simple low-pass filter in front
First off: if it sounds wizzy, use a sharp razor and cut off the wizzer cone. They don't work for guitar. Not just IMHO, look at "real" guitar speakers. Even though the E-V SP-12 had a half-good whizzer, the EVM-12 derived from it does not. Wizzers are for complex mixes, FM pop-music, not simple clean tones fresh out of your hands.
The "120 Watts" is totally bogus (so are the other numbers, except size). However it is designed for 12V-14V bridge-mode car radios. The Tiny Giant is a car-sound chip working at 11.5V. An exact fit with a little slack so that crazed guitar solos won't burn the speaker any more than crazed road-trip do.
Thanks guys.
Paul, a closed cabinet 3.5" * 6" * 8" right, but what about the thickness/type of material.
What is optimal? I'm toying with the idea of welding a cabinet out of sheet steel.
I've made similar things before, but I'd probably need to damp the box internally I reckon.
Is it a dumb idea?
> What is optimal?
Whatever is laying around the shop.
For this purpose, 1/4 hardboard would be fine.
In my shop, scraps of 3/4"x3.5" trim are everywhere. I'd do four sides of that stuff, and whatever thin plywood is hanging around the shed for front/back.
> I'm toying with the idea of welding a cabinet out of sheet steel. ...Is it a dumb idea?
Yes. But don't let that stop you.
Are you clever? If you can roll the sides as one strip more/less curved, no flat areas, the ringiness of steel will be moved well above troublesome frequencies. Additionally curving the front/back might be terrific. Think of the oil-tank on a Harley motorcycle.
Just welding six flat slabs together won't suck, but some tones may be over energetic.
It all sounds like more work than whacking some wood.
Thanks Paul, I'll do a bit of research. Starting Monday I'm rebuilding part of the first Danish ship to sail to the Caribbean, and it's a bit of a drive each day, lets see how much free time I get.
^ Ship? I'll bet some teak or mahogany would make a nice cab if you can legally procure some scraps.
It's oak. There was alot of oak about then.
Funny OT story. A couple of years ago the Danish forestry service rang up the Danish navy out of the blue and said "your order is ready".
To which the navy replied "we haven't ordered anything."
"Well we have 90,000 oak trees and all the paperwork, ready to ship."
"What? When did we order that?"
" 1806."
:D
Perhaps I'll be able to tell you if that story is the literal truth after the next five weeks working at the National Maritime museum.
> "What? When did we order that?"
" 1806."
I've heard a similar story about an old English school. After 400 years some roof beams needed replacement. The trustees called the usual lumber suppliers but oak that big was a LOT of money if any could be found. After much mulling, somehow word got to the grounds-keeper. He took down a very old ledger and looked something up, took the admins out in the woods, pointed to a very large mature tree, "that one". Apparently when the building was built, they also planted little trees for eventual replacement of all major beams.
FWIW, I built an amp similar to the TG in a tin shoebox with an old iMac subwoofer. For about $20 it made for an amp with a weird EQ and strange, tuned, pangy reverb. If you have a studio or something, or play venues with lots of channels and mics, it can make for an interesting, unique color that would take a lot of DSP/noodle-time to emulate, for the cost of a few pints. My point is, if you're not trying to build a swiss-army-amp, try experimenting. It doesn't get much cheaper or easier than the TG.
Hey guys, Beginner's question:
I have a 12v 4.2A power supply, and already soldered all the parts to the pcb including lm338t voltage regulator.
If I understand correctly I have to bypass it in order to supply the 12v directly to the board.
What's the best way to do that? (technically - I mean where to connect the +ve wire of the power jack?)
Quote from: shay1510 on February 27, 2013, 04:03:54 PM
Hey guys, Beginner's question:
I have a 12v 4.2A power supply, and already soldered all the parts to the pcb including lm338t voltage regulator.
If I understand correctly I have to bypass it in order to supply the 12v directly to the board.
What's the best way to do that? (technically - I mean where to connect the +ve wire of the power jack?)
http://musicpcb.com/wp-content/uploads/2011/02/Tiny-Giant-Build-PDF-rev2.pdf
Look at the last page of the build guide and you'll see a red text box that labels a regulated power out. You can use that little hole with the black arrow pointing to it to attach your +12V supply
^That would work. The only thing is that you would bypass one of the 100n caps, but this might be OK. Here's an alternative:
(http://i1160.photobucket.com/albums/q485/jdansti/0AB0651D-D4B0-46A7-A5F8-BDE5DD767627-12822-00000C36B2650DE0.jpg)
Hey there,
I used Jdansti's method to connect a 12v PS (omitted the two resistors and the power regulator + a jumper), But I have a problem,
When I connect the power supply the speaker makes a "heartbeat" sound every 3 seconds, wouldn't respond to the volume knob.
Tested with two speakers, same result.
*it also happens when guitar isnt connected.
* it stays the same when I remove the tl072 chip
* when I measure voltage on pin 8 of the tl072 I get a reading of 400mv dropping to 200mv every 3 seconds (which explains the pulsating sound)
does Anybody have an idea?
* Actutally I've noticed now that the PS turn on and off every 3 seconds, once connected. I'll get another PS and report.
Hi there!
anybody tries a DELL PSU, I have the possibility to buy 3 for 25.00 euro, though at the moment I had good results only with an HP one, another one an ASUS didn't work, too noisy also with other pedals, while the HP one is fantastic either in the TGA and with pedals, indeed I have the same HP psu powering the TGA with an additional regulator/filter directly connected to the PSU to power my pedal with 9V.
The DELL PSU model is PA-10 Family Model DA90PSI-00 19.5V 4.62A (as far as I can tell from the zoomed picture I had).
So, is anybody here using this DELL PSU ??
Thanks m8s,
Ciao
Armando
Quote from: shay1510 on March 01, 2013, 07:06:03 AM
Hey there,
I used Jdansti's method to connect a 12v PS (omitted the two resistors and the power regulator + a jumper), But I have a problem,
When I connect the power supply the speaker makes a "heartbeat" sound every 3 seconds, wouldn't respond to the volume knob.
Tested with two speakers, same result.
*it also happens when guitar isnt connected.
* it stays the same when I remove the tl072 chip
* when I measure voltage on pin 8 of the tl072 I get a reading of 400mv dropping to 200mv every 3 seconds (which explains the pulsating sound)
does Anybody have an idea?
* Actutally I've noticed now that the PS turn on and off every 3 seconds, once connected. I'll get another PS and report.
What do you measure at the unused pad next to the "m" where Taylor says you can power external devices?
Also what do you measure on the two pads where you installed the jumper?
Make sure you have your neg test probe on a good ground point.
I think that the 12v PS was defective, therefore I took a 19.5v PS I had laying around
and everything worked (!). The TG sounds great. Need to put it into an enclosure though.
Thanks again.
Glad you got it going!
Hi Folks,
Finally, after some months of having it on the table waiting for an opportunity, I had the time to build my Tiny Giant. Populating the PCB was really fast, the task that took me longer was to prepare the Housing for it.
I've used a Heineken mini-Keg and a car speaker I had laying around. Here you have a picture of the final product:
(http://s9.postimg.org/sczmwtxsv/birrampli_big.jpg)
Simple setup, just a volume knob, and input jack and the DC jack. Sounds great, although I can't use it at high volume as it starts to distort in a naghty way (I think it's the speaker....). I might try to fit a Jensen MOD 5 speaker.
Now that I have it built, I'm already thinking on some mods for it, and one of the things I'm interested in is being able to operate it from a battery. It would be so cool to use it with my friends in front of the BBQ... :)
I've spotted this battery that might work (12v 4500mAh):
http://dx.com/p/ysd-12450-12v-4500ma-rechargeable-lithium-battery-80405 (http://dx.com/p/ysd-12450-12v-4500ma-rechargeable-lithium-battery-80405)
or this one (12v 4800mah):
http://dx.com/p/12v-4800mah-rechargeable-portable-emergency-power-li-ion-battery-91001 (http://dx.com/p/12v-4800mah-rechargeable-portable-emergency-power-li-ion-battery-91001)
But I have some doubts regarding how to wire the whole thing. Ideally I would like to:
-Fit the battery inside the keg (there's plenty of space)
-Be able to run it from battery or from the power supply I have now (19.5v laptop one)
Do you think this battery will work?
Any idea how to put everything together? (the battery should bypass the regulator as it only provides 12 v, while the power supply would use the regulator). Maybe it's better to get an 18v battery instead?
Do you think I can charge the battery from the circuit, or better use the charger that comes with it?
Regards,
Mat
Use the charger it comes with, unless you know for certain what you're doing. Next thing you know, you'll have an expensive battery leaking acid all over your beer. I mean your amp. Sorta dangerous, environmentally hazardous, etc.
I've blabbed a lot about using a 18V 4A cordless drill battery before, but haven't gotten around to trying it out yet. However you do it, you'll want access to the battery, yeah?
Looks good!
I'm looking at the option of an 18v battery and kepp it external, plugging it to the same DC jack... But 18v batteries as more expensive than 12v... :)
I'll think about it tonight while having a beer.
Quote from: potul on April 03, 2013, 03:22:28 PM
I'll think about it tonight while having a beer.
Good plan!
We dont have an LM338T here, what's for sustitute?? Cant find one on google.
You can check an LT1084, I'm not sure if it's a one-to-one replacement, but looks quite similar. Check the datasheet. You might need to tweak the resistor values
MAt
Quote from: potul on April 04, 2013, 09:49:46 AM
You can check an LT1084, I'm not sure if it's a one-to-one replacement, but looks quite similar. Check the datasheet. You might need to tweak the resistor values
MAt
That would be a trouble for me... Idk how to tweak anything, i just know how to read a schematic and build it.
How about LM317??
I think LM317 does not provide enough current. Only 1.5A vs 5A of the LM338
mAT
LM317T?? Is that enough??
this is 1.5 A as well. Not enough
If it is easier to get a regulated 12-14V/4A PS, you could omit the regulator.
Ok,
After doing some tests with my Tiny Giant, I have some questions for you guys:
1- How do you know if the chips are getting "too hot"? Mines are attached to the metal keg, the problem is, it's not a flat surface, so the contact between the tab and the keg is not optimal. I want to be sure I will not fry them.
2-At what levels is it normal to start getting distortion? I can't crank it much without starting to get the sound distorted. I was expecting more clean headroom. At first I thought it was the small speaker, but I tried with a bigger one from another amp, and still distorts at around 25% pot rotation. I've used a linear pot I had, so this should be about 60% in a log pot. Do you see a similar behaviour?
3-If I crank the volume and specially if I feed a distortion pedal in front, sometimes the speaker seems to enter in an "oscillation". It just starts farting with a low freq noise (guitar signal is lost), until I mute the guitar, and then stops. To me it looks like it's a speaker issue, not the amp... but I've never seen this before. If I can I will record a video so you can see it. Any advise on how to avoid this? If I use a guitar speaker (like jensen MOD 5) may I get rid of this?
Regards,
Mat
Quote from: Jdansti on April 05, 2013, 05:50:34 AM
If it is easier to get a regulated 12-14V/4A PS, you could omit the regulator.
I would like to put one so i can use any supply regulated or not..
Please help me
The TG is loud and clean, for what it is. Clean at levels much louder than conversation. It's not a 386, if that's what you're wondering. Think generic car stereo loud.
No point in omitting the regulator, just use any PS that is at least 2V higher than the regulator, which are easy to find and cheap. If you don't use the regulator, the power supply must be regulated. Don't forget it needs to supply a few amps, not 300mA or something.
Right-I misread when he said he "would have trouble with that". I was thinking that he would have trouble finding a regulator. I've spoken with a couple of people who have trouble finding certain parts where they live.
Something to keep in mind is that the TDA amps are designed to operate at vehicle voltages, which are normally 12.6V when the engine is off and about 14V when running. It should even handle a bad vehicle regulator which would allow the voltage to go to 18V. So if you have a regulated supply between 12-14V, you can omit the LM338T if you want. On the other hand, if you've got one and a PS that is =/> 13.5V, you might as well use it. :)
> How do you know if the chips are getting "too hot"?
How hot are YOUR chips getting?
I "like" to be able to hold my finger on it forever; but I'm old and conservative. Modern Silicon can be very happy when hot enough to boil flesh.
> metal keg, the problem is, it's not a flat surface
Bad Idea. A least try with chips outside the keg on a large flat hunk of metal.
Also I bet the keg skin is much too thin to spread heat. You want more like 1/8" 3mm. Small beer jugs are thin 'cuz the beer supports them.
> At what levels is it normal to start getting distortion?
20 Watts into a geetar speaker should get complaint from everybody in the house.
What *knob* setting that is, depends on too many variable to discuss.
> starts farting
Some chips do something like that when over-loaded or over-heated.
Use your finger. (If you can't type afterward, it's too hot.)
Read voltages while you play.
Quote from: PRR on April 06, 2013, 12:17:07 AM
Some chips do something like that when over-loaded or over-heated.
Use your finger. (If you can't type afterward, it's too hot.)
I think you are right, and the issue is what I was suspecting: over-heating of the chip. I did some tests, and if I leave it to cool down it stops "farting" until it gets hot again. So I will need to find a better way to dissipate the heat.
Thanks for the confirmation.
In this video you can see first how the "farting" happens, and see that it disappears when cool. Distortion is from a pedal, not the amp.
Mat
look at the charts on the datasheet. use your multimeter.
Kit arrived on Saturday, looks excellent. Might be nice to have all electrolytic caps 25v ones though, this would add a few cents to the cost of the parts, but then you'd be able to raise the supply voltage for more power without having to go out and buy some 25v electrolytics. No biggie though.
> raise the supply voltage for more power
It's a "12V" chip. It will stand 16V and a bit more; but you can't arbitrarily jack-up the supply voltage or the chip will blow before a 16V cap does.
Also it's hard enough to heat-sink effectively at 12V-14V. Higher voltage would need heroic sinking, like old VW head castings.
If you are a hot-rodder, you'll take the 80% of a kit that suits you, buy heavy-duty tie-rods or capacitors as you think necessary, and hold the small parts for some other build.
The build document said you can squeeze a bit more power out of it by raising the supply voltage, on page 4. I was thinking of trying this. I started off building effects because I wanted to build an amp as a weekend project, which has been going for about a year now. The Tiny giant is what I have decided to use as the power amp, after a failed attempt at an LM1875 power amp, and before that a 386.
I do have a 1.1k/w heatsink, so excess heat is not much of a problem for me. Anyway, I'll give it a try.
I changed my mind can you guys help me how to make my own power supply for this and regulated already??
Cant find sub or LM388T so that's the last i think would work
Have you tried to get a LT1084 (TO-220 package)?
I spent some minutes looking at the datasheets today, and to me it looks equivalent to LM388T, same pinout and specs. It should be a 1 to 1 replacement.
Mat
Quote from: Rock_on on April 09, 2013, 06:23:35 AM
I changed my mind can you guys help me how to make my own power supply for this and regulated already??
Cant find sub or LM388T so that's the last i think would work
What kind of power supply were you going to use if you had an LM338T?
Voltage out?
Max current out?
Regulated?
I assume DC, but please confirm.
Do you have access to any other power supplies- AC or DC output? If so please list the specs.
This information will help us zero in on a way to figure out how to get you going.
Quote from: Jdansti on April 09, 2013, 12:10:23 PM
Quote from: Rock_on on April 09, 2013, 06:23:35 AM
I changed my mind can you guys help me how to make my own power supply for this and regulated already??
Cant find sub or LM388T so that's the last i think would work
What kind of power supply were you going to use if you had an LM338T?
Voltage out?
Max current out?
Regulated?
I assume DC, but please confirm.
Do you have access to any other power supplies- AC or DC output? If so please list the specs.
This information will help us zero in on a way to figure out how to get you going.
If i have LM338T then i'll just put it in my board and it's done.. I can use non-regulated/regulated now..
Sorry-I guess I screwed up again. When you said you wanted to make your own regulated power supply and asked for help doing that, and you said you couldn't find a substitute for the 338T (which the design calls for), it took this to mean that you couldn't get a 338T and were trying to figure out how to make a supply that would make the amp work without the 338T. That's why I asked you the questions about what kind of supplies you had to work with. So I'm a little confused by your requests and comments, and I don't mean that in an insulting way. You're not my wife are you??? ;D
Either way, I'll step aside and let y'all figure this one out. ;)
Quote from: PRR on April 06, 2013, 12:17:07 AM
Some chips do something like that when over-loaded or over-heated.
Use your finger. (If you can't type afterward, it's too hot.)
Hi Again,
I just installed a heatsink I took from an old computer, and now things are much better. I can now fulfill PRR rule (I can hold my finger on it, and continue playing afterwards), even at max volume. And the "farting" is gone.
Thanks for your help!
I still have to work on some dampening, because being the container a metallic one, there is a lot of rattle that can be mistaken as distortion, but I still can hear some distortion (maybe from speaker) at moderate levels. I will keep on trying.
Mat
Quote from: Jdansti on April 10, 2013, 03:20:05 AM
Sorry-I guess I screwed up again. When you said you wanted to make your own regulated power supply and asked for help doing that, and you said you couldn't find a substitute for the 338T (which the design calls for), it took this to mean that you couldn't get a 338T and were trying to figure out how to make a supply that would make the amp work without the 338T. That's why I asked you the questions about what kind of supplies you had to work with. So I'm a little confused by your requests and comments, and I don't mean that in an insulting way. You're not my wife are you??? ;D
Either way, I'll step aside and let y'all figure this one out. ;)
Ok to clear this up
I just answered your question what would i do if i had lm338T
What kind of supply?? As long it's compatible with the TGA (tiny giant amp) if possible the best voltage for it
Thanks.. Is it clear now? Just tell me
>Thanks.. Is it clear now? Just tell me
Yes
>What kind of supply?? As long it's compatible with the TGA (tiny giant amp)...
It's designed for a laptop power supply.
>...if possible the best voltage for it
15-20 volts DC (closer to 15 is better due to less heat dissipation than higher voltages).
4 amperes or more.
Hi Guys,
I was wondering..... How important is the value of the pot being 10k?
I have now in my TG a linear 10k pot instead of a log one. And of course.... I can only use a portion of its range, most of the change happens at the beginning of the knob rotation.
If I taper it to be more "log", with a 2k resistor, I will have a total resistance of 1.7k. Will this have any side effect in the circuit?
Mat
Now im asking for a regulated (15-20 volts, it's up to you what you think is the best for that range) power supply circuit for the TGA..
I dont want to buy a supply, it's better to make one..
So can you design one please? I cant make one that's why..
It's the LM338T and/or a regulated power supply missing.
Hi Rock on
sorry for stepping in, but I don't get the point of your question. If I understand right, you can't source easily an LM338T, and then you ask how to build your own power supply because of this. Are you aware that in order to build a regulated 12V power supply, you will probably need an LM338T or similar? So... this will not solve your problem, you should concentrate on finding a voltage regulator that can handle the amount of current needed. (like the one I posted some days ago)
Let me explain you how this works:
-LM338T is a voltage regulator. It gets fed with a voltage that can range from 15 to 20 (or more), and delivers 12V (in this circuit. It can be configured for another voltage if needed).
-The circuit of the TG is designed so that this regulation is included, so you just need to find a laptop or similar power supply, and use it.
-If you have already a power supply that gives 12V, capable of delivering 4A, you can skip the LM338T and feed directly the 12V
-If you have to build a power supply,... most probably you will need an LM338T or similar anyway, so I don't see the point in doing this.
Mat
(duplicated)
>I dont want to buy a supply, it's better to make one..
No, when it comes to power supplies and dealing with mains voltages, it's better to buy one. Mains voltages can kill, so although many of us on the forum can answer your question, we won't. It's not that we don't like people who ask how to build power supplies, it's because we don't want them to hurt themselves.
I know how to build power supplies and I've built them. I have some formal electronics training (though I'm not an EE) and know the requirements and hazards. Even so, I normally use a cheap unregulated wall wart that steps the voltage down to a safer level and build off of that. For example, if I need 12VDC, and I have an 18VAC wall wart handy or I find one cheap, then I'll make a circuit to convert it to regulated 12VDC. By doing it this way, I let the manufacturer of the wall wart do the hard part of making sure part of the circuit in contact with the mains voltage is safe. All I have to do is play with the lower voltage side.
BTW, as Potul said, a regulated power supply needs some type of regulator regardless of whether you build the whole thing from scratch or work off of an unregulated wall wart.
Since you asked for a circuit, here's what you'd do. I haven't had a chance to look up the regulator you'd need.
(http://i1160.photobucket.com/albums/q485/jdansti/EE487375-AD94-41D7-B0FC-331F9BAA78D2-5732-000008307F3D3431.jpg)
Ok sorry guys for the inconvenience
I have here 12v dc supply i got from our old vonage..
Its current is not enough and it's not 15 and also i dont know if it's regulated
Can you help me with this??
And if 12v is not enough i assume that i'll do bipolar right??
If it's 12v, I would try to feed it directly to the TG after the regulator and see how it performs in terms of noise.
Unfortunately, it's not an easy task to regulate 12v to 12v, you always need some margin. But there are chances that the 12v PS you have works ok as is.
Mat
If you decide to go with 12V, here's a way to do it: http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg897715#msg897715
Be careful with your Vonage supply. Most 12V models on the web are 1.5A. It might get a little warm!!! :icon_eek: it might become damaged too. It might have an internal fuse or thermal shutoff, but ready to pull the plug. The current draw will increase as the amp's output volume increases.
Hey guys! New here, but been lurking for a while. I'm building the TG,
and was hoping to add a reverb stomp box from BYOC into it. My question
Is in regards to the byoc reverb's negative ground. Do I connect the
- pad on the PCB to the ground on the TG? Will this work or make
Some expensive garbage? The 11.6 out from the TG will be stepped
Down to 5v for the Belton reverb module. I'm planning on using the
max 5053 ( i think its that regulator) which is a step up from the one in
The byoc kit, along with a heat sink on it. My second question: even though
I'm drawing power for the 5v regulator, is it conceivable to power a second
"Stompbox" off the 11.6v out? Like a fuzz face or blues breaker? I'm
Powering this 1-12 combo ("the M.OXIE-Verb 112") with a 16v 4a PS.
Any help would be much appreciated!
Welcome to the forum! :)
What is the voltage requirement for the reverb? Assuming it's 9V, if it were me, I would install a small regulator circuit using a 7809 to bring the laptop power supply down to 9V for the reverb. You could incorporate this on the reverb board the way that the TG has its 12V regulator on the board, or you could make a little board for it.
To answer your question about the ground, you should tie all of the grounds for all of the boards to one point (assuming they're all negative ground) regardless of how you do the power.
Here's an example:
(http://i1160.photobucket.com/albums/q485/jdansti/1E387AED-ED3F-4B9F-A0C2-301E7CA44B57-6896-0000092EDBB22BCC.jpg)
Edit: Bypass and power switches omitted from drawing.
If I'm not mistaken, taking a look at the schematic of the BYOC reverb looks like you can power it directly from 12v as it is. Why do you want to change the regulator?
Mat
^ Good point. I got off track there about powering a generic stompbox that requires 9V.
The TG board has a 12V take off point so you can power other 12V devices. The grounds should all be connected. As you mention, there's no need to replace the LM338T regulator as it's output current is rated at 5A.
Wow,Thanks Guys!
@Jdansti- The requirement for the Belton reverb module is 5v.
@Taylor- The Regulator id be replacing isn't on the TG, its on the PCB for the reverb. Its normally the MC78L05, which may need a bigger heatsink than usual, as in pedal form, the stepdown is from 9v to 5v. I'd be replacing it with the MAX5035, which should easily handle the 12v - 5v with the heatsink available at Small Bear.
@potul- Just want to make sure heat will not be an issue.
I'm placing this mess in a small amp chassis which is much thinner (.04" aluminum) than the typical "stompbox" you guys have been using in lieu of heatsinks, and thus the concern for heat. Maybe i'm worrying over nothing and it'll be fine. But OTOH, Reality has a way of intruding on Designs....
@Jdansti- Thanks for the Ground info! Got confused while elbow-deep in schematics. Yes, the Reverb PCB is Neg GND. Nice mock-up BTW!
Last night after polishing up the schematics i've drawn up, I realized there is a lot of room in the enclosure im using and decided to put in a second effect into it, running off the 12v also. I don't think there'll be an issue as the power supply will put out 4a of current. A simple Dist/OD/Fuzz pedal is what i'm shooting for. Time to cook up some distortion.....
>@Jdansti- The requirement for the Belton reverb module is 5v.
Right. My experience has been that effects that use single PT2399s or the Belton bricks are powered by something higher than 5V, and there's a 7805 or 78L05 onboard to supply 5V to the PT2399 or the brick. I think we're saying the same thing.
>@Taylor- The Regulator id be replacing isn't on the TG, its on the PCB for the reverb. Its normally the MC78L05, which may need a bigger heatsink than usual, as in pedal form, the stepdown is from 9v to 5v. I'd be replacing it with the MAX5035, which should easily handle the 12v - 5v with the heatsink available at Small Bear.
If I may chime in on this one, when I built the Solstice reverb (two PT-2399s), I had problems with the 78L05 and swapped it for a 7805. I found that the 7805 had no problems with: (1) 9V input, (2) powering two PT-2399s, and (3) no heat sink. I think it would have worked with a 12V input because the current draw was so small. I suspect that the BTDR-1 in the BYOC reverb, which has a max current of 100ma, would work fine with a 7805, 9-12V input, and no heat sink. If you did need a heat sink for the 7805, it could be a very smallish DIY custom piece of metal (some small cut up squares from a soft drink can).
Hey guys i foud LM138 and LM238
138 i think can give high current output for a short time only how about the 238??
And btw
Can i use transistor to amplify my vonage PS which has 1.5A if 138 and 238 wont work??
And also use a transistor to regulate??
>138 i think can give high current output for a short time only how about the 238??
LM138/238 Icl = 5A max
PS =4A min
It's cutting it a little close, but just make sure you have a good heat sink on the reg. So you have access to LM138 and LM238, but not LM338? ???
>Can i use transistor to amplify my vonage PS which has 1.5A if 138 and 238 wont work??
No. I think this would defy the laws of physics. Ask everyone you know if they have a PS that says 12VDC/4A or greater. Especially laptop supplies. If the supply is between 12 and 15VDC and >/= 4A you can skip the regulator. If you get one >15A, you should use the regulator.
>And also use a transistor to regulate??
Yes. This usually involves a transistor or two, zener diodes, and a bunch of other components. See: https://www.google.com/search?q=transistor+voltage+regulator+schematic&client=safari&hl=en&tbm=isch&tbo=u&source=univ&sa=X&ei=EIhyUaeAJamO2QXwzIBo&ved=0CDAQsAQ&biw=480&bih=229
> I think we're saying the same thing.
It appears we are.
>problems with the 78L05 and swapped it for a 7805.
>heat sink for the 7805, it could be a very smallish DIY custom piece of metal (some small cut up squares from a soft drink can).
Thanks Jdansti! I will try that. I may actual build the solstice instead of the BYOC kit, I haven't really decided yet. Still working out the kinks.
Am I correct in assuming that the 4A PS should allow for two "pedals" to be added onto the TG?
Input -> Switch 1 -> TG Preamp -> "Fenderish" Tonestack -> Switch 2 -> TG Poweramp -> Output
I I I I
"Ube Reamer" "Reverb"
(https://dl.dropboxusercontent.com/u/967492/TG%20out.jpg)
(https://dl.dropboxusercontent.com/u/967492/TG%20in.jpg)
> Am I correct in assuming that the 4A PS should allow for two "pedals" to be added onto the TG?
You should be fine.
Great build, Rick. :)
Thanks for all the help guys!
Schematics done, just waiting on the pcb to arrive. Its been a little over a week. Should be here soon.
Sweet build man! That cabinet is awesome!!!
Ok thanks!! ^^
I still dont know if we have
138 and 238 i just saw these two when i googled lm338
The shop said their next order would be on june
:(
^ BTW, I noticed in an early posting of you're that you're in the Philippines. You might want to contact jogina111 about where he gets his parts since he lives there too.
O yeah right.. I forgot about that. Thanks!!
I looked at the LM338T datasheet and there I found the schematics but the problem is the transistor values are not specified but the resistor values are specified
Quote from: Rock_on on April 22, 2013, 12:29:14 AM
I looked at the LM338T datasheet and there I found the schematics but the problem is the transistor values are not specified but the resistor values are specified
I'm sorry, but I don't follow what you mean about the "transistor values". The following is an example of how to use the LM338. There are no transitors necessary. This example includes diodes to protect the regulator from capacitor discharges.
(http://i1160.photobucket.com/albums/q485/jdansti/6FEA2D04-EC1A-4881-901F-281956FEEF08-3082-0000036E8FADBFA2.jpg)
Data Sheet: http://www.ti.com/lit/ds/symlink/lm138.pdf
The TGA schematic shows a similar circuit, but without the diodes and with a fixed resistor instead of a pot since you don't need the regulator's output to be variable.
Download the LM338T datasheet
You'll see that there is a page there about the LM338T's inside circuit
Bad english isn't?
Do you mean this?
(http://i1160.photobucket.com/albums/q485/jdansti/23435EB4-EB5D-4497-BC00-6CA611A32E73-3291-000003F80F6C70E2.jpg)
If so, this is an equivalent schematic of what's going on inside of the 338. You have no control over this and you don't need to worry about it. It's there for engineers to understand how the chip operates and to assist them if they want to design circuits that are different from the application examples listed on the data sheet. So unless you need to design something exotic, ignore it!
Yah that's it
What im trying to do now is make my own LM338
Yikes!!! :o
Several comments about this (besides yikes!).
1) The schematic of the 338 "guts" may not show everything going on inside. It may be what's called an 'equivalent circuit'.
2) Even if the guts schematic were perfectly accurate, your chances of building to that schematic and having an operating regulator are about ZERO. I'm not doubting your ability-even the best builders on this forum would have major problems getting something like this to work.
3. It would be easier to use another regulation method such as a smaller regulator circuit based on transistors, or one based on zener diodes.
Edit:
Seriously, PM jogina111 over in the Philippines and ask him how he provided power for his TGA.
Calling Mark/jogina111: please help us out here!
What if i use transformer from an old computer speaker??
220-9v i think the current is 3
Can i use that?? I'll just build my own again..
What ic to use??
What if i use transformer from an old computer speaker??
220-9v i think the current is 3
Can i use that?? I'll just build my own again..
What ic to use??
Hopefully you're talking about a manufactured power supply and not a raw transformer. If so, that would work. You'd have reduced output volume, but it would still be more than loud enough to irritate your entire family and probably the neighbors. ;)
Here's what the data sheet shows for 9V operation:
(http://i1160.photobucket.com/albums/q485/jdansti/DEB8DCC9-9902-4E48-AC39-28C227074814-3389-000004159C658BB8.jpg)
BTW. I'm curious-you can buy the TDA7240 locally, but not the LM338? Correct?
Even jogina knows that..
Hmm im talking about a small square with 4 wires
Even jogina knows that..
Hmm im talking about a small square with 4 wires
Anyone have any exp using the Azabache? I include it in this topic as I'm
Planning on using it in the TG build. I'll be wiring it pre-preamp and using it
As my "channel 2". Any thoughts?
Also, I'm debating on using the Solstice reverb instead of the BYOC reverb2
Any solstice uses out there?
It's really a toss-up between the Azabache and Ube Reamer, as well as
Between the Reverb2 and the Solstice. They all seem to sound good....
Quote from: Rock_on on April 22, 2013, 11:24:54 AM
Even jogina knows that..
Hmm im talking about a small square with 4 wires
If it looks like anything in the picture below, the answer is no.
(http://i1160.photobucket.com/albums/q485/jdansti/8A96DF73-F61C-43AF-879E-B11F3F99466D-4365-000004E06568C7E9.jpg)
If you're thinking of making your own power supply connected to the mains power, I gave you my opinion on page 33 when you asked the same question. http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg906387#msg906387
An Internet forum is not the place for a novice to learn about working with mains voltages. If making a supply for a guitar amp is worth risking your life, you should seriously think about dropping the guitar and learning drums. ;)
Here's what I did to my TG amp, and I'm more than happy I've done these.
-used a bigger speaker instead of getting a PSU with more current.Since turning the volume pot to max makes it fuzzy.
-build it as it is and use effects pedals. Adding preamp or channels would induce noise and hum. I Skipped the regulator chip and using a 12v 2A PSU yet I'm getting a monstrous sound from this amp..
@Jogina - What about tone stack? I definitely need a T/M/B on this amp.
The point of the build for me is to make a fully functional amp that requires little in front of it. I plan on using it to play out in some coffee house /jazz club-type environments where i dont need blistering sound, but would want at least a "lead" channel,and of course, reverb is a must.
Is there any way to build the pedals inside an enclosure with the TG and eliminate hum? I think I could do with using a pedal for the "lead" channel (though it may be mounted to the cabinet in a separate enclosure to utilize a "kick-switch" that protrudes from the side of the amp and powered off a 9v out from the TG board), but I kinda feel like having a built in reverb should be easily done and would be a very welcome member to the amp's population. Its going to be in a smallish cabinet that houses a Celestion G12T-75, 12" @ 4 Ohms, but built with a chassis that houses everything in such a way as to be removable from the cab and used as a "head" in the event that I hate the speaker, cabinet, or both.
Its basically the same, i've done this before but I like switching effects with my foot instead of switching them on from the amp interface. It's basically the same using different power supplies for the TG and for the effects but they.'Re on the same cavity.. With the power supplies also inside
Its basically the same, i've done this before but I like switching effects with my foot instead of switching them on from the amp interface. It's basically the same using different power supplies for the TG and for the effects but they.'Re on the same cavity.. With the power supplies also inside. For the tone stack, maybe the preamp stage for the tiny giant can drive a TMB tonestack. Or maybe build a tone mender from runoffgroove.. Sorry for double posting.. I'm just using my phone to post cause I'm outdoors miles away from my PC..
How voltge multiplier? I have 9V tp link psu.
Can i use multiplier to make an 18V psu?
Oh nevermind i remeber now, the current is not enough. Sorry
What you actually need is a 12v PSU 2amperes or greater..Thats not very hard to get in the philippines..
So I've finally decided on the scheme. I went with just a tone stack and a reverb. I used a modified fender control scheme,
With 270pf, .022mf, and .15mf caps and a 4k7 resistor. I've included a DPDT switch for the reverb, and it has 2- b50k pots.
I used an A25K for Treb and Bass, and an A5K for middle. I also got an A50K for the master volume pot. Each is modular,
So if something's not quite right i can pop it out by sections. Wired up everything i could on perfboard. Still waiting on the
TG PCB though. I plan on building the ROG Azabache and the Ube Reamer as stand-alones. The speaker i got is a celestion
G12-75 (i think) i got it off Fleabay and am still waiting for it to arrive.
Not really a building question, but was curious:
For those that ordered the PCB/kit from Taylor, whats turn around like on shipping? Can't wait to get this!
Sent my payment on 4/12, haven't recieved it as of 4/24, so maybe like 2 weeks?
Hopefully it'll be here soon!
Quote from: Moxienator on April 24, 2013, 07:55:39 PM
So I've finally decided on the scheme. I went with just a tone stack and a reverb. I used a modified fender control scheme,
With 270pf, .022mf, and .15mf caps and a 4k7 resistor. I've included a DPDT switch for the reverb, and it has 2- b50k pots.
I used an A25K for Treb and Bass, and an A5K for middle. I also got an A50K for the master volume pot. Each is modular,
So if something's not quite right i can pop it out by sections. Wired up everything i could on perfboard. Still waiting on the
TG PCB though. I plan on building the ROG Azabache and the Ube Reamer as stand-alones. The speaker i got is a celestion
G12-75 (i think) i got it off Fleabay and am still waiting for it to arrive.
let me know how your tonestack project go. Its pretty interesting for me. How would you connect it to the TG?
Quote from: Moxienator on April 24, 2013, 09:49:37 PM
Sent my payment on 4/12, haven't recieved it as of 4/24, so maybe like 2 weeks?
Hopefully it'll be here soon!
OK, ordered mine on 4/15. Just itching to start!
@jogina- i have it rigged up on perf board right now. The input of the tone stack comes
From U1A via the volume pots' lug #1 pad on the TG. The signal can be switched to then go
Either directly to the volume pot lug#1, or through the reverb pedal that is built in and then to
The volume pot.
I was thinking of adding the Lead channel using an ROG Azabache, but from everyone's advice
And the added complexity of the controls, i decided to leave it out and stick with just the 'verb.
@Somicide- i know exactly how you feel!
Nice!!! \m/ i found 26v AC PSU 4 or 3 amp!!
♪(*^^)o∀*∀o(^^*)♪ cheers!!
How to lower it?
Edit:
I mean what Ic regulator?
Good! You're getting closer. Now you need to rectify it to DC, smooth out the ripple, and drop/regulate the voltage.
For the rectification, you'll need 4 diodes. They can be any of the following: 1N4003, 1N4004, 1N4005, 1N4006, 1N4007.
Then you'll need a capacitor to smooth out the AC. This can be 470μF - 1000 μF.
Now the hard part. You'll need a regulator. It can be a fixed output or adjustable. If you can't find an LM338, try looking for an LM1084-12 or LM1084-ADJ. See the drawings below for using these.
(http://i1160.photobucket.com/albums/q485/jdansti/8C41FD09-1996-4CE7-B987-6EE9555BCBB9-7774-00000929192967B7.jpg)
If you can't find a regulator, an automotive regulator might work, but I'm not sure about how to connect it. I believe that these have an extra contact that goes to a relay inside so that it's only active when the alternator has output. Maybe someone can help you with that if its your only option.
But what i have is 26 not 24
Will it work? I mean the IC.
Sorry-Yes, 26vac will work fine
BTW-If you happen to have access to a 12V battery for a small vehicle such as a motorcycle, scooter, golf cart, etc., that would work too as long as you have a way to charge it. The amp would use very little juice compared to the battery capacity, so you wouldn't have to recharge it that often. If a friend has a charger or if you buy a small cheap charger, that would be another option. Kinda bulky, but it would work. Just recharge it when it gets down below 11V. If you did this, you could omit the regulator on the TGA board.
Other options:
*The output of a cheap 2A battery charger might work if you cleaned it up with some filtering capacitors. No batteries required.
* Not as economical in the long run as a lead-acid battery mentioned above, but you could power if off of eight to ten D cell batteries connected in series to get 12V-15V. I'm not sure how long they would last, but they have higher capacity than 9v batteries.
*Rechargeable D cell alkaline or NiCads.
*Two 6V or one 12V lantern batteries.
golf cart?! what kinda world do you live in?! hang on - i'll just pop over in my personal jet to see for myself... :P
Quote from: Jdansti on April 26, 2013, 12:43:53 PM
BTW-If you happen to have access to a 12V battery for a small vehicle such as a motorcycle, scooter, golf cart, etc.,
Sounds reasonable to me.
Quote from: artifus on April 26, 2013, 12:50:55 PM
golf cart?! what kinda world do you live in?! hang on - i'll just pop over in my personal jet to see for myself... :P
Ummm... Not sure how to answer that, but I'll try. I take it you've never had the amazing experience of riding in one of the most luxurious machines every conceived in this universe or any other. The
golf cart.
I wasn't suggesting he go out and buy one of these comfortable, costly, deluxe, elaborate epicurean, extravagant, fancy, fit for a king or queen, grandiose, gratifying, hedonistic, immoderate, imposing, impressive, lavish, lush, magnificent, majestic, opulent, ostentatious, palatial, pleasurable, plush, posh, pretentious, ritzy, sensual, sensuous, splendid, stately, sumptuous, sybaritic, upscale, and well-appointed vehicles. All he would have to do is look for a man wearing an ascot and spats, club him over the head, and search the area within a 50-ft radius of the ascottted/spatted/evil/rich guy's body, and surely there will be one of these golf carts that has a battery for the taking. That's all I'm saying.
BTW-please try to limit your personal jet poppings. It's bad for the environment. ;)
icarus was solar powered
Got my TG kit today! Thanks Taylor!
After looking over the board for a bit, I came to the unfortunate conclusion that either the lm338 or the tda7240 can have a heat sink, not both. The board is just too small to accomodate both finned heatsinks. I'm thinking that I'll sink the LM338 with the fins and attach it to the chassis, and the TDA7240 will be attached to the chassis only, with no finned heatsink. Good/Bad?
Second thing- what are the two connection points that are near pin 1 of the TL072 that will be under the socket? one of them has an L next to it. It looks like it comes off the signal input. Do I connect these anywhere??
Taylor- Great job! Love the board! just wish it had enough room for the heatsinks.
I guess there are 4 unconnected turrets, not counting the 12v out. Should there be jumpers? Or do they really not connect to anything?
Quote from: Moxienator on April 27, 2013, 01:49:01 PM
After looking over the board for a bit, I came to the unfortunate conclusion that either the lm338 or the tda7240 can have a heat sink, not both. The board is just too small to accomodate both finned heatsinks. I'm thinking that I'll sink the LM338 with the fins and attach it to the chassis, and the TDA7240 will be attached to the chassis only, with no finned heatsink. Good/Bad?
You should be able to mount both to the enclosure, though be careful that you electrically insulate the LM338 (its tab
isn't ground).
Quote from: Moxienator on April 27, 2013, 01:49:01 PM
Second thing- what are the two connection points that are near pin 1 of the TL072 that will be under the socket? one of them has an L next to it. It looks like it comes off the signal input. Do I connect these anywhere??
I guess there are 4 unconnected turrets, not counting the 12v out. Should there be jumpers? Or do they really not connect to anything?
The "L" under the TL072 is actually a rectangular tab indicator showing the direction of the IC. My guess is that you don't need to do anything with the unmarked pads. Taylor or one if the others who have built it should be able to let you know.
The unmarked things that look like pads are called vias. The board is double sided, meaning it has traces on both sides, the vias make connections between traces on the front and back, you don't do anything with them.
Quote from: Moxienator on April 27, 2013, 01:49:01 PM
Got my TG kit today! Thanks Taylor!
After looking over the board for a bit, I came to the unfortunate conclusion that either the lm338 or the tda7240 can have a heat sink, not both. The board is just too small to accomodate both finned heatsinks. I'm thinking that I'll sink the LM338 with the fins and attach it to the chassis, and the TDA7240 will be attached to the chassis only, with no finned heatsink. Good/Bad?
Second thing- what are the two connection points that are near pin 1 of the TL072 that will be under the socket? one of them has an L next to it. It looks like it comes off the signal input. Do I connect these anywhere??
Taylor- Great job! Love the board! just wish it had enough room for the heatsinks.
I guess there are 4 unconnected turrets, not counting the 12v out. Should there be jumpers? Or do they really not connect to anything?
Looks like mine should be just around the corner, then! Anxiously awaiting.
@ bluebunny, Jdansti, & Slacker - Thanks guys! Great Info!
I got it wired up, but I think I fried the board. I tried using sockets for the LM338 and TDA, but then they wouldn't stay in them, so I had to take the sockets out. In doing so, one of the turrets on the TDA sort of separated from the board. Hopefully it works, I'll be getting another just in case from taylor soon.
@ Somicide - Yeah, it actually ships quickly, I think he was just waiting for more to come in or something. Once I got the confirmation email, it came like two days later.
I decided to throw a finned heatsink on the LM338 (electrically isolated with the washer and the rubber pad) and insulate its legs, the TDA will have a steel washer attached to it for spacing and both will be mounted to a 4" x 1.25" x 0.25" brass bar as an additional sink, and then mounted to the enclosure. The metal of the enclosure is thin, as its more like a "thin-panel amp chassis" than a stompbox. Even though it's large (12" x 3" x 2.2" ), its very thin (.04" I think), so I'm hoping that the extra precautions will keep everything cool.
Whats the story on the Volume control? Has anyone used a larger Pot on it? I scaled down my tone stack to use 25K pots for treble and bass, and a 5K (should be 1k) pot for the mid control. I now sort of understand how it is usually done - halve the resistors, double the capacitors - which is not how I originally did it, so new parts are on the way again.
With this in mind, can I use a 50K volume control without any ill effects? Or should I stick to the 10k?
I think this question may have been answered before but I haven't been able to find it in this thread.
There are 2 point on the PCB under TL072. Do I need to do anything with these or just leave them alone?
Quote from: MDK002 on April 29, 2013, 07:04:49 PM
I think this question may have been answered before but I haven't been able to find it in this thread.
There are 2 point on the PCB under TL072. Do I need to do anything with these or just leave them alone?
http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg909263#msg909263. ;D
Quote from: bluebunny on April 28, 2013, 11:41:56 AM
You should be able to mount both to the enclosure, though be careful that you electrically insulate the LM338 (its tab isn't ground).
Could you use electrical tape for this? E.g. sticking it on the back of the LM338 and then sticking it against the enclosure?
Quote from: Valoosj on April 30, 2013, 01:49:34 PM
Quote from: bluebunny on April 28, 2013, 11:41:56 AM
You should be able to mount both to the enclosure, though be careful that you electrically insulate the LM338 (its tab isn't ground).
Could you use electrical tape for this? E.g. sticking it on the back of the LM338 and then sticking it against the enclosure?
I guess that depends on how hot the LM338 gets and at what point the tape prefers to catch fire. :icon_biggrin: I'd tend to go for a pukka mica or silicone insulator (or whatever they're made of...).
A what now? :-\
If you buy Taylor's kit it comes with isolating pads and washers for both chips.
Quote from: Valoosj on May 01, 2013, 05:36:40 AM
A what now? :-\
Sorry, "pukka" = "genuine, real" ...
Do what slacker said, and you're sorted.
Quote from: bluebunny on May 01, 2013, 04:07:47 PM
Sorry, "pukka" = "genuine, real" ...
Do what slacker said, and you're sorted.
Ah yes, I should have known. Heard Jamie Oliver say it over and over again :icon_lol:
I've bought the components I need and I always etch my own pcbs, so I need to find a different solution, or find out exactly where Taylor gets his washers (or similar ones).
Got here yesterday. I've gotta say, the pictures don't really convey just HOW small this beauty is! Waiting til this weekend to cook up a mother's day gift with one, and a self-purchased father's day gift with the other. Need to grab a unibit too. This is awesome; thanks Taylor!
Thanks!
Yorick, I just get them on ebay. Search for "to-220 spacer" and/or bushing and you should find them.
Thanks Taylor!
Well, I finally got around to building this over the weekend. Nice board, Taylor.
I have to say it's very quiet. Very quiet indeed. Like, totally silent! :D
:icon_sad:
So here goes with the debug... I'm getting a healthy 11.69V out of the LM338. This is being delivered correctly to the TL072 and TDA7240A, and both are grounded OK. There's no tricky continuity between the LM338 tab and ground, nor to either speaker connection. The volume control does indeed sweep to ground in one direction, and away from it in the other. The standby switch does indeed do its job grounding pin 2. So far, so good.
The next bit seems a little off, though. Whilst the unused half of the TL072 is producing half the positive rail (5.84V) as you might expect, the voltage divider made up of the two 1M resistors is not. They have 3.9V between them (which is then the bias going into pin 5 of the TL072). I would have put money on closer to 5.84V. Anyway, looks like the TL072 is working, despite the strange bias. But the TDA7240A is perhaps looking suspect? ???
Apart from power and ground at pins 6 and 4 (and 2 when the mute switch is thrown), I'm getting 0V at pins 5 and 7 (the speaker outputs) and 0V at pin 3 (the input). Pins 1 and 2 (with the mute open) look like they're discharging slowly through their capacitors to ground.
Other than that, there's no smoke, no heat, no emergency services on their way. Any thoughts?
I guess the next step for me is to see if and where there's any signal... :-\
Shall we assume that you've checked that your guitar's volume is turned up and you have a good cable? :)
You ready know the stuff I'm about to say, but sometimes it helps to review it:
-Check the signal and ground connections on the input jack
-Check cap values and polarities
-Check resistor values
-Check that TL072 isn't backwards
-Check for cold solder joints and bridges
-Check that the speaker works
Also, shouldn't you be getting around 14V from the LM338 instead of 12V given the resistor values selected by Taylor? The amp would still run on 12V, but I wonder if this is pointing to the problem.
Ha ha! Yes John, guitar turned up... :D
OK, nice jangly guitar getting all the way to pin 3 of the TDA7240A (i.e. the input). Absolutely nothing at the output pins (tried the audio probe across the speaker jack). Speaker is working. All component values and polarities checked.
Have I scored a bum 7240 off eBay??
P.S. The one good thing to come out of this is that the audio probe I built a few weeks ago works like a dream! :icon_rolleyes:
Quote from: Jdansti on May 07, 2013, 03:32:40 PM
Also, shouldn't you be getting around 14V from the LM338 instead of 12V given the resistor values selected by Taylor? The amp would still run on 12V, but I wonder if this is pointing to the problem.
Taylor's build docs say 11.6V, so I was quite chuffed with my 11.69V! :icon_biggrin:
Sorry! :icon_redface: Missed that and the paragraph about changing the resistors to get more power. I just saw the note on the board photo about the 14V take off for other external things.
I guess it's possible you got a bad amp chip. One option would be to carefully remove the 7240 from the PCB, breadboard it with the minimum components shown on the data sheet, and see what happens.
> voltage divider made up of the two 1M resistors is not. They have 3.9V
A 1Meg||1Meg= 500K divider is a HIGH impedance. What kind of meter do you use?
A good VTVM or typical DMM is usually 10Meg input, which will cause a 5% loading-error on a 500K source.
Needle-meters, and some specialty DMMs, have lower input impedances.
In either case, in this circuit, poking the output of the opamp should give the true divider voltage (since the amp is wired for unity-gain at DC, and the opamp output is plenty strong).
Futher obvious check: the output of a POWER stage has to be halfway between the supply rails. With 12V supply you really want to find 5V to 7V at the output. This design uses a Bridged output, really two outputs; both should be very similar to each other and awful close to 6V.
This chip has a feature: if an output is shorted to ground (got the car-speaker wire pinched in bodywork) both chanels will shut-down nicely. (Older designs would spark the wire until something burned.)
> I'm getting 0V at pins 5 and 7 (the speaker outputs)
Disconnect the PCB from your wiring. Now what's the volts? Study the PCB for blobs. Temporarily unsolder the 0.1u(?) output loading caps (in case they shorted). Assuming a good chip, it's got to be a short on an output.
I hope you noticed that the speaker jack may NOT be grounded (no metal jack; or fiber washers).
> Have I scored a bum 7240 off eBay??
Odds may be 50:50. Is there a reputable supplier?
Quote from: PRR on May 08, 2013, 12:59:19 AM
> voltage divider made up of the two 1M resistors is not. They have 3.9V
A 1Meg||1Meg= 500K divider is a HIGH impedance. What kind of meter do you use?
A good VTVM or typical DMM is usually 10Meg input, which will cause a 5% loading-error on a 500K source.
I'm using a DMM, nothing special. I'm less bothered by this reading now (though still interested why it's apparently "low"), since I'm getting a good signal either side of the TL072 buffer (and the output is pretty much mid-rail).
Quote
Futher obvious check: the output of a POWER stage has to be halfway between the supply rails. With 12V supply you really want to find 5V to 7V at the output. This design uses a Bridged output, really two outputs; both should be very similar to each other and awful close to 6V.
This chip has a feature: if an output is shorted to ground (got the car-speaker wire pinched in bodywork) both chanels will shut-down nicely. (Older designs would spark the wire until something burned.)
> I'm getting 0V at pins 5 and 7 (the speaker outputs)
Disconnect the PCB from your wiring. Now what's the volts? Study the PCB for blobs. Temporarily unsolder the 0.1u(?) output loading caps (in case they shorted). Assuming a good chip, it's got to be a short on an output.
Hmmm... yeah, both outputs are "zero" wrt ground, but apparently have no
continuity to ground. I'll recheck carefully when I get home. PCB work looks neat enough, but it doesn't hurt to take another close look.
Quote
I hope you noticed that the speaker jack may NOT be grounded (no metal jack; or fiber washers).
Yep! :) Speaker jack connected to nothing but the output pins.
Quote
> Have I scored a bum 7240 off eBay??
Odds may be 50:50. Is there a reputable supplier?
I may find out soon. Found another from a
local vendor this time. Will try a substitution when that arrives.
Thanks for your input, Paul. John too. Will get this sorted: it's too neat a little project to let go.
Quote from: PRR on May 08, 2013, 12:59:19 AM
> Have I scored a bum 7240 off eBay??
Odds may be 50:50. Is there a reputable supplier?
Looks like I found one of each! I swapped out what turned out to be a rogue amp chip. The new one works like a dream - sensible voltages, gets warm, and lots of nice, loud guitar coming out of it. Just tried it with my BSIAB2 and most likely upset the nieghbours. :icon_eek:
Thanks for your help, guys. This is a neat project - thanks, Taylor. Sounds great. Everyone should build one! ;D
Glad you got it working! :)
Quote from: Jdansti on May 11, 2013, 03:30:27 PM
Glad you got it working! :)
Me too! Thanks John. :D
Very exciting when it finally fires up and gets so much louder than you're expecting, eh? :)
Quote from: Taylor on May 11, 2013, 05:16:56 PM
Very exciting when it finally fires up and gets so much louder than you're expecting, eh? :)
Oh yes. :icon_twisted:
Hi, just powered up my tiny giant today and i'm having an issue. When I turn it on, there is a rhythmic popping sound. When I play something on the guitar, the sound goes away mostly.
Also, when I turn the volume up more than about 2/3 the sound really breaks up and distorts to the point it's horrible.
I've checked for grounding issues. No problem there that I can find.
power supply is rated 16V -- 4.5A
10K pot
built it exactly as noted on the build sheet.
Where should I start looking for problems?
thanks,
a little more info on the popping sound. with the volume turned all the way down....popping is faster. turn the volume to 3/4 and it just about stops... turn up all the way and it pops a little faster. the popping sound is pretty much the same volume all the time. now when i play the guitar it just keeps popping.
Also, the standby switch has no effect on the amp...sound comes out in either on or off position
Can you provide voltages on all of the pins of the ICs and regulator? Place your black probe on a ground point and use the red probe to check the components.
Hi John...thanks for helping
TL072
pin 1 5.84
pin 2 5.85
pin 3 5.57
pin 4 0
pin 5 5.57
pin 6 5.84
pin 7 5.85
pin 8 11.75
LM338
16.5 v in
11.81 v out
10.56 adj
TDA7240
pin 1 9.3
pin 2 11.9
pin 3 9.06
pin 4 0
pin 5 8.17
pin 6 0
pin 7 8.70
^ Pin 6 of the TDA7240 is supposed to have power on it and you're showing 0v.
Are you using the board from MusicPCB, or some other board or perf?
I'm using the board and components from Music PCB.
Here's a long shot guess.
You have power on pin 2 but not pin 6. Both of these pins are two from the end. Could you have counted from the wrong side while checking the voltage?
(http://i1160.photobucket.com/albums/q485/jdansti/3034E78F-7DE3-4652-8813-08325F509C4E-9948-00000B2F2C7172C7.jpg)
you are correct....i had them reversed.
TDA7240
pin 7 9.3
pin 6 11.9
pin 5 9.06
pin 4 0
pin 3 8.17
pin 2 0
pin 1 8.70
Ok. Well that's good news and bad news. I'm not an expert on this, but your voltages look fine.
Have you made sure neither terminal on your speaker is connected to ground?
If that's ok, then it looks like its photo time. Can you get some clear shots of both sides of the board and the off-board connections?
neither is connected to ground.
i'll take a few photos and post shortly
(http://i1334.photobucket.com/albums/w649/MKnoxPhoto/2e1ec7df-5dd7-4918-847d-e02053299b68_zpse8a7910f.jpg)
(http://i1334.photobucket.com/albums/w649/MKnoxPhoto/57b51655-a854-4b1b-bf83-d4e48f38fc5b_zpse18e2a41.jpg)
Here's a couple of photos of the off-board wiring...not sure how much these will help.
(http://i1334.photobucket.com/albums/w649/MKnoxPhoto/66f9e3f6-649e-40e7-8e0d-568c5aaf9a19_zpsda8660ae.jpg)
(http://i1334.photobucket.com/albums/w649/MKnoxPhoto/image-3_zps86c1b521.jpeg)
Is this your speaker jack?
(http://i1160.photobucket.com/albums/q485/jdansti/9F31EC5D-AA9C-42EB-B1E3-352D7C18E811-10095-00000B5CCABED9A7.jpg)
You said that neither speaker wire was grounded, but I have to ask, if this is your speaker jack, do the metallic parts which are in contact with the enclosure have continuity with either of the jack's terminals? You might want to check this with your DVM.
That is not the speaker jack. That's the hardware for the power-on LED. It has thick rubber grommets between the LED, wiring and the hardware. No grounding issue there.
It was originally meant to house a lamp, but I removed the base for the bulb and replaced it with grommets to accommodate the LED.
top picture....left to right... instrument input, standby switch, volume pot, LED (power-on), on-off switch
bottom picture....left to right... power jack, speaker jack.
Ok-thanks.
What are the wires with the arrow pointing to them below connected to?
(http://i1160.photobucket.com/albums/q485/jdansti/71A431BF-DE99-47A8-98EF-B2B8995ACFCC-10448-00000C2A3550B72D.jpg)
those wires just loop back around to the input jack....cannot really see that from the photo
Thanks. Well for now, I'm stumped. Your wiring and soldering look great.
I was wondering how the two heat sinks are being held in contact with the chips. I don't see any screws, so is the white stuff a heat-conductive adhesive of some kind? The reason I ask is that if the TDA7240 gets too hot, it could make some noise. Can you hold your finger on it without experiencing pain?
The speaker output pins voltages seem high, and the only other thing that I can think of at this time is tha the TDA7240 might be bad. I've seen at least one other post where someone had a bad chip, although he was getting 0V on the output pins: http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg910767#msg910767
Maybe Taylor or someone else can help us out.
the heatsinks are made for RAM modules....i just used the adhesive that came with them.
no heat to speak of from TDA7240. the problem starts as soon as i turn the switch on.
i'm stumped too....my guess was that either the TL072 or the TDA7240 were bad....or both? I don't have any spares of these 2 on hand or I'd swap them out.
I did see where someone else had a bad chip but I could not find any other problem in the forum like i'm having.
I appreciate you looking at this. Maybe someone else will have some ideas.
So, I plugged in a different guitar....popping sound not so prominent today but it's still there. the TDA7240 is getting pretty hot real fast. wouldn't want to keep my finger on it...this only after playing about 10 seconds or so.
the sound is clipping really bad too...can't hardly turn the volume up past about 1/3 unless i play VERY gently.
You have your guitar input wires running with your speaker jack wires. They really must be SEPARATED.
Those heatsinks are much too small for a 20-Watt amplifier. Since you glued them, a fan may help; though it might have to be a LOUD fan to focus huge air on those small sinks.
Is that a key cabinet?
Hi Paul. I was wondering if the wiring should be separated. no problem to move things around.
i can replace the heat sinks with something more substantial.. i'll make sure it's isolated from the chips and doesn't ground them. I have a handful of those copper heat sinks....maybe i can come up with a way to mount more them on some aluminum sheet and attache to the chips....we'll see.
and yes....that is a key cabinet :icon_biggrin: i'm building a case to go around it so it will look like a small amp head....once i work out the bugs.
I'll update as soon as i get things moved around... I'll post more pics as i get closer to finishing the cabinet.
thanks for all the help.....i'll let you know how it works out.
>You have your guitar input wires running with your speaker jack wires. They really must be SEPARATED.
Good catch, Paul! I didn't even consider that. I'll store that fact in my little brain!
Quote from: MDK002 on June 07, 2013, 11:33:52 PM
i can replace the heat sinks with something more substantial..
Just rearrange things so you can bolt the two chip tabs directly to your enclosure (with a mica washer to insulate the regulator). With the size of box you have, it won't even come close to breaking into a sweat. I have mine in a small extruded aluminium case and it's barely ever above room temperature.
ok... I separated the input and speaker wires from each other....just moved them around inside the chassis. problem is still there. sounds like a heartbeat almost.
when the volume is increased, it clips on each "heartbeat" and also when a note is played with any force.
I only had the amp on for about 10 or 15 seconds total...the problem started as soon as I turned on the amp.
would shortening the input and out put wires make any difference? There is some extra length there that is not needed. Also, I can't figure out why the standby switch has no effect.
I'm going to work on getting the heat sink issue fixed.
Any other ideas?
I wouldn't short the output. Even if it were safe to do so, it's not a good diagnostic technique because you would expect your speakers to be silent if you did this.
The next step that I would do is build a simple audio probe and follow the signal starting at the TGA input. See: http://www.diystompboxes.com/pedals/debug.html The only deviation from the instructions would be to stop probing after you check the input of the TDA7240. No need to probe the output of the chip and it could potentially damage whatever you have the audio probe connected to.
One other thought. You might have already said, but have you checked that the speaker works with a trusted amp?
I have checked the speakers....I've used 2 different cabinets that work great with my other amps.
I'm going to put together an audio probe and start looking for the problem. I'll take the time to clean up the wiring to make it fit the chassis better.
Might be a week or so but I'll post my findings as soon as I can. Lot's of other projects on my honey-do list. ;D
Quote from: MDK002 on June 09, 2013, 11:15:26 AM
Lot's of other projects on my honey-do list. ;D
I know the feeling! :(
John, thanks so much for helping folks debug in this thread. Most of the time you've helped somebody before I even see their question.
I enjoy solving mysteries (or at least trying to)!
I remember what the owner of a hobby shop told me when I bought my first RC airplane kit. He said to make sure I get help from him or someone knowledgable, because if the plane doesn't fly, or if I crash it on the first flight, I'll be less likely to continue the hobby.
Hi,
Trying to finish off my, Tiny Giant Combo..
Question: I will add the line describe mod as described here http://i.imgur.com/Uill1.gif
Is it really correct to add a 10k resistor in series after the 10k volume pot? Wouldn't it decrease the signal very much?
Or did I get something wrong?
Edit: I put it together now and it works ok, both the guitar and line in amplification.. :)
Regards,
Jakob
Hey guys it's me again
I dont know if i asked this one before but
What if i have a preamp already (jokerx's blackforest, or jcm2000).... Do i need to remove the stock? Or stack it?? I mean just put my preamp in my pedal board..
Quote from: Jdansti on June 08, 2013, 10:25:27 PM
I wouldn't short the output. Even if it were safe to do so, it's not a good diagnostic technique because you would expect your speakers to be silent if you did this.
The next step that I would do is build a simple audio probe and follow the signal starting at the TGA input. See: http://www.diystompboxes.com/pedals/debug.html The only deviation from the instructions would be to stop probing after you check the input of the TDA7240. No need to probe the output of the chip and it could potentially damage whatever you have the audio probe connected to.
Alright, I've got good news. After probing the circuit I found that the TDA7240 was the problem. I have replaced it and the amp is now functioning properly. And it's mighty loud for it's size.
Paul, I took your advice and removed the puny little heat sinks and dug up a very chunky piece of aluminum from my pile of stuff I've collected over the years. I've got it bent into shape and will have it attached to the chips as soon as my little bushings get here from China. I'll post some photos once I have it together.
I'm building a cabinet for it to match my Marshall 4x12.
John and Paul, thanks for your help...and everyone else that posts on here to help us beginners out. You guys make this enjoyable.
Quote from: Rock_on on June 15, 2013, 07:40:31 AM
Hey guys it's me again
I dont know if i asked this one before but
What if i have a preamp already (jokerx's blackforest, or jcm2000).... Do i need to remove the stock? Or stack it?? I mean just put my preamp in my pedal board..
You can leave the stock preamp; it's totally clean so there should be no issue stacking them. Just watch the levels going into the TG preamp as it's not the most thrilling sound when the opamp is overdriven.
I prefer removing the stock preamp and rebuilding the poweramp from the 7240 datasheet... I have made an amp using a wampler plexidrive to the tda 7240 and I'm keeping it to myself. Love how it sounds...
Hi,
Finally ready with my Tiny Giant Combo. Some pictures and spec:
Tiny giant - standard PCB etc
Power feeding: HP laptop charger, 18V / 3.5 A
Speaker element: Faital Pro 4Fe35
Nominal Impedance: 8 Ohm
AES Power Handling: 30 W
Maximum Power Handling: 60 W
Sensitivity (1W/1m): 91 dB
Frequency Range: 90-20000 Hz
Speaker cabinet:
Birch plywood 14 mm
Outer size:
Height: 220 mm
Width: 120 mm
Depth: 95 mm
Volume 1,77 litres
Bass port: diameter 24 mm, length: 42 mm
Additional features:
- 9 V output (for pedals etc)
- Line in
(http://imageshack.us/a/img20/6186/c2fp.jpg)
(http://imageshack.us/a/img27/6916/ajk1.jpg)
(http://imageshack.us/a/img543/4517/xayl.jpg)
Hi again,
My Tiny Giant Combo sounds quite good, but it has some distortion. Not so much at lower levels byt when volume is at 11-12 o clock, its quite bad. Especially since I'm after a clean tone. When I play through a larger cabinet (10" Eminence speaker), it's mucher better.
How come the sound gets distorted with the small speaker (the 4", as describer in earlier post..)
Here are som sound clips at different volume levels. (The is recording as such is not generating any clipping)
I used a Les Paul, neck pickup, full volume.
Youtube clip: http://youtu.be/Q3Ux4wj8sHE
Comments and advice welcome.
The sensitivity of your 4" speaker is a lot lower and therefore it doesn't get as loud at the same low settings on the knob. It's true that this amp will distort at higher volumes. To get more clean headroom a higher-sensitivity speaker is needed.
There is a loose rule in speaker design that you can have two of the following, but not all three: low (frequency response), loud, and small.
Hi Taylor,
I think I see what you mean. So to improve this set up I either need
1) a speaker with higher sensitivity. But I think it's difficult to find a 4" with at least some response below 100Hz with higher sensitivity than 91 dB(?)
2) Use a more powerful amplifier. But then it would be a more complex design I suppose, with large transformer etc. Or is there any similar (=simple) amplifier to Tiny Giant with say 60-80 watt?
Regards,
Jakob
Quote from: Taylor on June 16, 2013, 11:22:31 AM
The sensitivity of your 4" speaker is a lot lower and therefore it doesn't get as loud at the same low settings on the knob. It's true that this amp will distort at higher volumes. To get more clean headroom a higher-sensitivity speaker is needed.
There is a loose rule in speaker design that you can have two of the following, but not all three: low (frequency response), loud, and small.
Having thought a little bit more.. It seems like the amplifier distorts more at say 11oclock with the small speaker compared to the larger one. (irrespective of the dB output from the speaker). Does it make sense? If so, why?
Regards,
Jakob
Quote from: Taylor on June 16, 2013, 11:22:31 AM
There is a loose rule in women that you can have two of the following, but not all three: ...
Fixed it for you :icon_mrgreen:
(And fill in the dots for yourself. We all know how it goes)
Quote from: Valoosj on June 16, 2013, 02:48:04 PM
Quote from: Taylor on June 16, 2013, 11:22:31 AM
There is a rule in loose women that you can have two of the following, but not all three: ...
Fixed it for you :icon_mrgreen: :icon_mrgreen:
> to improve this set up I either need
A 4-inch just can't make room-filling power.
I have a 4-inch speakered amp but it is only 1 Watt and was probably $12.95 when new.
The TG is *not* a "tiny amplifier". It makes 10 or 20 Watts. Much more than a Champ, more than a Princeton or DeLuxe. Not a whole lot less than amplifiers sold with two-10 even two-12 speaker systems. (I had an 18W with four 10s, lovely amp.)
10-20 Watts is a LOT for just 3 inches of air-paddle with any bass.
While the speaker specs may say "30 Watts!", that's a melt-down rating. The coil won't burn from electrical heat, even though the cone is slapping like mad. The "60W" rating is more to the point: it is comfortable *in hi-fi use* with a 60W amp NOT clipping, implying more like 6 Watts average.
It helps to get in a *small* room. Like a car. Even then, 4-inch car-speakers usually distort when fed the full 16W-20W that most car-audio amps give. I have 5-inch in front, 6x9 in rear, of a small sedan, and the speakers "sound stressed" somewhat before the amp does.
OTOH, you can use a proper size speaker which will move a proper amount of air.
Look at commercial amps. The small Champ is still a 6-inch (and only 5 Watts). 8-inchers are popular for low-price amps in the 10W range.
Eminence 820H or Jensen MOD8-20 or Jensen C8R would be sweet good-size cones. The MOD is also low-price. A 12"x20" sheet of plywood with 1x4 sides is good baffling for Eights in guitar-duty.
Hey, uhm...
What does the U1B do??
And where did 7v came from??
Quote from: Rock_on on June 28, 2013, 08:56:06 AM
Hey, uhm...
What does the U1B do??
And where did 7v came from??
My guess is that the two 1M resistors on U1A form a voltage divider cutting the 14V in half. U1B shares this 7V.
QuoteWhat does the U1B do??
Nothing. Taylor picked picked a dual opamp for the design just because they're more common than single op amps (maybe more easily found/available).
-Walt
Finally finished the TG today. It sounds great! Its mounted in a hastily put together cab of 3/4" plywood (and lots of caulking). I have it hooked up to a celestion G12T and its got this great, light overdrive sound to it when its cranked. My Neutron Filter goes exceptionally well with this amp. Does get some hiss/hum when i fire it up in certain rooms, but not too terrible.
BUT!
Can't get the tone control to work. Has anyone successfully added a BMP tone stack into this build? If so, then how?
Got to play it today for about a half hour. It got HOT. its in a 1590BB (I think) its really roomy, and I thought the case would allow enough mass for good heat absorbtion. I guess not. I'm going to add a .25 X 1.25 X 8" bar of brass tonight, and hopefully will have solid results.
Would using an incandescent lamp instead of an LED help or hinder? I was thinking about trying to throw in some stuff before the giant to draw off some current.
Right now im powering the LED off the PCB's regulated output. Its a 16v 4a power supply feeding the thing, and I think it really needs to be taken down a notch.
I figure this will also clean up the sound a bit. It gets a bit gritty when you dime it. or really get close to dime-ing it.
Anyone use anything other than a 10k for the volume pot?
I might be misunderstanding you but I think you have made some inaccurate assumptions about electricity. The amp will only draw as much current as it needs. Connecting something else on the supply like a bulb will draw more current from the supply but it will not divert any current from the amp.
The TG distorting when you crank it is normal. Some people like the way it sounds, others try to avoid it by turning down.
What effect are you going for by changing the value of the pot?
Yeah, the more I thought it about it, the less sense it made.
I was trying to clean up the sound a bit, as the amp was clipping when the volume was at 1/3rd rotation.
Then I figured out that the issue wasnt so much with the amp circuit as my tone circuit.
I've been trying to get the tone control to work, and with the many and varied permutations i've used I haven't gotten it yet.
The last one, wired up yesterday, is close. Its a modification of the 18w tone control found in this thread.
The sound is now MUCH cleaner. and yes, it clips when cranked, but not nearly as quickly as it was with
the last few bootleg tone circuits i had in it.
The issue now is that the sound is not completely cut out when the volume is at 0. I wired the lug 1 pad to the
tone control instead of the volume, and the output of the tone goes to the volume pot, which has lugs 2 and 3
going to the pads on the board. The tone works well, I used a 1n5 for the high end, and a .47 for the bass
(which needs to be smaller), so no worries there, but wiring it like that isn't quite right for this circuit.
I'm going to try putting the tone control on the output of the volume pot, which will hopefully allow the the signal to be
cut out when the volume is turned to 0. lugs 1 and 3 of the volume will go to the board, the wiper to the tone circuit,
and the tone's output will go to the vol 2 pad on the board. Keep your collective fingers crossed for me.
That's that for that.
The Large brass bar i put on as a heatsink seems to have worked. I only played it for a few minutes (maybe 10 or 15), but the bar was
only slightly warmer than room temp. A HUGE difference. Its about a pound, or pound and a half of brass, so we'll have to
see what happens after 30min to an hour of playing, but I have high hopes.
Taylor, don't you have heat issues with your small enclosure then? I remember seeing yours and it was only a 1590A enclosure.
Also, wouldn't it be easier to instal a small fan such as these to dissipate heat?
http://rato.e-nitiative.eu/product/details/velleman/electronic-components/bsspc1/M640E442?flang=en
http://rato.e-nitiative.eu/product/details/sunon/electronic-components/bsv1225/S8042006
Or would it cause extra noise? I'm thinking of having a go at it with this fan.
the fan would definitely add noise.
mines in a taiwanese 'B' i think. it might be a 'BB' though. In any case, its roomy. it just didnt have enough mass for heatsinking.
It has more to do with the power supply than anything. With a 12v power supply, you should be good. Mines a 16v, so there is
quite a bit of heat. Just use the screws that secure the tabs to mount a decent sized piece of scrap metal. It works.
I've never had any problem with mine and I use it all the time with guitar, bass, and synth. I also seem to rattle it off the cab a lot so it gets beaten up and handles it well. It does get warm but never more than that. However, I always use it in its clean range of volume, never distorting.
Worked out the Tone control problem.
I used the modified marshall 18w posted by PRR a while back, and in order for it to work properly, it needs to come AFTER the volume control, so the wiper of the Volume is the input of the tone circuit, and the output of the tone circuit is wired to the pad on the PCB marked '2'.
I used a small piece of perf board to mount the components, as the only 1K resistor i had was HUGE! it fits nicely into the amp though, and if you ever wanted to tweak the circuit, the small board makes it very easy. I suggest using a B10K pot with center detent for the tone knob, the build just seems cleaner this way.
After a few tweaks, the modified 18w tone works great! It dials in a really clean sound, and allows me to push the volume much further before it distorts.
Thanks PRR!
Much thanks to everyone else who contributed their wisdom/advice for this build as well. Your comments and of course your math were greatly appreciated!
Thanks to Taylor also, as this is a great amp!
Glad you sorted it out. Enjoy!
Thanks Taylor! LOVE IT!
P.S. - finally got a multimeter. You know, in celebration-like.
Just stumbled across this thread, the TG looks like a great build! Does anyone know what its input impedance is?
Quote from: patricks on August 13, 2013, 01:33:11 AM
Just stumbled across this thread, the TG looks like a great build! Does anyone know what its input impedance is?
Probably ~500k
Cool, thanks! I'm planning a microamp build and was wondering whether I could just connect the output straight to the TG but I'll just make sure to build in a "pre out" and a dummy load. :)
Ok guys, Its 99% finished. I installed a speaker out jack, a DC in jack, made plugs for each ( love right angles! ), re-worked and cleaned up the insides (shortened wires, removed remnants of old configs, et cetera), and put it all back together in the "sheissbox". So-named due to the odd shade of brown used for the caulking, as well as the lack of any sort of care given to its construction. Its spot on. Everything works, The heatsink is perfect (I can play LOUD for a long time.), and I paired it with the azabache to see how it would sound.
Amazing.
It really goes great with the aza in front. The next foray into tiny giantdom will be the full custom amp, with switchable "lead" channel and a reverb.
Has anyone tried that spring reverb pedal? It takes 12V to power it so....
Thanks again to everyone!
Hey guys... yeah I'm back.
SO my TG is acting up when the volume is at or above 3/4. The sound cuts out, and or volume goes way down for a second or two, has this kind of overworked-tired-fizzy type of sound, and then it comes back. It happens mostly when I bang out barre chords at this level. I added a Tone control on the output of the volume pot, but other than this, the build is stock.
Any ideas?
should I nix the tone control?
I feel like when I first made the amp it was able to go to max volume without any issues, but can't say that I really remember.
> The sound cuts out
Do that, then put your finger on the chips.
Can you hold it? Or does it burn you?
PRR,
The outside of the enclosure and the brass bar were "decently warm", not "fry an egg". The Chip was probably very hot, but due to the massive brass bar I attached to it, Its a bit of a process to open it up. Could this be caused by over heating? Should I work on finding a more efficient heat sink?
The symptom suggests over-heating. Either the chip or a dubious solder-joint. So I think it has to be opened.
Thanks PRR.
I'll open it up and triage. First I'll check and re-wet the joints, but as far as heat sink, any suggestions for a good one? I tried to look at Mouser, but there soooooo many, I don't even know where to begin. I figured the massive bar of brass would be enough, but obviously not. maybe if I used thermal compound as well? The thing is, The tabs are mounted to the enclosure, and the the bolts go through the brass bar, holding it on the outside. Transfer seems ok, though I haven't broken out the pyrometer yet...
The goal is to be able to crank this amp up for long periods of time. I plan on using it for small coffee-house type gigs and home practice at lower levels, but also to noodle about with the old bandmates (which is where the volume cranking comes into play). With this in mind, would it be better to use the TO-3 metal can version of the LM338 and just wire the leads into the board? It could then be externally mounted and use one of the larger heatsinks?
Got the Thermal compound in place. Amp didn't fart-out as much as before, or nearly as early. Will check solder joints and go from there. It is already better than it was. Temp of the casing and brass was at 77*F - ambient temp is about 75 or so.
Thanks for that follow up, perhaps it will help others.
Hopefully I'll have more concrete data this weekend. Haven't had a chance to really blast it since the last post.
I did go over every joint though, and a few did seem suspect.
When I know more, I'll post some findings.
Vintage Handmade (strat-ish) with 3 Giant Single coils --> Neutron --> Azabache --> Tiny Giant 112.
TG Volume @75%, Tone @80%, Guitar Volume and Tone @10
Played with azabache on most of the time.
After about 30 min, casing and brass were merely warm. The heatsink is not the most efficient, and I have heard from other TG builders that a PC Processor Heatsink works very well (If only they could give me a part number! Argh!), but the brass seems to work. Haven't had to raise the TG volume more than 75% as I'm using the Aza as a boost/overdrive. It may be that putting the vol. at 100% would again make it cut-out. haven't tried, as the settings I used were LOUD. I will continue to search for a real heatsink (you know, with fins and whatnot) but until such time as I find one, this will do quite nicely.
Had some issues with my Neutron (who doesn't?), and the guitar needs some TLC in the electronics dept, but overall, played loud and proud w/o cutting out due to the amp. Success?.... Perhaps....
hi again! 1st sem's midterms is done. We are currently in Finals now. I have time again to do this.
i'm almost done and still my PS is my problem. our shop here does not have LM1084-85 (fixed or ADJ) and LM337-338.
ok, im done in power amp and preamp section. this is the last thing I need to do.
they also said that they have no 1n4004-4007 and they gave 1n540 instead which is according to them a 3A rectifying diode.
what IC is left for me now? I have 24V AC and needs 12-15V regulator.
So the evolution of the Tiny Giant continues! (and here you thought I was done...)
The goal is to build the GM/Cook spring reverb into the same chassis as the TG.
I located a 7 x 4 x 3" hammond enclosure that will fit everything, and will be mounted into the cabinet.
The reason for the 3" depth is due to the fact that I want to put in an actual heatsink to replace my hunk o' brass.
The heatsink I'm looking at is 2 x 1 x 2.5" (roughly), finned, large aluminum, and has a thermal resistance of 3C/W.
I plan on mounting it to the regulator only, using wire leads to attach the reg to the board, and attaching the power amp to the chassis itself.
Anyone have any idea if this heatsink will be enough? 3C/W was the lowest TR i could find, and from what I've been reading,
this should provide good heat transfer. I'm using a 16V 4A powers supply, and was thinking of getting a 15V one to reduce the
amount of heat on the Reg just to make the whole heatsinking thing easier/ more efficient. Am I correct in this assumption?
Should I mount a sink to the power amp as well? It seemed like only the reg was getting hot.
The 11.6V out from the TG board will be the power for the reverb board. Is there a 'neat' way to connect the grounds?
My thought was to use a jumper to make two "lugs" off the power GND input on the TG and attach the GND's that way.
I was thinking of changing my tonestack, and instead using a modified version of a tonestack from an ROG effect I like.
I plan on adding a second stage between the preamp and power amp sections to power it, but I'm still working that one out.
The spring reverb unit is modified to only have 2 controls: Reverb and Level. The Input and Reverb drive pots were replaced with trimpots on a small board.
The reverb will not be bypassable, and I omitted the power switch. This will effectively give me 4 knobs on the TG: Vol, Tone, Rev, Lev. The circuit will run:
Input -> Reverb -> TG preamp -> tone stack -> TG Power amp -> Out
THEN by the gods, it will be finally done, and I can put it in a nice cabinet made from 1/2" dovetailed pine boards, 14 x 14 x 8" and have an amp I can actually carry without breaking my freakin back. Remember the days when you could carry your amp and guitar at the same time to a gig? I do... and they were long ago.
Wow - that sounds great. Nice work!
QuoteAnyone have any idea if this heatsink will be enough? 3C/W was the lowest TR i could find, and from what I've been reading,
this should provide good heat transfer. I'm using a 16V 4A powers supply, and was thinking of getting a 15V one to reduce the
amount of heat on the Reg just to make the whole heatsinking thing easier/ more efficient. Am I correct in this assumption?
That heatsink sounds like more than enough. I was using a very small heatsink that would get warmish, and then switched to a larger (but still fairly small) heatsink that I scavenged from a broken motherboard. This heatsink was cooling the graphics chip on the motherboard, and was a perfect fit to stretch across both chips on the TG. It is blue anodized aluminum with some cool asymetrical fins. Never had a heat problem with it.
Here's a better idea for you... instead of getting a lower voltage power supply, just change the TG (LM338) power supply to a higher voltage. If you change one of the two resistors that set the output voltage of the LM338, you can make it put out 14 volts. The TDA7240 can easily handle 14 volts (and might actually get you more output). The 2-volt difference with your 16-volt power supply means that the LM338 will have to dissipate less heat and is a sufficient drop for the regulator to operate. It's win-win-win all the way around.
@ Walt - Wow, thanks man! Great idea on the resistor change! I'm ordering the heatsinks as soon as I finish typing! The ones I found at Mauser won't fit both, but I plan on connecting the LM338 to the board with wires, and leaving the TDA7240 on the board. This will allow me to have the two giant heatsinks mounted inside the chassis, and each IC will have its own heatsink. Thanks again for the info! I guess this means I'll need to order another kit from Taylor...
@ Taylor - My Norton Security thinks your site has been hacked. What gives? Is it just a fluke?
The site did get hacked but it should be fixed now. AFAICT it's not anything dangerous to your computer, just spam that they insert into my header (oh my).
I built a Tiny Giant amp a year or so ago, and I love it. Use it more than any other amp.
(Runoffgroove Azabache -> MerlinB Solstice Reverb -> MusicPCB Tiny Giant)
I have started planning building another pair of amps with my brother. Tiny Giant the obvious first choice. But it looks like the TDA7240A might be hard to find.
Does anyone have a suggestion:
1. Where to buy the TDA7240A?
2. Similar solid state power amp to build instead?
Thanks
Check out a bunch of datasheets from various 'chip amps' (TDA blah, etc.) and look for their 'application circuit' examples. Here's a place to poke around for different chip amps (http://www.ebay.com/sch/ICs-Processors-/4663/i.html?_from=R40&_nkw=tda).
Ok Kiddies. Its been a bit since I posted anything, and rest assured, its because I was in the a "lab" doing what Arcanists do best: Godless Tinkering.
So- I've been working on this tone control issue I've been having, to whit; I've tried NUMEROUS (I think the count is in the teens or so) passive tone controls, and none of them has reacted well to my ear.
"Big Muff's" (and the myriad variants) need boosters, buffers, and power. I like my muffs trim and shaved thank you very much. ;)
The "18 watt" (posted somewhere by PRR I think) was close, but horse-shoes and hand-grenades come to mind. :o
The "top boost" (Also by PRR, I think) wasn't quite how I wanted to approach things. :icon_confused:
The SWTC (Jack Orman) didn't appear to do anything, but I like its' simplicity. ???
I've been messing with values, and as of today (TG Tone Control #17ish) have stumbled close to the right track. :icon_biggrin:
The TG with a 12" Yngve Malmstein Celestion G12T has great bass response, so I figured, the "tone" would really involve a control for treble boost without attenuating low end. I'm currently playing a heavily (body) modified SSH MIM strat through an Azabache, into a Forrest Cook spring reverb, into the TG.
Using Jack's SWTC #2 as a guideline, and based on the brightness of the maple/alder strat,
I've soldered up a B5k pot with a 1N on lugs 2&3 that occurs AFTER the volume pot of the TG.
The Volume pot's lug #1 and #3 connect to the "1" and "3" pads on Taylor's PCB, and the wiper goes to lug #1 of the tone control.
Tone pot lug #3 (connected to the 1N) goes to the "2" pad on the PCB.
Technically, this is Bass Ackwards to the original schematic, but it is the ONLY way I could get zero interaction between the volume and tone pots.
The effect using a 102 (1N) cap on the tone is fairly subtle, but definitely "boosts" high end.
I'll continue tinkering, but I REALLY wanted to share this breakthrough with you guys.
My plan is to go down to a 151 or .15N cap next and see where that goes.
TTFN - Moxie
Why not use an active filter? You're already using a chip amp and an op amp, so not much mojo left.
QuoteThe effect using a 102 (1N) cap on the tone is fairly subtle, but definitely "boosts" high end.
I'm assuming the quotes mean you understand that's impossible.
Figured it would be easier to use a passive tone control. If I can't get this right, I may have to go the active route.
I've already got the TG's power supplying the GF Cook spring reverb, would adding another "power tap" be an issue?
The PS I'm using is 16V 4A. Not sure if I need something with more juice or not.
"boosts" is a term I used for lack of a better one. I'm still not exactly fluent in the electronics lexicon.
The control brightens the sound without cutting the bass response. That was the point.
Hi everybody,
How much tolerant is the tiny giant with the input voltage WITHOUT the regulator?
I bought a 12v lipo battery to transform my tiny into a "portable tiny" with the idea to plug it after the regulator. But I just received the battery and I see it outputs almost 13.6V when fully charged.... Will this damage the chip?
Thanks for the help!
Mat
That should be fine, but if you're worried always check the datasheet for the chip.
Thanks for the help.
On the other hand... I just was impacient and I did a quick test plugging the battery into the regulator (the same place I plug my 25V laptop PS), thinking that it would not work. I had the idea that the regulator needed at least 15 or more to work properly.
My surprise was that it worked fine... I left it running during 2 hours with my Ipod in, to test the voltage drop of the battery, and I was even more surprised to see that even at voltages of 11.5 from the battery, the amp was still running.
I was assuming that if the regulator does not receice enough voltage it will not provide output, ... but maybe I'm wrong and the only issue if you feed low voltage to the retulator is that it will not "regulate", and simply pass the input voltage... But I have no clue.
Do you know what happens if you feed 12 volts or less to the regulator?
QuoteDo you know what happens if you feed 12 volts or less to the regulator?
If the regulator is set for 11.6V output (as it is in the TG), you need an input voltage of 12.85V to get it (11.6 + 1.25). At any input voltage less than that, you'll get (Vinput - 1.25). So a 12V input would produce 10.75V output.
The TDA7240 is pretty tolerant of different supply voltages (as it was intended for car use). There are graphs in the datasheet showing Output power vs. Supply Voltage. The graphs show the supply voltage down to 9V, and the output is fairly linear for the whole graph.
I think you can take that to mean it would be safe to power the TG (including the regulator) with any voltage greater than 10.25V (although your output would be reduced accordingly).
Aha!
This explains pretty well what I see in mine. My voltage is still higher than 11 so even with the drop out of the regulator the TDA7240 is still able to work.
Thanks for the clarification, this opens up some more options in my plans.
Mat
As a bit of an amateur, im always posting asking for help, so for once I thought I'd post about a finished and successful project.
Just want to say, this amp is great! Finished this a good while ago now and it hasn't failed me yet. I use it as a practice amp (the case is just an old wine crate), its loud and at higher volumes distorts nicely (nothing glitchy or harsh sounding). At first I was getting loads of motor boarding at high volumes but this was solved when I changed the power supply. I didn't have enough power (I thought I could get away with lower than the recommended spec) but now I've switched to 15v 5 amps and haven't looked back.
anyway here it is:
(http://farm4.staticflickr.com/3732/11911191236_58380bc8bf.jpg)
(http://farm4.staticflickr.com/3757/11910307035_cfb4820148.jpg)
I was going to cover it in some cream vinyl and bling it up with some sexy retro chrome, but i've got used to it looking this rustic and kind of like it now.
Great PCB, an easy build, packs a punch and sounds amazing!! Thanks!
Looks great - keep it rustic!
+1!
awesome job i like it
Would love to be able to have a line in to connect an mp3 player or iPod. Anybody have an idea where to tap into the circuit, maybe after the volume pot?
Thank you!
I would try to add a line in after the buffer with resistors for mixing.
Any chance the kits will come back? Tried building my own, but I get a lot of squeals and throbbing.
Squeals and throbbing ::)
Forgot to add some voltages:
LM388T
Adjust (1): 10.83
Vout (2): 12.03
Vin (3): 19.41
TDA7240A
1: 5.55
2: 5.58
3: 5.48
4: 0.00
5: 5.58
6: 11.93
7: 5.59
TL072
1: 5.71
2: 5.51
3: 5.53
4: 0.00
5: 5.75
6: 5.83
7: 5.84
8: 11.65
It seems strange to me that pin 3 of the TDA has 5v on it, as it's the input, but according to voltages posted a while ago in this thread, my voltages look good. I've checked that both the LM338T and the speaker out are electrically isolated from the chassis, which they are; however the speaker isolation is a bit strange.
One speaker connection is isolated around 8k from ground while the other is about 440ohms. That seems strange, but it might be something internal to the TDA causing those readings.
I fixed both TDA and LM338 with brass screws to the chassis, but I've isolated the LM338 using rather heatshrink and rubber washers. Head shrink around where the screw meets the LM338 tab and the rubber washers on either side. Seems to work well.
I can't seem to think of anything else! Thanks
I've audio probed the circuit (using a sick keyboard drum track) set up with the output of the keyboard into the input of the tiny giant. I severed both output wires to the speaker from the circuit and probed around with a 0.1u cap on the tip and the sleeve to ground of a jack.
I good audio (quite, but that's expected from this keyboard going into a passive speaker) all the way through into the TDA chip on pin 3. I then probed the output pins. From each pin I get a very distorted signal. Might this be due to the large output of the keyboard? It is a output/headphone jack, which I suppose is very large.
I reconnected the circuit and it works(ish). Not sure what happened. Now, I get very hot audio coming out, most likely due to the hot audio coming in, but it cuts out every 5-6 seconds to for half a second then comes back to normal audio ???
Tried it with guitar and the same thing happens, but when the volume is turned up anywhere past a whisper, it distorts, tremolos, throbs, sputters, throws a tantrum. Oi.
Some people had similar trouble when using noisy and/or underpowered supplies - what kind are you using?
Kits for this will be back at some point but I'm not sure when.
Not sure when Hubig pies come back either ... :icon_lol: :icon_lol: :icon_lol:
Still thoroughly enjoying my TG , which now lives in the gig bag as a backup/spare amp !!! Works Great for that too !!! :icon_mrgreen: :icon_cool: :icon_cool: :icon_cool:
Quote from: Taylor on March 02, 2014, 11:06:05 PM
Some people had similar trouble when using noisy and/or underpowered supplies - what kind are you using?
Kits for this will be back at some point but I'm not sure when.
I will look forward to their return!
The supply I have is spec'd at 19V (19.41V) and 4.74A. It has three prongs, although based on PRR's way of seeing if the third prong is actually earth grounded (some 1ohm from the third prong to dc out), it seems it is not.
I had throught that was enough amps/properly grounded, but I suppose I will find another one and see what happens! Thanks for the reply.
Is it odd to have voltage on pin 2 of the TDA? There are two voltages posted in this thread, supposedly ok, one having voltage there and the other have none. :icon_confused:
> strange to me that pin 3 of the TDA has 5v on it, as it's the input
The input circuit has to be "somewhere".
The LM386 managed to get its inputs to ground, but that is unusual.
Mostly, all signal pins should be at "half supply".
You've seen 9V pedals with a lot of stuff biased to 4.5V.
Here we have 12V so you expect 6V. Somehow everything is 5.5V. I believe this is normal. We say "half supply" but it really depends on the pull-up pull-down transistors. I can easily believe there is a half-volt difference between them, and that the 5.5V bias point has been carefully designed-in.
> odd to have voltage on pin 2 of the TDA?
If it is below 1V, the chip goes to StandBy and won't play. "Normal" is to let it go loose and it will find its own level, which IS the 5.5V bias point.
QuoteOne speaker connection is isolated around 8k from ground while the other is about 440ohms.
That's about what I have on mine, and it's working fine. I would say this is normal.
Quote from: PRR on March 04, 2014, 07:44:21 PM
> strange to me that pin 3 of the TDA has 5v on it, as it's the input
The input circuit has to be "somewhere".
The LM386 managed to get its inputs to ground, but that is unusual.
Mostly, all signal pins should be at "half supply".
You've seen 9V pedals with a lot of stuff biased to 4.5V.
Here we have 12V so you expect 6V. Somehow everything is 5.5V. I believe this is normal. We say "half supply" but it really depends on the pull-up pull-down transistors. I can easily believe there is a half-volt difference between them, and that the 5.5V bias point has been carefully designed-in.
> odd to have voltage on pin 2 of the TDA?
If it is below 1V, the chip goes to StandBy and won't play. "Normal" is to let it go loose and it will find its own level, which IS the 5.5V bias point.
I knew that, and I knew I knew that, but I don't know what I didn't know it when I was debugging. I guess I have bias blindness :icon_lol: Thanks for the info!
Quote from: waltk on March 04, 2014, 08:26:21 PM
QuoteOne speaker connection is isolated around 8k from ground while the other is about 440ohms.
That's about what I have on mine, and it's working fine. I would say this is normal.
Good to know! Looks like most things are checking out and leading up the power supply. Off to scour amazon. Thank you all very much.
Can't wait for the kit to be in stock :)
according to the guy who runs that store it'll be abt 2 months or so
Gotta get rid of those USC athletes, if you know what I mean. :(
Quote from: mth5044 on January 31, 2014, 04:00:19 PM
I would try to add a line in after the buffer with resistors for mixing.
Does anyone have more info on how to do this or a link? I"d love to know. Working on a project myself right now.
Have a look at the post by PRR on page 6 of this thread.
The TG and kit are back in stock. I've also totally redone the (innards of) the MusicPCB website so hopefully everything will work more smoothly now. Please let me know if you have any trouble with the new site.
I just ordered a cab for this and am putting it together soon. I have an old 20v 3.25A laptop power chord (http://shop.lenovo.com/us/en/itemdetails/40Y7696/460/FB655FA7A2834E04AED9731463CD174E (http://shop.lenovo.com/us/en/itemdetails/40Y7696/460/FB655FA7A2834E04AED9731463CD174E)). Is that okay to use or too much?
Power-wise that should be fine, though I believe some people had noise problems when using a supply with no ground prong on the AC side. Just something to watch for.
Good to know!
Any current deals or "ideal" power cords out there that I should know about since the last postings on the subject?
Quote from: Taylor on July 07, 2014, 12:18:10 AM
The TG and kit are back in stock. I've also totally redone the (innards of) the MusicPCB website so hopefully everything will work more smoothly now. Please let me know if you have any trouble with the new site.
yay! Ordered today.
While my old one lived (i killed it while trying to "fix" things) I found that it wasn't too friendly with pedals i tried. Has this been discussed? Are there any ideas on how to adress this with modifications.. Well, I will start reading the thread. :)
I thought that the word was that it is good with pedals. My board is populated, I'm just pulling together my cab and speaker.
Yeah, I had it mixed up with something else.
In what way was it "unfriendly" with pedals in your estimation?
FYI, if anyone is looking for a cab, this guy makes great champ style cabs at a great price. He does tolex and tweed. With hardware or without. I just ordered a tweed one from him.
http://mergili.com/cabinetsale/
Quote from: Taylor on July 09, 2014, 02:07:56 PM
In what way was it "unfriendly" with pedals in your estimation?
No, I was completely mixing it with something else that uses a chip amp that begins with TDA7* ;D
Seems I don't have any 2.2ohm resistors. How important are those values?
They matter. Together with the two 220nf caps they are for frequency stability of the output. According to the datasheet going any bigger could cause oscillation. "Too low" condition is not explained, at minimum I reckon you'd start to lose audible high frequencies as you go lower. I also think the amp probably doesn't like driving smaller impedances, maybe it'd overheat sooner or make sputtery noises.
If you really don't want to buy anything and you have any small value resistors around you can always parallel and series connect them to get the value you need.
> don't have any 2.2ohm
Five 10-Ohm resistors parallel is close-enough.
OK... so back when the PCB wasn't available, I got together the bits required and did up a stripboard layout. I know the parts were working when I got them because I had it all running fine on a breadboard. Now that everything's soldered to the stripboard it's not working though, so I'm appealing for some debugging help.
Here's the layout I came up with, in case I've made a mistake there:
(http://i.imgur.com/sTBBkPA.png)
On that image, the back pins of the TDA would be the higher 3 of the 4 available slots - I ended up drilling holes between the traces, ensuring pin 4 was completely disconnected, then attaching pins 2 and 6 to the outer traces (I hope that explanation makes sense). Relatedly, I'm relying on the enclosure to join up my grounds - I'm using metal standoffs attaching to the outer strips and not using a pad behind the TDA. I'm fairly confident they're all connected, having done continuity checks with my multimeter. I noticed the official PCB seems to be using the opposite side of the TL072 to me, so that's different as well.
When I power the board, I'm getting a brief pop through my speaker, then silence. I'm using a 1.2k resistor and have ~13.6V out of the regulator. On the pins of the TL072 I have:
1 & 2 = 6.8V
3 = 6.49V
4 = 0V
5 & 8 = 13.6V
6 & 7 = 13.0V
Do these sound plausible, given that I'm using the opposite side of the IC to standard?
TDA pin readings:
1, 2 & 3 = 0.8V
4 = 0
5 & 7 = 0.09V
6 = 13.6V
Any advice on how to narrow down other potential problems is appreciated - I've about reached the limits of my experience/knowledge. Hoping I haven't killed one or more of the ICs with my sub-par soldering skills, but that isn't entirely unlikely.
Quick update, in case anyone is wondering - I made myself an audio probe and I'm definitely getting good audio right to the TDA. I can't identify any connectivity issues for the TDA itself, so I think I've probably killed the chip itself somehow. I've ordered a replacement...
I "scored" a crap one off the bay. Might have been Chinese. Might have been a fake. Anyway, didn't work at all - much like yours, as I recall. Replaced it and it worked just fine after that.
(http://38.media.tumblr.com/8759c75938cc41a01330c266ad980048/tumblr_na7ng6GntG1r1qbzzo1_500.jpg)
added a james/baxandall tone stack, my favorite out the 3 tone controls i tried. (pcb available on my blog)
(http://38.media.tumblr.com/19c5a2aeee2e0868a524322725c12f24/tumblr_na7ng6GntG1r1qbzzo2_500.png)
thank you taylor for getting this back in stock!
Looks great, Petter! I'm curious as to where you placed the tone stack relative to the Tiny Giant circuit.
Thanks John!
(http://31.media.tumblr.com/b6c7b010896eef1adcbb7e81bf8b2438/tumblr_n9wnidGaed1r1qbzzo1_500.png)
"In" on the schematic is connected to the Tiny Giant PCB vol hole 3. "Out" is connected to 2, and GND to 1.
(The values comes from Super-Freq's blog, mostly)
Thanks. I'm kinda new to playing with tone stacks and haven't had success in the past trying to add them to amps. So you sort of wired it in parallel to the volume pot like this?
(http://i1160.photobucket.com/albums/q485/jdansti/88F34274-A23A-4C17-9DE4-815162E3ECDB.jpg)
If so, that explains why my tone stack experiments never worked.
Sort of, yeah, I mean I don't have two volume pots, but I'm sure you understood that.
I tried the treble-mid-bass type stacks used by fender and marshall, didn't like them one bit for some reason.
The Stupidly Wonderful Tonecontrol v.3 or something like that was pretty neat for being a one knob tone Control.
Also goes in right Before the volume knob.
Something I wanted to do, but wasn't successful with pulling off was to use the 2nd IN/OUt channel on the TL072 for optional low-gain overdrive. Would love hints on how to do that, because what I did sounded like ass.
I built a Bandaxall, Fender and some other tone stack a while back and just tried placing it in front of this amp: http://www.amazon.com/gp/aw/d/B00C4OP75S/ref=sr_sp-atf_title_1_1?qid=1407914585&sr=8-1
It didn't work - probably because I just stuck it on the front end instead of after a preamp.
Hm, I got some results enough to feel comfortable that i had put everything together right with both the Orange Micro Crush and the Orange Micro Terror, just between the input jack...
There must be something going on that I haven't learned yet about the proper tone stack location within various types of amps.
New chip is in, everything installed in the enclosure, and it lives! So, that vero layout is verified OK in case the PCBs ever go out of availability again.
Just got to stick some "Tiny Giant" text on the enclosure somewhere and then I'll post some pics of the finished product.
Hello, everybody.
My first attempt at the Tiny Giant has thus proven unsuccessful and i would like to know where to begin troubleshooting.
FYI: I am trying to wire a single coil pickup directly to "in," and an 8 ohm speaker directly to "out."
I have a 15a 5v power supply. upon powering up the circuit, i get no noise but my heat sink heats up quickly.
???
thanks
Well, a 15V 5A power supply would work better than a 5V 15A power supply. Assuming that's a typo, you should check to make sure there's no continuity between the tab of the LM338 and your heatsink/enclosure.
Quote from: waltk on August 21, 2014, 10:19:32 PM
Well, a 15V 5A power supply would work better than a 5V 15A power supply. Assuming that's a typo, you should check to make sure there's no continuity between the tab of the LM338 and your heatsink/enclosure.
i did have the LM338 bolted directly into my heatsink. after i fixed it, i still have the same problem. is it possible that i fried it?
The LM338 is supposed to have it's output protected against short circuits, so maybe it's still OK. Is the heatsink shared between the LM338 and TDA7240? Do you know which one is producing all the heat? Did you go through the build guide and verify that things that aren't supposed to be connected really aren't? It's OK if the TDA chip tab is grounded, but not the LM338. Neither speaker connection should be grounded.
The LM and the TDA do share the same heat sink, but i have the silicon spacers behind both. The LM is the one producing all the heat. Nothing is connected to ground that shouldn't be connected to ground. still no noise at all.
i was checking continuity and accidentally, one of my leads bridged two pads and i got a crackle through the speaker. so far, that's the only sign of life.
Don't the spacers go on each side of the chip ?
rearding the 1uf cap on pin3 of the 7240, can a polarized electrollytic one be used? if so, which way should the positive/negative side go?
i was thinking, instead of adding a tonestack at the end, would it be possible to essentially put an amp sim pedal in front of the Tiny Giant. i was thinking that this would make the Tiny Giant sound like whatever the amp sim pedal is emulating, and give you an eq. so, if a citrus graphic MKII was put in front it would sound more like an orange, and DLS would make it sound like a marshall, etc. or am i wrong? cause i was thinking about doing that if possible and making a small amp to test effects instead of using my mesa at all hours of the day.
Quote from: rocket8810 on August 28, 2014, 10:59:10 PM
i was thinking, instead of adding a tonestack at the end, would it be possible to essentially put an amp sim pedal in front of the Tiny Giant. i was thinking that this would make the Tiny Giant sound like whatever the amp sim pedal is emulating, and give you an eq. so, if a citrus graphic MKII was put in front it would sound more like an orange, and DLS would make it sound like a marshall, etc. or am i wrong? cause i was thinking about doing that if possible and making a small amp to test effects instead of using my mesa at all hours of the day.
For what it's worth, I've run the fetzer valve in front of the tiny giant with satisfying results, and also the valvecaster.
would it be safe to run the TG with a speaker rated at 200w? what would be the harmful effects to the speaker?
That would be fine. The power dissipation rating means it can handle less than or equal to that amount of power before damaging the speaker, so it's fine to send less than the maximum for which it's rated. In fact, you should always use a speaker rated for more than your amp power if you don't want speaker distortion.
People sometimes write that "underpowering" a speaker can be bad but I think this is at best a fringe scenario and not something you should worry about here.
Speaker ratings can be listed in various misleading ways, so always go by RMS, not peak ratings.
> be safe to run the TG with a speaker rated at 200w?
Absolutely safe. Go ahead.
The flip-side is: a speaker built to withstand 200 Watt abuse has to be heavy-duty. Which means heavy. Which means less sound-output per Watt.
You *may* find that a light-cone speaker rated say 30W will (for the same power) be louder in the room than a similar heavy-coil speaker rated 200W.
And there are special-purpose "high power" speakers that just suck for guitar. A 200 Watt car sub-woofer will be very lame in the 80Hz-5KHz guitar band. But it stays the same lame all the way down to 50hz or 40Hz. Which is the only way to get gut-slam in a small size. But the 40Hz-80Hz does no good for guitar (even drop-tune), and the excess mass to pull it down an octave clobbers 6 octaves of guitar sound.
_____________________________________
> Speaker ratings can be listed in various misleading ways
Yes. If possible, use speakers RATED for guitar.
Guitarists max-out their amplifiers for long periods of time; guitar-speaker makers have to rate them that way.
Car-speakers are usually semi-honest. Some owners do max-out the amps (you have heard them drive by). Especially the ones who put in aftermarket speakers. The Tiny Giant is fairly safe for most larger car speakers, because it "IS" a car-radio amplifier with a little less power than a screaming car's alternator.
Hi-Fi owners do NOT max-out their amps. A 200 W hi-fi may have short peaks over 100W but plays at an average power (over a few seconds) of 20W, 10W, or less.
Quote from: jogina111 on August 27, 2014, 10:49:27 PM
rearding the 1uf cap on pin3 of the 7240, can a polarized electrollytic one be used? if so, which way should the positive/negative side go?
If you were to use a polarized electrolytic capacitor the negative side would be closest to pin 3 on the TDA7240 chip. On the musicpcb pcb the negative side would be closest to the 1M resistors.
I don't see that there would be an overly audible problem although it is widely thought that electrolytics should be kept out of the signal path as their noise rating is higher than say polypropylene.
I think it will be alright if it would sound lame since it will only be for practice. I juat became worried when I read somewhere that the amp would overheat when the speaker demands more output current etc..
Taylor, if you ever do a v.2 of the board, it might be nice to include holes for the extra bits to give the 072 some gain, for anyone who does want to insert a tone stack and compensate for the signal loss.
Quote from: Ben N on October 21, 2014, 08:48:24 AM
Taylor, if you ever do a v.2 of the board, it might be nice to include holes for the extra bits to give the 072 some gain, for anyone who does want to insert a tone stack and compensate for the signal loss.
Hmm, what did you have in mind specifically? You can increase the gain of the opamp stage by changing the 220k feedback resistor to a larger value or pot, and/or lowering the value of the 100k from inverting input to ground. But I think you know that so I must be misunderstanding what you mean.
My bad, Taylor--I didn't look at the schematic before commenting, and assumed that the feedback loop was hard-jumpered on the pcb for unity gain. :icon_redface:
On another matter, I spotted a cheap easy speaker cab that might be perfect for some TG projects: http://www.diystompboxes.com/smfforum/index.php?topic=108964.0 (http://www.diystompboxes.com/smfforum/index.php?topic=108964.0)
> assumed that the feedback loop was hard-jumpered on the pcb for unity gain.
If he did that, sensitivity might be low and/or idle hiss might be high.
I do not have the plan at hand, but *usually* a guitar amp must run preamp - volume pot - power amp.
It is difficult to get enough gain in a power amp to bring-up a small signal like guitar.
A power amp usually has higher input hiss than a for-purpose preamp.
It usually works out best to take a moderate gain before the volume control, the rest after. Good target values are 20mV sensitivity at guitar jack and 50mV-100mV sensitivity at power amp. Preamp input should also take 300mV~500mV without distortion (at lower volume-pot setting).
> insert a tone stack and compensate for the signal loss
Ah, a new can of worms. If you compensate all tone-stack loss in the front, then the preamp will have high gain and high output level. Assume Fendery stack with 10:1 loss. Present preamp gain is 3.2, so we hack preamp for gain of 32. If we put in a 500mV signal the preamp outputs 16V, which won't happen cleanly under a 12V supply.
Without a much higher supply voltage (say 30V), the "optimum" is probably preamp - volume - booster - tone - poweramp. Two small stages.
Isn't that a dual opamp? Then he "could" pad-out the idle side and let users do what they will. Stock would be jumper Out to In- and In+ to Vref. Mods could be most anything, which is why _I_ would not encourage it or support it (too many ways for buyers to screw-up and complain).
I would assume (here I go again) that most builders are using supplies of 15-19vdc, but, yeah, I hear the point, Paul. I personally wouldn't mind having the flexibility to use the second opamp, but I get why Taylor would want to keep the platform simple and clear--as it is, there are nearly 900 posts on building it.
> using supplies of 15-19vdc
The Tiny Giant has an on-board 12V (11.9V?) regulator. The power-amp chip is designed for "12V" car audio.
Yes, it could stand more; or the preamp supply could be higher than the power amp supply. But going from 12V to 15V is not a big increase of signal handling. And we do need some filtering or protection for the preamp, so 15V input might be 14V at the preamp.
Yeah, we could double a cleaned input to 28V, or buzz it thru a transformer for 300V. Many things are possible. But as-designed the Tiny Giant does a very useful thing-- guitar to LOUDspeaker, DIY, without the huge box needed to stand out on a showroom floor.
hi all!
I built the tiny giant and it works fantastic!
The only problem is that I was using a friend's 19V adapter. My own laptop adapter is 21.1V...do you think that it will blow my tiny giant up??or is it just the heat issue?
> do you think that it will blow my tiny giant up??
Sorry, no, it won't blow up. (If I thought it would, I'd ask you to get video!)
Slight extra heat should be no big deal, unless it is blistering hot now.
true! it works just fine with 21.1V ::)
thank you very much!
??? :( :(
Sadly, after being lucky for long time, something went really wrong while I was experimenting with the power adapter.
Now, when the Volume goes higher than 60% the amp produces a loud distorted synth-fuzz-like fart. If the volume is lower it plays mostly normally. It is also a bit random, at times when I switch it on it gives this terrible sound at volumes less than 50%
Which parts do you suggest I should replace first???!
072 oe the tda7240
I wanted to take a look at Taylor's site, but my Trend Micro security program has it flagged as a possible malicious site. I can't imagine that's true. Anyone else seen that happen?
Geoff
It happens on my pc.
Quote from: Shoeman on November 03, 2014, 11:27:13 AM
Anyone else seen that happen?
Nope! :) And I'm on the inside of a vast corporate network with doubtless all manner of firewall and anti-virus things going on. If something needs to be blocked, then it's blocked!
I haven't been able to get into Taylor's site, either at home (Avast) or at work (government network), in a dog's age due to malware alerts. I know he has struggled with this, and assures that there is no real threat.
I have avast as well and that blocks me out every time.
So is the site considered safe by those of you who use it? Taylor?
To my knowledge, the reason this happens is that at some point in past years, the site got hacked a few times to insert a bunch of links to prescription drugs, I think as part of some SEO scam (if lots of pages link to your site, Google indexes it higher in searches; scammers place links to their stuff all over the web to inflate their apparent significance). The links weren't clickable, possibly not even visible but in the page source code. I deleted all of that stuff and upgraded to newer software, etc. When I go to the site, I don't get any malware warnings and as far as I can tell there hasn't been any weird stuff inserted into the pages in a long time. To my knowledge there was never anything on the site that actually attempted to get onto your computer or mess your browser up.
Web development is not really my forte, despite having been pretty slick with HTML back in the last millennium. It's gotten a lot more complicated and my available time to become expert on things has drastically declined. So based only on my limited knowledge, I can speculate that maybe the site got flagged by anti-malware software back when it was hacked, and perhaps there is no automatic mechanism to get unflagged over time.
Since I haven't personally seen the warning in a long time, and I still receive orders and emails through the site's submission form, I don't have any way of figuring out how extensive the problem is, nor do I really know how to fix it. I will be thinking about how to figure it out - in the meantime if you can't get to the site and would like to order something, you can email me directly at taylorlivingston at yahoo.com.
Excellent explanation. And I know what you're saying about HTML vs. whatever it is nowadays. My age has a 5 as the first digit ;D I can bypass my antivirus's warning and go to the site, so I will.
Thanks!
Geoff
getting back to the damaged tiny giant:
I replaced everything (tda, 072, lm338) + I didn't solder the tda7240 on the pcb directly but i used 7 wires of 5-6 cm as an extension (i was afraid that the pcb would be cooked)
Now...
It plays normally but in the background it whistles like a 50's AM radio!!
Actually, when I move my hands around it, without touching it, the whistle changes, something like theremin!
1. Is it the extension cables I used for tda7240?
2. Is there some capacitor that has to be replaced too?
I am writing all these just in case someone had had the same symptoms :)
Is it in a grounded enclosure or otherwise shielded? If not it definitely could pick up and amplify radio frequencies.
yes, the enclosure is grounded.
I had faced that case in the past, when the amp was out of the box: I could hear clearly a radio station playing latin music all the time!
But now the case is different, I don't hear any radio station/music, the amp gives that theremin/am radio whistiling only
The power amp chip probably does not like those long wires.
just ordered new pcb and amp chip... I was that close to finish up a 4-year-project, my personal 3 channel battery powered busk amp!! I have to wait a bit more time probably :o
hi all,
i have another question to post, about the tiny giant power supply. I don't know if this is the proper forum, but I think it is close to the tiny giant amp topic.
I have built this power supply:
(http://i46.photobucket.com/albums/f112/fatecasino/18v-dc-power-supply-by-7818_zps1671c8d7.png)
There is something magic happening here, when I follow the following scenarios:
SCENARIO A
1.Turn on SWITCH A(220V) Vmeter = 18V
2.Turn on SWITCH B(18V) Vmeter = 18V
3.Turn off SWITCH B(18V) Vmeter = 18V
4.Turn on SWITCH B(18V) Vmeter = 4V :o :o :o :o :o and the amp of course doesn't power up!
SCENARIO B
But if
1.Turn on SWITCH A(220V) Vmeter = 18V
2.Turn on SWITCH B(18V) Vmeter = 18V
3.Turn off SWITCH A(220V) Vmeter = 0V, the amp makes a blip sound and its power led turns on (just for a moment) after 2-3 secs
4.Turn on SWITCH A(220V) Vmeter = 18V and everything works normally
SCENARIO C
Then, I have a 18V battery pack, I connect it in parallel to the exit of the power adapter, just before SWITCH B
1.Turn on SWITCH A(220V) Vmeter = 18V
2.Turn on SWITCH B(18V) Vmeter = 18V
3.Turn off SWITCH B(18V) Vmeter = 18V
4.Turn on SWITCH B(18V) Vmeter = 18V and the amp of course powers up!
Obviously there must be some C1 capacitor disharge directly into my tiny amp (or into the battery pack in scenario C), and this probably damaged my tda7240a (could be)
I am missing out some theory around power adapters, but what could I change in my power supply circuit in order to make my first scenario work.
Thanks to everyone, I hope this post gives some knowledge contribution :icon_biggrin:
hey all,
i have built this little beauty for the second time now and still no success.
the thing works fine in very very low volume. but when i try to turn the volume up a bit or sturm a few strings together i get this repeating pop sound.
i build this with a vero layout and i have used monolithic capacitor for the 1u values.
i have switched the amp chip, the power supply and received the same results.
any ideas what could have gone wrong ?
(https://www.dropbox.com/s/dt653pk8570y2ov/20141124_094205.jpg?dl=0)
Taylor, this is one serious diy amp! Love this thing. Thank you for taking the time in your wonderful hobby to share and make this great little amp available to the rest of us, and at such an affordable working man's price. I wanted to buy a few more of these because now I'm really hooked, but your website seems to be down. Is there an alternative way that I can get in touch with you to order a couple more complete kits? I plan to add a few pics here in the coming days of my build. The chassis is an old metal Johnson and Johnson first aid case. I built it into its own head cabinet and am working on two 8 ohm 112 cabinet wired in parallel for 4 ohms to get every ounce of sonic goodness out of your sweet creation. I have noted that others here seem to not get much more in volume past about 9 oclock. I don't know why, but mine is clean and mean with discernable volume gain all the way through to almost 2 oclock. Very quiet (minimum him or noise). I'm just loving this sweet amp Taylor. Thanks a million and please let me know how I can buy a few more of these since your website seems to be down. Also wanted to let you know that I am making a name plate for the head and speaker cabs that have my last name, but under that I'm giving you props and adding "Taylor's Tiny Giant". Your work deserves at least that, for sure.
Thought I'd add a few pics of my build. The head cab needs to have all edges routed and sanded, screw hoes filled and sanded and stain/ sealant applied. Then I will finish the homemade speaker cabs to match. If I can get a few more of these kits ordered I plan to do it all up with tolex for the whole shebang. ...hmm can't seem to add images using my smart phone. Images will be added as soon as I can figure this out. Sorry lads.
Cool, thanks for the props and the first aid kit enclosure sounds really cool. Glad you're enjoying the amp! A simple website for uploading images is imgur.com.
Right now the MusicPCB site is down while I switch to new domain name servers and a new platform. The site will be all new so anybody who previously had issues getting onto the site should have no more issues. It may take another day or two before everything's setup.
Thanks Taylor, you deserve all the props anyone here can give for sharing this with us. This is the first amplifier I have built. Granted, it's not "from scratch" but it's as close as a newb like me can get on a first build without feeling way out of their depth. Anyway, thank for the info on your website. Can't wait! I'm still having trouble posting pics. When I kit the "post picture" icon, it only adds the img/img text in my text box, can't seem to get it to do anything else. By the way Taylor, any plans for another tiny giant style amp with a bit more power? I was wondering if two of these in a kind of AC/DC or push pull (wrong term) could be chained together to create an amp with around 35-40 watts at 4 ohms? Anyway, I was planning on originally building this with some kind of preamp in front, but after building it stock, I really love the tonal qualities of this amp clean, as well as the fact that with my boss GE7 eq and Ibanez tube screamer in front for just a little bit of warm breakup, it is sweet, sweet, sweet!
This forum doesn't allow you to upload attachments directly, so you need to upload it to another website like imgur.com, then once it's uploaded, there will be some code on the Imgur site that you can copy and paste into this forum using the [img] tags.
The amp chip used in the TG is a "bridge-tied load (http://en.wikipedia.org/wiki/Bridge-tied_load)" configuration, which means it's actually two channels bridged already. For this reason you can't bridge two TGs to get more power, and because loudness is on an exponential curve, doubling the power actually only gives 3dB more volume, which is a barely noticeable difference. You need 10 times as much power to double loudness, and at that power the build is necessarily much more expensive, difficult, big, dangerous. So the TG exists kind of in a sweet spot. If I needed 200+ watts I would definitely purchase a commercial amp rather than try to build it - companies like QSC are really good at what they do and I couldn't build a better amp for the same price.
Thanks Taylor, that's good to know. If need, I can just mic this sweet little baby up. When I get off work, I'll try to get images up. One other thing I wanted to try to do on top of the power on/ off switch I added, was to add a led on/ off light. I tried with a 12v led light from radio shack. The light came on nice and bright as I had hoped, but for some reason I could not get any sound signal through. I wired it up with the power switch to go directly between the power in and the board. When I disconnected the led light and tied the power on/ off spst switch back direct, it works just fine. What gives? I'm wondering if the 12v led light is chocking the rest of the amp. Should I use a larger v led light?
(http://i.imgur.com/XUKxmQS.jpg)
(http://i.imgur.com/kOzzwPM.jpg)
pics of my head cab, not completed, just fit together for testing out! I will be completing it with stain/ finish and building 2 112 cabinets to be wired in par. Hopefully I can find some good realistic basketweave or similar for the grill clothe
Cool, it looks good!
hi all,
I just received the replacement parts (pcb, tda chip, etc) and:
1)getting back to the power adapter problem, I fixed it with a help of a friend,
it was the LM7818, which on switching back on the amp, it couldn't actually stabilize the voltage and it was giving 4volts instead of 18V.
I added 470 uF in parallel at the output and it works fine now!
2) adding extension wires to the TDA chip does not generate any annoying noise
3) All works fine now, EXCEPT (as usual), after the increasing the volume to 70% I get some ugly bass fuzz/synth noise. I changed a couple of caps, but with no results. Any ideas on that?
Many builds of this work fine without the 470uFd.
I wonder if your 16V power supply is weak?
If it is barely weak, for a bridge-mode power amp like this I would be thinking a BIG cap, 2,000uFd to 5,000uFd. But that is a band-aid for power supply wobble.
ok, I think everybody here has paid intention to what is called...Murphy's law :icon_exclaim:
Which part burns first if the two wires of the speaker output created a short circuit?
I suppose the tda...do you know any reliable store in the internet to get some of them?
According to the datasheet of the TDA2740, it's protected against output shorts across the speaker or if one or both speaker connections shorts to ground. In these cases it will shut down until the short is fixed but should not be permanently damaged.
What Taylor said. This is a CAR audio chip. Car speaker wires sneak under carpet, through door hinges, and over sharp edges inside the body. And in my Honda, if I put a metal case in the trunk, it hits the naked speaker terminals.
Shorts happen. A lot. Far too often to be replacing a chip inside the radio every time.
Car-sound chips "must" self-protect against shorts; either to-ground or to the other live wire. It isn't a very complicated problem. It's more parts, but once the chip-designer is done, they can make millions of chips that don't fail in every-day car wiring mistakes and accidents.
If you shorted and it is NOT working, you have an odd problem. Look for solder joint that did not hold-up under the momentary strain. Then use general debugging process; link in one of the top topics of this forum.
thank you!! I'll check it out. I had just put together the newly arrived pcb+parts..it was working like a charm. I think, it's the 3rd or the 4th time I am attempting to fix this amp. They always work perfectly at the beginning, but then always something goes wrong until I put it in the enclosure. The tda has very sensitive legs, you can easily loose 1-2 legs by just moving it. Well, it's a matter of honour, I have decided to finish this project, no matter how much it will cost.
well, the things go like this
1.after power up, the amp sounds like a distorted 2-stroke-scooter which accelerates and de-accelerates randomly
2.The volume pot does not influence this sound at all, it is steadily loud
3.the tda7240 gets too hot in very short time 4-5 secs
4.The voltages are:
input 18.5v
tl082 pin8 16v
tda7240a pin6 16v
lm338 Vin 18.3V
lm338 Vout 16.1V
Any suggestions?
@taylor: have you thought of selling extra tda7240a pieces in this combo?(http://www.musicpcb.com/pcbs/tiny-giant-amp-pcbcomponents-kit)
Heya,
What voltage and amperage is your power supply?
Is the TDA chip heatsinked in anyway?
You could use a multimeter to check whether the pot is faulty.
The fluttering is consistent with the amp not getting enough current I believe. I could definitely be wrong, but I've made one before and it works great and I've never had any motorboating issues.
Hi!
the power supply is 19.5V/4A, I tried with another power supply, same results thought.
The tda is heatsinked with a really big heatsink. Otherwise it would explode with all this heat that it produces now.
The pot is OK.
It's not exactly a motorboat sound, like some faulty pt2399s, it's much more distorted and loud.
Is there a reliable seller for trying with a new tda?
The parts kits are put together by forum member Waltk, but I'm not sure where he is currently purchasing the TDA chips. I have exactly one per kit so I can't sell extras myself, but he may either have extras or could post the most recent retailer for them. Maybe posting some pictures of your build could help, since you mentioned it was working fine until you boxed it up.
I got my first TDA7240 from xiaobao_semi on eBay. Turned out to be garbage. Thankfully, they appear not to be selling anything these days. My working replacement came from swle2000 on eBay. They're in the UK and they still have parts available, going for £4.51.
thanks bluebunny! just ordered 2 from swle2000. let's see :)
Preparing to build two 12 inch cabs using Jensen mod speakers, 8 ohm each. They will be in two separate cabs. My plan was originally to have one of the cabs with two jacks so that I could run a cable from the amp to the first cab, another from the first cab to the second having everything wired in parallel for 4 ohms. Now I'm wondering if maybe I should put two output jacks in the back of the amp coming from the pcb. If I did that how would I wire them to the pcb/ each other for parallel so that the 2 speakers (8 ohms) can become 4? Thank you.
You would connect one of the SPK pads to the tips of both output jacks, and the other SPK pad to the sleeves of both jacks. Physically, it would generally be better to join the wires at your jacks' lugs rather than soldering multiple wires to a single PCB pad.
Thank you Taylor for your reply, that makes sense. I momentarily forgot just how small the pcb pads are lol
Another quick question. I was thinking of doing something similar to what tech 21 did with the power engine 60. Use the runoffgroove professor tweed as a preamp (similar to sans amp character pedal) with two outputs rather than one and run that preamp to two tiny giant (each in a 212 cabinet). I don't think it will actual be louder per say, but perhaps using that will push more air and the ear will perceive it to be louder...I guess it would essentially be modular amp setup, a couple of power amps feed tone from a preamp. I guess it would be similar to using an aby pedal. Any thoughts on how this may be perceived louder by the ear?
Yeah, that seems a good way to do it. If I'm remembering correctly, you'd get approximately 3dB more from doubling power, and 3dB for doubling speaker area.
Thanks Taylor. I guess now I need to try to figure out how to wire in an additional output Jack to whatever preamp pedal I chose. The only way I can think to do it without significant signal loss between guitar-preamp-tiny giant amps is to maybe wire the two output jacks of the prof tweed in parallel? Or does it really matter all that much going with this type of signal chain? Anyone have thoughts?
> 3dB for doubling speaker area
It's never that simple; but it is a good general rule that more paddle makes more push.
I like to work in quads. Four speakers gets 6dB more bass efficiency due to better air-load, and 6dB more mid-bass level on-axis due to narrower pattern. That's why a Champ or a Giant will BLOW-AWAY many "mighty" amps if fed into a Full Stack (eight 10s).
The two-12" array on the ground (many Fender Twins) is also significantly louder per electrical Watt than any single 10" box. By the logic above, 3dB better bass efficiency and 3dB extra on-axis (better projection to the far corner).
That's assuming "guitar" speakers, and not the highest-power g-speakers. Light cone is also part of the formula. Hi-power speakers have heavy coils and cones to hang-together at 200 Watts. Sub-woofers have heavy cones to leverage against air stiffness in the lowest octave of bass.
Thanks Paul. I sort of figured that, but not in exactly such an eloquent and technical way. I already have the two 8 ohm 12 inch speakers, so that's what I will use for the first build. But I have received my second kit from Taylor and am thinking of using four 10 inch 16 ohm speakers wired in parallel to get down to 4 ohms. Sure I could use four 12 inch speakers, but I love the bassman speaker setup and I'm wondering if four 12 inch speakers would be overkill. Also, I like the idea of a slightly smaller cabinet. I would like to play the two amps together to get a fuller sound, hence the "modular" idea of using the amps similar to the tech 21 power engine 60, and using a rog preamp pedal in the same fashion as a sansamp character pedal to run into both the amps. I'm beginning to wonder if it would just be better to go ahead and use the active aby pedal route. I think it would be more versatile because I could load a preamp pedal after the aby pedal into each amp to give them slightly different tones from each other. Also, as this tiny giant is my first actual build of any electronic (and I'm hooked now) It will give me a reason to build yet another kit.
Taylor, one of the things I really have come to love about your amp design is how uncolored the tone is. It's great for running my various pedals through it and getting great tone. I have one of the first production runs of the Peavey Classic 50. Love the amp and the tone, but it's WAY too much power for what I'll probably ever need, and I can't get it up to saturation volume without tearing up the neighborhood. I also have the Orange Micro Terror, which I really also like, but it does have it's own tube preamp which significantly colors any preamp pedal tone, So it's kind of a one trick pony in my mind. I just have to say, I play the Tiny Giant almost exclusively now for that reason (and also because I put it together myself). Have you toyed with the idea of designing and supplying something similar but a bit bigger like say 40 or 50 watts capable? If so, I would be the first in line to order a few of them. Thanks again.
I am curious that if I wanted an amp with a bit more wattage if I could swap out the LM 338 for an LM3886. I would have to look at the data sheet for that to see what kind of power supply I would need...I'm sure I'd also need a significant heat sink as well, but would the rest of the supplied components and the pcb work fine with an LM3886, an appropriate power supply and heat sink as is? Or would resister/ capacitor values need to be adjusted as well?
The LM338 is a voltage regulator, whereas the LM3886 is an amplifier chip. The amplifier chip in the Tiny Giant is the TDA7240A. These amp chips are different electronically and are physically in different packages with different pins, so they are not compatible and can't be substituted for each other within a pre-existing circuit.
You definitely can make an amp with the LM3886, and there are schematics and kits for them out there, but it would be a different circuit entirely. I bought one of those kits a few years ago but ended up not building it and came up with the TG instead, based on datasheet designs and posts by WaltK. You need to build your own more serious power supply and will have to do mains voltage wiring, which can be deadly dangerous if you don't do your homework on safety.
This is why the TG came about: it's pretty easy to build and pretty loud and pretty clean. Since 40 watts is just barely louder to the human ear than 20, and considering the expense, difficulty, and danger in building a significantly more powerful amp, making the TG seemed a better option to me at that time than building the 3886 amp kit I bought. But that's just me and other people do build very nice high power amps. Check out the DIY Audio forums for gobs of info.
Actually, if you really want more volume you should also turn your attention to speaker designs such as those of Bill Fitzmaurice. You can get a good 5 more dB in the relevant frequency ranges (better than doubling watts) by just building your cabinet in a different design.
Thanks Taylor. The high voltages is what put me off of tube amp kits. I will certainly take a look at the cabinet designs you suggested. I'm still thinking of aby pedal or some sort of modular setup. I understand that I can find speakers with different db ratings per watt and that makes a big difference. Thanks again Taylor.
Can someone please post the pin voltages from a working TG? I have a version with a tube pre I am working on that has signal getting to (and even through) the TDA but there is no amplification (I can hear the signal when I probe pins 5&7, but nothing on the speaker). The vero prototype worked and sounded real nice, but moving the design to PCB has me stuck. I want to rule out circuit design problems as I have already desoldered 2 suspected TDAs and my traces are starting to melt.
If someone wants to look over my design it is here: https://drive.google.com/file/d/0B_Sh_vDhJkMqWVJ4cU45WGZCY1U/view?usp=sharing (https://drive.google.com/file/d/0B_Sh_vDhJkMqWVJ4cU45WGZCY1U/view?usp=sharing)
I know the protection diode is in a weird place (it's where it ended up on the vero prototyping madness). I'd also be interested in knowing people's thoughts about removing all of those filtering bits taken from the Tube Cricket (Diode through 220uF cap) as I assume those would be unnecessary with a switch-mode PS and the LM338. Although I've been wondering if they don't provide some protection (load) to isolate the Vout on the 338 from the ground potential on the cold heater elements on the 12au7.
My PCB has the diode before the 338 and all the filter bits in place FWIW.
Any help would be appreciated but pin volts are really needed, thanks!
There should be 11.5V from the '338. All the power-amp and opamp pins should be 11V, zero V, or half of 11V (5V or 6V).
Which ones are not right?
Adding a hot bottle is outside the original design, and should probably be diagnosed separately. i.e., feed signal to *just* the TG and see what comes out. If that works, problem is around the tube.
Thanks Paul,
From a year or more of lurking, I knew if I was lucky enough to get an answer from you it would help get me out of the head scratching fit I've been in for a week now and into a fresh perspective to fix and finish this thing.
I hadn't thought about bypassing the tube as it seems to be working well as I scoped and probed a signal all the way through it and it amplified and looked and sounded great. But pulling the tube and going direct into the PA will be the next step as it could rule in or out a bad TDA and might identify some bad interplay issues with the tube. As it stands now my volts look fine based on your off the cuff numbers. I have the 338 biased closer to 12.5 volts and I'm seeing 12 volts, 0 volts and around 6 volts on the various pins.
I'll bypass the tube and see where I stand. I've been resisting the idea that the TDA is bad because I've already changed it out twice. But like my mechanic brother says, "When a customer tells me it can't be the alternator because they've already replaced it; it's usually the alternator..."
I wonder if I have a bad cap on one of the PA legs, that could throw the IC into shutdown, right?
BTW Paul, I'd love your take on the schem I linked to and my dumb questions about the filtering bits from the Tube Cricket if you get a chance. How does a fella send you a beer anyway? You do a lot for this community...
I am building a second tiny giant amp, I am currently using a 16 volt 4 amp power supply, can I power both tiny giants with this 1 power supply?
thanks in advance for assistance
> a 16 volt 4 amp power supply, can I power both
If both speakers are 8 Ohm, it should be fine.
If both speakers are 4 Ohm, it is right at the edge of punking-out.
thanks for input, actually 1 cab is 8 ohm and the second cab is 4ohm,,what do you thing of using single power supply in that case?u
Fine.
I have not seen this answered on the thread, can the tiny giant handle a 2 ohm cabinet?
Thanks
The datasheet for the amp chip (http://www.st.com/web/en/resource/technical/document/datasheet/CD00010656.pdf) doesn't list a minimum output load resistance but all of the ratings and charts are for 8 and 4 ohm loads, so I think they don't intend for 2 ohm loads. I'm guessing the chip will just mute itself and shut down with 2 ohms as it sees it as a short but I'm far from sure about this. Could kill the chip for all I know. If it works the amp is going to be more likely to overheat so you'll want a much bigger heat sink.
Peak output current (repetitive) is 3.5 Amps.
Skipping math, this does not support 2 Ohm loads at any reasonable supply voltage.
IMHO: in 2 Ohms it will play softly for a short while, but any serious use will be grossly distorted at a level less than you'd get in 4 Ohms, and then it will over-heat and shut-down. Some rough calculations say it would need an infinite heatsink to stay barely-safe at high output in 2 Ohms. A heatsink from a 100W amp might not be infinite-enough.
Would anyone who has ordered the kit from MusicPCB tell me how long it takes to receive it?
Depends where you are. It took a couple of weeks from memory, but I am in New Zealand, so you'll likely get much shorter shipping times if you live in/closer to the US.
I am in the process of building second tiny giant for stereo and to support keyboard on some tunes. This is a great little amp and is perfect for me to play my line6 x3live thru. I use it to gig and mic the amp, much better than x3 live direct to board. My question is the amp does get warm when play at gog level(I have mine in 125b size box). Is a heat sink needed or is the alim box enuf to dissipate heat, when played for extended periods, say gig set of 1 hour at a time, or is it likely to shut down?
thanks in advance and what a great project
> Is a heat sink needed
Yes!!
It is a car-radio chip. Typically it uses most of the back-side and other surfaces of the car-radio as a heatsink. Bolted to a 125B box may be a minimum-size (unless you have radio factory testing chambers).
It can run HOT. Too hot to hold. It probably should not boil spit. Somewhere in that area it will turn itself off, cool, and go again. No harm is done to the chip (unless it happens thousands of times); however the show won't be the same without you.
thanks for the input
I have found heatsinks at this site http://www.heatsinkusa.com/
can be cut to size will but 1 on top of my 125b alum enclosure, I would think this should keep it cool
Hey all,
Built my Tiny Giant a year or so ago in a recycled Yamaha combo enclosure and I love it! However, there is a spare hole in the chassis and I would love to add a headphone out jack. I wasn't able to find any info regarding a headphone out on this thread, so I was wondering: Is it just as simple as adding a switched, padded output, or will the chip have an issue with headphone impedance??
The headphone problem is that headphones are grounded-jack, the TG output is _NOT_ grounded.
Other problems being far too big a signal, forcing us to waste-away some.
All problems can be attacked. However at the moment I need to attack my bed.
I did figure that the amount of output the tiny giant can provide might be too much for phones, and yeah, that's a lot of wasted energy if it's padded down.
What about tacking a simple 386 headphone amp onto the circuit? Would it be an issue to share the 12v power coming off the regulator to power the 386? Would it be ok to drive the 386 right off the output of the TL072 with a separate cap and volume control?
If you did not already have a Tiny Giant, yes the LM386 is a good way to go.
Tapping from the Tiny Giant is practical, but we have to take care.
There is 6 Volts of DC at either TG output pin. This will cook most headphones. We need a Blocking Cap. (The '7240 chip will shut-down if it sees a heavy to-ground load; I'm not sure it would see a headphone as a problem.) This cap needs a bleeder.
The ground return should go to the '7240's ground pin. If it goes to some random groundy point, the headphone current in the small wiring resistance is liable to make trouble.
The one-output audio level is 4V, which is fine for 150 Ohm phones but too much for common 32 ohm cans/buds. Basically we add a series resistor, 33 to 22 Ohms.
The TG output is mono but cans/buds are usually stereo, we need to feed both HP jack fingers (L and R).
The '7240 chip can drive low-low impedance at either pin, so you "could" feed many friends from the one TG. If you are just using it as a silent practice amp, I suppose that is no use.
(http://i.imgur.com/SenYb2e.gif)
PRR, as always your wisdom is greatly appreciated!
I highly doubt I'll ever use anything but a pair of Sony MDR 7506 cans, which are 63 ohms... does the math still work out? If so, 22r is pretty specific, could I get away with a pair of 10r in series for each lug of the stereo jack?
Design headphone jacks for "any" impedance. Today you have 63 Ohms, many cans are 32 Ohms, some 16 Ohm, and some very fine cans are 100-300 Ohms.
> 22r is pretty specific
If you read, I did say "33 to 22 Ohms". 10 Ohms is pretty risky on lower-Z phones and this much voltage, IMHO. 47 Ohms is fine if you do not require Very-Loud in low-Z phones.
Ah, I meant two 10 Ohm resistors in series on EACH lug of the stereo jack, for 20 Ohms per side, but I'll just go ahead and get some 47 Ohm resistors and be done with it.
My main issue now is with design: trying to figure out a way to wire up a switching jack so that the plugging in headphones will mute the output from the speaker, but I don't think that's going to fly with this arrangement. I guess I'll just wire up a switch to go back and forth... thanks again for the help!
> a switching jack
Very difficult. There is a jack which will do it but more expensive than a switch, or just un-plugging the device not in use.
I have put together tiny giant using verified vero board on this forum, but I am at a lose for why it is not working. Here are volts of :
tl072
1=5.84
2=5.82
3=5.95
4=0\511.64
6=11.24
7=11.23
8=11.64
tda7240a
1=5.51
2=5.48
3=5.43
4=0
5=5.49
6=11.64
7=5.54
when I audio probe the signal, there is a signal going to the speaker out plug but not enuf to drive speakers, the signal will play thru an amp, but to clarify it does not drive speaker cab. When I plug into cab I here total silence. Ideas?
I appreciate any assistance
bump=can any one assist.
Thanks
Vero is notoriously treacherous. Maybe take some pictures of your board and wiring and post them here.
The first TG I built worked great, I have built from the kit 2 addition TG's with no sound, after many hrs of looking for a bad solder connection, wire or ?, I gave up and determined that it must be the IC TL072 or the TDA. So I took the IC and TDA from the non working amps and replaced in my working TG. I determined that both TDA's that came with kit were not working. I get what looks to be correct voltages but the amp are not amplifying the signal. Talor, could you have gotten a bad batch of TDA's? I have order 2 more kits and will let you know the outcome
Thanks for any assistance or ideas.
Quote from: butch199 on February 18, 2015, 02:45:54 PMI determined that both TDA's that came with kit were not working. I get what looks to be correct voltages but the amp are not amplifying the signal. Talor, could you have gotten a bad batch of TDA's?
Hmm, I will discuss this with forum member Waltk who is the one sourcing the parts/putting the kits together. On one hand, in my own experience of building over 1000 electronic doohickies over the years, I don't think I've ever been able to blame a problem on a bad chip. On the other hand, as parts get harder to find, as is the case with the amp chip here, I suppose it becomes more likely that the few you can get could be dodgy. I haven't heard from any others recently that they had this problem, but if anybody else thinks they might have a bad chip, please chime in. If it turns out that there is a bad batch of parts I'll certainly refund anybody affected.
Hey Butch199. The TDA chips that Taylor sells with his TG kits are purchased in batches of 100+ (with many successful builds), so I think a "bad batch" is pretty unlikely.
The TDA7240 has a boatload of on-chip protection built in - however, I've heard of them "going bad", and managed to blow up a couple myself. Unfortunately, once the chip is blown, there's no recovery. So it's possible that something about your second and third builds killed the chips, and swapping them into your first (working) build wouldn't tell us when or how they went bad.
Taylor provides exceptional customer service, and I'm sure he'll help you get back on track. Meanwhile, maybe there's something we can figure out about what happened with these last 2 builds.
Do you have a way to post a picture here? A good high-res picture of your build might tell us something. Also, were there any other differences between your first successful build, and the last 2 that aren't working? Power supply? Enclosure? Wiring/jacks? Did you verify that neither the speaker output terminals are grounded?
-Walt
Walt;
I agree, Taylor has been great and I use my successful build to play out. I will take some pics and send them. The voltages all seem normal(as compared to my working amp. When I trace the audio it goes to the speaker out but is not amped. Is there one of the resistors or caps that I should pay particular attention to that could be causing my problem?
Walt and Taylor;
My bad! figured it out, bad volume pot and broken wire haunted me on both builds that were not working.
Thanks for a great project
Glad you were able to sort it out!
Well done! So just to wrap this up, were you able to get both of them working after finding the problem?
correct all is working, I actually got some bad 10K pots from china. 5 out of 10(10k audio pots) were bad ,
I appreciate all of your assistance
Hi, could I use this battery to run the Tiny Giant? If so, any idea how many hours I'd get out of it? Not having to plug it in would be great. I'd bypass the regulator.
DC 12V 6800mAh Rechargeable Li-polymer Li-ion Battery:
http://www.ebay.com/itm/DC-12V-6800mAh-Rechargeable-Li-polymer-Li-ion-Battery-w-US-Plug-Power-Adapter-/261808093692?pt=LH_DefaultDomain_0&hash=item3cf4fa79fc
(http://i1160.photobucket.com/albums/q485/jdansti/0AB0651D-D4B0-46A7-A5F8-BDE5DD767627-12822-00000C36B2650DE0.jpg)
Yep
TG loaded in 4 Ohms, played steady-LOUD non-stop, will drain a 6.8AH battery in around 3 hours.
In more normal playing (some soft passages, breaks, etc), perhaps "all day".
It's not a bad choice.
You maybe can locally find a lawnmower battery of more AH for about the same price, but much heavier and no charger and it will slop acid if mistreated.
I intend to build a battery powered tiny giant too.
I am thinking of using a 12V lead acid battery, which means it starts around 14.2 volts.
Now,
1 - if I keep the lm338, what will it happen when the battery goes under 11volts?
2 - if I remove the lm338, will the amp chip manage the 14.2 volts?
If you only ever want to power it with a battery, I think you're probably better off leaving the regulator out as in the diagram above. The amp chip will have no problem running up to 18v or so.
Hello, I am working on the Tiny Giant, and have a bare minimum of experience with electronics. This is my first attempt to build. I have had a few problems and am working through them as I go.
However, I believe I may have ruined the TDA7240 chip. (I connected power to ground and vice versa on the PCB then plugged it in). I am not as careless as that makes me sound, but no less, I did it.
My trouble is finding a replacement chip. I can't seem to find one through large name distributors, and many I find through eBay and the like are expensive for what it is.
Is there a know alternative? I was looking at LM1875, but don't know what all I might need to consider before determining if this is a suitable alternative.
Thank you for any advice and time.
> 12V lead acid battery.... will the amp chip manage the 14.2 volts?
This IS a Car Sound chip. MADE for "12V" lead battery plus heavy charge/discharge currents. While modern cars rarely hit 14.0V, older cars did. Car regulators fail and put higher voltage. "Load dump" when a heavy inductance (motor or field winding) is cut-off causes short 40V spikes.
Unless your busker-rig has massive chargers, the TDA7240 will be fine right off the battery. (With a fuse, as Jonsuit shows.)
________________
> eBay and the like are expensive for what it is.
Prices I see on eBay run US$2 for one, $15 for ten(!), to $5-$10 higher-price (which may not be better). Considering what is in there, and what it does, $10 is not "expensive" IMO, though I would try the $2 ones because it is not rare and not liable to fakes.
Thanks for your reply, PRR. I adjusted my expectations, and bought 2 for $10 with free shipping. This way I'll have a spare one to blow before finding a new hobby. :)
Having fried one, I got a new TDA chip and have it installed. This seems to resolve one issue, however I have a new problem. I am not getting guitar signal through.
To the best of my limited knowledge continuity looks good as I followed along with the schematic and checked bit to bit.
My adjusted voltage coming in is right at 11.5v
I have 11.5 on pin 8 of the TL chip and I have 0v on pin four, as expected. I am curious about the other values though.
On the remaining sets of pins I am showing around 3.3 at the + inputs, and 1.6 on the outs and - inputs.
I am very new to this and don't really understand how the audio signal works in relation to these other measures, but I feel like these low voltages might be indicative have some problem that corresponds to my not getting audio through?
As a side note I believe my volume pot amplifier and speaker are all working as I can get an amplified hum from holding the volume pot in a certain way and adjust the volume of that hum.
> I can get an amplified hum from holding the volume pot
Input jack wiring error is a very popular mistake.
I've been looking at getting some of taylor's boards for a while, and I have a buddy who's looking at getting his first amp. He got interested when I mentioned this. The plan right now is to build a 1x12 with a matching head. The idea is to house the board and power supply in the head, as well as an eq and a distortion circuit. I read through quite a few pages of this thread and skimmed some more but didnt find anything like what I'm attempting. I know there's an 11v tap on the board and I intend to use it.
Basically my question is how I would go about doing it? Would it be as simple as getting a schematic for a 3 band eq pedal, then wiring the output of that to the input of the tiny giant with both boards sharing a ground? Same thing with the distortion, wire that in before or after the eq with a pre/post volume and a true bypass? Would all 3 boards then share a ground? I don't imagine the difference between 9v and 11v would matter if the components were rated for say 18v
And something I know nothing about, how could I wire a bypass for the distortion switch that would allow it to be foot controlled at some point? Any help would be appreciated.
It pretty much is as simple as that, although that's a tall enough order if it's your first electronics project.
So, yes you'll be connecting power and ground from the amp board to your EQ/dist circuits, and then you'd just connect the output of one stage to the input of the next.
You're right that you won't damage anything on 11v if it's rated a fair bit in excess of that voltage. Depending on the circuits you choose, you may even like the sound of the distortion better at that higher voltage, although it could go the other way. Generally any circuit can be tweaked to get it functioning the same at a few extra volts, if need be.
The footswitch thing can be approached many ways. Maybe the simplest, especially if true bypass is a must, would be to use a DPDT relay. The relay is inside your enclosure and does the bypass switching. The footswitch is just a latching SPDT that connects the relay's coil to power when the footswitch is pressed. This lets you connect the footswitch to the amp with just a regular mono 1/4" cable that you would already have if you play guitar/bass.
There are some relay bypass kits available, maybe somebody else can pop in with a recommendation for one.
Taylor, we've had the TG for some time now and it's really Great !!! ( JMHO)
Question is , can we adapt the circuit to amplify a Piezo pickup .....do we need some kind of Z buffer ...???
Great, glad you're still enjoying the TG!
You could connect the piezo straight to the amp input, but the sound will not be great. Piezos sound best going into a very high impedance preamp. Connected to a regular instrument input, the piezo forms a highpass filter with the the input and all the low end is removed, leaving a tinny, brittle sound.
Here's a piezo buffer that would work. I built one of these years ago for an electric upright bass I used to have. This was before the TG existed, so I never used them together, but I recall having good results with the buffer going into a tube amp.
http://www.scotthelmke.com/Mint-box-buffer.html
Taylor , THANKS !!! Just like what we were looking for !!! Much appreciated ... !!!!
I bought a board awhile back, finally got around to testing it. Doesn't work.... I have around 11.5 at the regulator and power amp supply pin. My meter is slow but i'm showing 300-400mv to the power amp input when I strum. So the TL072 is working. The thing I can't figure out is, there is 20-30M ohms between ground and speaker jack terminals. I don't have this in an enclosue so it is something on the board. At this point I can only assume the power amp is fried/shorted. Any other ideas?
Also realized the power supply I grabbed is only 2A. I'll use a different one but can't think that would matter for a short test?
The power supply is probably sufficient. Did you get the parts kit too or did you supply your own components?
I just measured my TG and had around 8k and 400 ohms, respectively, from each speaker jack terminal to ground. I'd be out of my depth speculating as to why they're not approximately equal, but yours being effectively infinite resistance in comparison definitely would seem to point in the direction of a problem at the TDA7240.
You mentioned no enclosure, do you have heat sinks on the amp chip and regulator, and are they electrically isolated from each other?
The TDA7240's outputs don't go to-ground. Only to each other. Conceptually they could be infinity from ground, but that's certainly wrong. There will be at least the internal NFB resistors from each output to a groundy inside node.
One reason for a "difference" is that there are parasitic diodes everywhere in a chip. If you flip the ohm meter leads you may get a different reading.
But my first guess is bad connections, at chip, PCB, or jack. Get it out in the light and eyeball those solder joints.
I've got through 10 or 15 pages reading, looking for pics, etc. So, if the answer to my question is in one of the pages I skipped, please don't be too upset with me. I'm a bedroom player with no interest in playing in a band. I've got a Line 6 Pod XT Pro that I intend to use and I want a simple, low power amp that can cleanly get loud enough to be annoying. How loud can these little amps get before starting to distort? I'd like to get two and have two 10" or 12" speakers. I've got some experience with a DIY ham radio, so doing a kit like this isn't foreign to me.
It gets pretty darn loud for playing in a house without an audience. Two sounds like a lot to me if I wasn't trying to be heard over a drummer, but we probably all have a different definition of "annoyingly loud" ;)
I play bass, modular synth, and electronic drums more than guitar, and have used the TG for those purposes quite a lot. Those would all be more demanding in terms of clean power than guitar because of the frequency ranges involved.
What about one amp and two speakers? Would that cause any problems? Not sure whether the output jacks should be parallel or series.
One amp, two speakers would be fine. Parallel/series would depend on the impedance of the speakers you use. You want the total impedance at 4 or 8 ohms generally (check the build document though for details). So if you have two 16 ohm speakers then wire them in parallel for 8 ohms total, etc.
Taylor, I did buy the kit. So the isolators are used between the heatsink. I did try and reflow all the joints to no avail. I just ordered a couple more 7240's so I'll just try and replace it. keep ya posted! thanks for the help
I ordered two of them, just in case.
Noob here, having trouble with my TGA.
I bought the kit, so have all of the appropriate spacers/electrical insulation.
The power supply I found is actually a selectable supply, with the option of 15V at 6A; I wired the amp center positive because the connector for the PS is actually 2.1mm.
I double checked before powering up that the 338 is electrically isolated from ground, as well as both poles of the speaker outs. I'm getting 11.6V at pin 8 of the TL072. It's in a Hammond 1590BB enclosure with the chips heat-sinked into the side.
When I fired it up, I got about 1 second of a clean sounding guitar chord before it fuzzed and farted out. If I mute the strings and wait a few seconds, I can get another second of clean before fuzzing out.
Any ideas?
The symptoms sound like the amp chip overheating, but from your description it seems like you've got your bases pretty well covered on that front. Could you post a picture of the guts? Might help spot something that's keeping the enclosure from doing a good job as a heat sink.
After it cuts out, does the amp chip feel really hot? (Obviously, use standard "touching a thing that may or may not be really hot" procedure for safety's sake)
https://dl.dropboxusercontent.com/u/23281298/IMG_3328.JPG (https://dl.dropboxusercontent.com/u/23281298/IMG_3328.JPG)
https://dl.dropboxusercontent.com/u/23281298/IMG_3329.JPG (https://dl.dropboxusercontent.com/u/23281298/IMG_3329.JPG)
Sorry, tried to link the pics themselves but they were massive, not sure how to reformat them on this board. The reason some of the solder joints look odd is that I trimmed them down significantly to remove excess wire (despite the huge enclosure, vertical space is actually pretty tight), but looking over the joints none of them are loose or dull. As an aside, since I mentioned that space is tight, the dysfunction I describe happens while the lid is off, so that's not shorting the chip.
The amp chip is specifically the 338, right (sorry, as I said, I'm quite new to this)?
The chip stays cool even once it starts to fart out and go mute. It only takes a second before it starts to cut out, then it's completely quiet, not even the usual 60 Hz hum getting through. If I mute the strings and wait 3-5 seconds, I can begin to hear the usual slight background noise, then can play a few notes until it fuzzes out and dies again. I get essentially no real time of significant consistent sound, and the chip isn't warm to the touch in the slightest. Seems like it should take longer to heat up/cool down?
I'm happy to entertain other thoughts. I bought two kits at one time so I can always try replacing the 338 chip and seeing if that solves the (short-term) problem, though I'd prefer to see if there are other trouble shooting options before pulling it apart.
Thanks again for your help! I'm excited to get this working, I built it inside a larger enclosure with the eventual goal of adding EQ and gain stages if I can get them all in there.
can I suggest: measure the supply voltage, while good running and stop running. does it change when the sound goes? is it possible the supply is overloaded/ing and doing a sputter shutdown?
Sorry, summer has been nuts and crushed my productivity, just got around to this.
Checked the supply voltage while testing the amp, stays stable at 15V without fail.
Could I have fried the chips while soldering them in? The TL072 is socketed but I didn't socket the LM338T or TDA7240A (I don't think they would have fit in the enclosure if I did). Or is it more likely a capacitor that's not working (like it can't hold it's charge appropriately?)? I checked all of the resistors before installing them but can't remember if I checked all of the caps.
Any further help appreciated!
It sounds to me like the amp chip (TDA7240, the one with 7 legs) is going into its automatic protective shutdown. I don't think it would work even for those few seconds if the amp chip was damaged, and if you're getting steady voltage then you know the regulator (338) is fine.
One thing you didn't mention: what sort of speaker are you connecting to it? Impedance? Can you check the speaker pads on the board with a multimeter to see if one is somehow getting shorted to ground?
Hello All,
I come seeking help with my Tiny Giant. I new to this forum and new to electronics for that matter. I have built a few projects and I am hooked, but still getting my head around some of the basics.
So, I bought the Tiny Giant kit and put it together. When I fire it up I get no signal - but - if I jumper the input jack directly to the in of the volume pot I get sound out the speaker. So if I skip everything before the volume pot including the TL072, it sort of works. Its a little scratchy because the jumper connections are poor. The standby toggle works and I ultimately get sound, either a hum or the guitar if I use the jumper, so I believe the TDA7240A is working properly.
I tested the leads on the TL072 and this is what I got:
1: 0
2: 0
3: 3.95v
4: 0
5: 3.95v
6: -0.05v
7: -0.01v
8: 11.75v
I also confirmed that I didnt have the 10uf cap in backwards.
Any help is appreciated.
Thanks.
The bias voltage at pins 3 and 5 looks a little off. It should be around half the regulated supply voltage, so closer to 5.8 or 6V. Check the two 1M resistors to make sure they're the right value and there aren't any solder bridges to adjacent parts.
Other than that, it looks about right, so you may just have a cold solder joint around the input, like the 100N cap right by the volume pot pads. Often just reflowing all your solder joints (reheat, allow to cool without letting the parts move) can solve problems like this. Also, apologies if this is too obvious - it can get the best of us - but make sure the TL072 is in the socket the right way round - the notch or dot near one end of the part should be facing towards the 100N and 220N caps.
Hello everybody. First of all thank you for the great posts and information. I have built my tiny giant and I get a very low volume on a 8ohm speaker. Barely audible. Before I get to measure things maybe somebody can take a look at my built and see if there is something clearly wrong. Any input would be much appreciated. Thank you.
https://drive.google.com/file/d/0B_EO7EHMDw6XMFpaaDEzSXNqbFU/view?
https://drive.google.com/file/d/0B_EO7EHMDw6XVkpEWVpFQVBKQ2s/view?usp=sharing
https://drive.google.com/file/d/0B_EO7EHMDw6XNWYzRkhnODFtRmM/view?usp=sharing
How about a picture of the bottom. Some of your solder joints don't look very good.
Thanks. Here is a pic of the back and off board wiring. Also, the amp makes a loud buzz when I touch the volume.
https://drive.google.com/file/d/0B_EO7EHMDw6XNDBJZ2o0ekxXbzg/view?usp=sharing
https://drive.google.com/file/d/0B_EO7EHMDw6XTkx2d1pvZUM3cGs/view?usp=sharing
Might be a good idea to scrub the bottom of the board with rubbing alcohol - your solder probably has no-clean flux (though you should check if you don't know for sure - I once had a month's worth of projects not working because of this) but there could be bits of solder in the flux shorting things together.
Also, possible short on one of the 22uf caps?
There's one part where it looks like the pad got overheated and pulled up (pic 5, bottom right). This is OK because that part doesn't connect on the bottom, but make sure there's some solder connecting it on the top.
Thank you for the reply. I have scrubbed the PCB, nothing. The burnt spot has some good solder on the other side so that's no problem. Do I have to take the caps out to test them?
I would recommend just reflowing all of the solder joints (heat them back up and let them cool without moving the part/wire). Then measure voltages with your multimeter on all the pins of the 3 ICs while the TG is powered up, and post them here.
You probably don't need to test the caps, just make sure that the 22uf cap farther from the edge of the board is not shorting its two contacts together. In your picture there looks like a possible a solder bridge.
You didn't mention or show a heat sink or enclosure, but you've got those, right?
Thank you! I will do that! Be posting asap.
Question for Taylor, or anyone else: I am putting together an order at Tayda, getting ready to tackle a few long awaiting projects, so the question is what heat sink (x2) would be sufficient? Here is the Tayda heatsinklink (https://www.taydaelectronics.com/hardware/heatsink.html). I haven't really settled on an enclosure yet, so I'd like to be able to dissipate enough heat regardless. TIA for your thoughts.
Ben
I used one of those extruded aluminium enclosures and bolted the power amp chip to it. Gets mildly warm.
Paul will be along shortly to advise you how to do the maths to work this out correctly! :)
Hey, Marc, you mean one of the little ones? (or two of them, I guess--one for the regulator, too) That's really my question, I guess--would those small ones (17mm x 17 mm x 26 mm or so) do.
I built mine way back when to use the enclosure it's in as the heat sink - it's a 1590A. But, I've never tried to gig with it, so that might be insufficient for playing with volume up fully for a long set. I wouldn't use one of the smallest ones on that page. Maybe one of the 14 fin ones, since they're all pretty cheap.
When I first built it, I bought an absolute monster heat sink - about 11 x 9 x 2 inches. That was absurd overkill, but some day I'm going to find a purpose for that thing. It makes a lovely bell sound if you suspend it on a string and hit it with a hammer.
Quote from: Ben N on February 15, 2017, 10:38:25 AM
Hey, Marc, you mean one of the little ones? (or two of them, I guess--one for the regulator, too) That's really my question, I guess--would those small ones (17mm x 17 mm x 26 mm or so) do.
I meant this kind of thing - an enclosure, not a heatsink:
(http://info.ee.surrey.ac.uk/Teaching/Labs/images/Hammond%20esque.jpg)
Quote from: Taylor on February 15, 2017, 01:25:43 PM
When I first built it, I bought an absolute monster heat sink - about 11 x 9 x 2 inches. That was absurd overkill, but some day I'm going to find a purpose for that thing. It makes a lovely bell sound if you suspend it on a string and hit it with a hammer.
ahhh, the stashed heatsink. how many of us [older types] don't have at least one big heavy heatsink 25 or more years old, "I might use in an amp one day"?
Quote from: duck_arse on February 16, 2017, 08:39:17 AM
ahhh, the stashed heatsink. how many of us [older types] don't have at least one big heavy heatsink 25 or more years old, "I might use in an amp one day"?
That reminds me, I have a couple of old desktop computer power supply cages with fans that I always figured to stick something like a Firefly in--the Tiny giant could go in one, although it does seem kind of overkill.
Anyway, thanks, everyone. I think I will order a couple just to be safe, and, as Taylor says, because they are so cheap.
Quote from: duck_arse on February 16, 2017, 08:39:17 AM
ahhh, the stashed heatsink. how many of us [older types] don't have at least one big heavy heatsink 25 or more years old, "I might use in an amp one day"?
Nah man, I'm
totally gonna get around to using this thing... ;)
(http://i.imgur.com/Wlf7eSc.jpg)
Edit: Y'know, I was being facetious, but I just noticed there are 4 sets of holes spaced just right for the TG. Since I'm into modular synth stuff these days, a quadraphonic amp is something I could actually use. I could finally experience electro-fart noises
whirling around me.
you would have to paint it, black (you devil!) if you wanted to mount four amps on, just to shift the heat.
What kind of foot switch would I need in order to turn this thing on and off without having to bend over?
Quote from: KF5TJC on March 05, 2017, 04:33:24 PM
What kind of foot switch would I need in order to turn this thing on and off without having to bend over?
Just a SPST latching foot switch to break the power. If you've got a DPDT or 3PDT, those would work too, you'd just have extra poles that wouldn't be used.
exists PCB for transfer?
This PCB is double-sided and not the type of layout that could be etched at home, but the schematic is available on the musicpcb site.
I'm wanting an on/off switch with an led. Would I jumper where the standby switch would normally go and just put a 3pdt switch in between the ac jack and pin 6 on the tda7420 chip? Just wire the led and resistor in parallel?
Just leave the standby pads empty, and then put your switch between the power jack and power inlet on the PCB. Then I'd take the power for the LED from the regulated voltage pad near the TL072 - check the build doc for a drawing.
Got mine built today. Things didn't work out like I'd wanted with the on/off toggle and led. The push button doesn't work either. So, my amp is always on. I mounted it to the side of my cabinet to keep it handy but out of the way. I ordered two at the same time, so I still have one left to build. Someday, I'll either do another one or rehouse this one in a better enclosure that looks a little better.
(https://s7.postimg.org/68ej34sl3/image.jpg) (https://postimg.org/image/68ej34sl3/)
(https://s7.postimg.org/lieeabo3b/image.jpg) (https://postimg.org/image/lieeabo3b/)
(https://s7.postimg.org/5y70jsdyv/image.jpg) (https://postimg.org/image/5y70jsdyv/)
(https://s7.postimg.org/hoky166rb/image.jpg) (https://postimg.org/image/hoky166rb/)
(https://s7.postimg.org/azeel5lfb/image.jpg) (https://postimg.org/image/azeel5lfb/)
Hi,
I'm fairly new to the DIY world and I've just build a few pedals from kits and recently my first veroboard following tagboard blog layout.
I really want to build this tiny marvel but I have a big dilemma, I live in Europe and the shipping cost for the PCB from taylor is higher than the board itself (13$), it really bothers me.
So I found a veroboard layout on tagboard http://tagboardeffects.blogspot.fr/2014/06/tiny-giant-amp.html
The problem is that the regulator and the amp are not aligned like on taylor pcb, so I can't screw them on the side of the enclosure for heat dissipation.
Can you link me some valid heat sinks that I could use ?
Is there anything in this list that will fit the purpose ? https://www.musikding.de/navi.php?qs=heat+sink
In the case I use separate heat sinks I do not need the insulator, I can just screw the chip on the heat sink. is that right ?
Another question, I'd love to wire an accutronics spring reverb tank to the circuit, reading the thread someone did it, but how ?
I suppose I need to cut the rca plugs and solder the wires somewhere on the circuit, and add another potentiometer, can you guide me through the process pls ?
Thank you very much
I there, if I use a 12VDC@5A power supply I guess I can omit the 338 and it's 2 resistors and capa ?
Yes
Thanks !
Quote from: Taylor on March 19, 2012, 06:58:04 PM
Pin 5 is actually connected to pin 3 and therefore driven by the input signal and biased to the center of the power supply. That opamp is not being used and this is just a way to hold it near the center of the supply to avoid drawing a lot of current.
So, that's a mistake in the schematic. There was an error in the voltages at one point, which I corrected, but it looks like in correcting that I created a new error. In other words, there should NOT be 11.6 at pin 5.
I don't see anything obviously wrong in your voltages, so my guess is that there is just an open circuit somewhere in your audio path. I would recommend audio probing to see where the signal is getting stopped.
Hi Taylor, would you mind clarifying in you schematic the pin numbering ?
This is my guess but since you say that there should not be 11.6v at pin 5, which is actually connected to pin 3 I must be wrong
(http://nsa39.casimages.com/img/2017/10/18/171018054739998721.jpg) (http://www.casimages.com/i/171018054739998721.jpg.html)
That would help me a lot
Thanks
Pin 8 is the power for the TL072, so that's the only one with 11.6V on it. The opamp at pins 5, 6 and 7 is the one being used as the "preamp" before the TDA7240A power amp. As Taylor says, pin 5 is also connected to pin 3 - the non-inverting input of the other opamp on the chip - to bias that opamp, which is otherwise wired as a buffer (pin 1 connected to pin 2) but unused.
Thanks bluebunny, I did the modification on my build (on veroboard from my own layout), that didn't change anything but at least now I know it's correct :icon_wink:
I still have an issue, when the volume pot is cranked, it seems the chip gets overloaded, notes attack sound farty but become normal when I let ring. If I push it with an overdrive in front, I don't have this problem and it sounds great, I mean really great, and loud !
If I don't go over about 50% on the pot course, no problem and nice clean sound, very well balanced. But I want volume
I built it without the 338 and its resistors and cap because I power it with a 12v@5A PS
Any idea ?
I don't know if this is going to help, but in my case I had farting noises due to the improper cooling of the chip. What kind of heatsink do you use?
Quote from: potul on October 20, 2017, 06:05:50 AM
I don't know if this is going to help, but in my case I had farting noises due to the improper cooling of the chip. What kind of heatsink do you use?
Pics of my build
(http://guitar-fx-layouts.42897.x6.nabble.com/file/n40203/IMG_6902.jpg)
(http://guitar-fx-layouts.42897.x6.nabble.com/file/n40203/IMG_6904.jpg)
(http://guitar-fx-layouts.42897.x6.nabble.com/file/n40203/IMG_6905.jpg)
And my power supply, which I modified to make it 2.1mm center negative
(http://guitar-fx-layouts.42897.x6.nabble.com/file/n40203/IMG_6906.jpg)
Ok, heatsink seem to be enough...
Just to be sure, you could try to force some cooling (using a fan pointing to the heatsink), and see if this reduces the farting.
I can try that but the problem starts with the first note when the chip is still cold
Farty sounds like mis-biasing. Double-check the two 1M resistors at the input to the opamp.
Edit: actually, scratch that: I hadn't spotted your comment about driving with an overdrive pedal. :icon_rolleyes:
ok I solved the problem by lowering the regulator output voltage down to 9V using a 160 ohms resistor intead of 120.
Now the amp works like a charm, sounds very good on all the volume pot course.
I'm gonna try a bright cap on the volume pot to try to avoid losing highs at low volume. Has anyone already tried that with this amp ?
The bright cap did nothing so I socketed the 100n input cap and that was a great improvement.
I'm used to bright amps (my band amp is a Vox AC15) so I tried a few values and was very happy with 47n at full volume and 1n at low volume.
I'll put these two caps on an dpdt switch and that will do the trick :icon_smile:
No it's time to put all these wires and components in a nice tiny enclosure :icon_wink:
Cool. Remember to make sure your speaker output jack is completely isolated from a metal enclosure and isn't connected to ground. Then we need pictures, of course. :)
Sure will :icon_wink:
Where's everyone getting the TDA7240? I can't track a local (Canadian) supplier, just stuff out of HK via ebay.
Sent from my P01Z using Tapatalk
Also, a noob wuestion...but could one rig up a send/return fx loop on this kit? If so, how?
Thanks in advance.
Sent from my P01Z using Tapatalk
For an effects loop, if you're building from my PCB, you can tap the "send" from the volume knob pad number 3. Depending on what kinda stuff you might put in the loop, you may want to add an extra opamp buffer on the "return" which would be volume knob pad 2.
Quote from: Taylor on January 30, 2018, 10:01:38 PM
For an effects loop, if you're building from my PCB, you can tap the "send" from the volume knob pad number 3. Depending on what kinda stuff you might put in the loop, you may want to add an extra opamp buffer on the "return" which would be volume knob pad 2.
Thank you !
Sent from my P01Z using Tapatalk
Quote from: Taylor on January 30, 2018, 10:01:38 PM
For an effects loop, if you're building from my PCB, you can tap the "send" from the volume knob pad number 3. Depending on what kinda stuff you might put in the loop, you may want to add an extra opamp buffer on the "return" which would be volume knob pad 2.
Thanks again for this. Another question - is it intended that the TL072 be soldered to the PCB or mounted in a socket?
Update-- scratch that. Found it on the list of parts for the complete kit.
Sent from my P01Z using Tapatalk
Quote from: pmac11 on February 03, 2018, 06:17:27 PM
Quote from: Taylor on January 30, 2018, 10:01:38 PM
For an effects loop, if you're building from my PCB, you can tap the "send" from the volume knob pad number 3. Depending on what kinda stuff you might put in the loop, you may want to add an extra opamp buffer on the "return" which would be volume knob pad 2.
Thank you !
Sent from my P01Z using Tapatalk
The full kit wasn't available when I ordered, just the PCB. I've purchased all the components and am ready to build.
Before I get underway, I'd like some clarification regarding isolating the regulator chip. I plan to use the aluminum enclosure as the heat sink...so how do I physically connect to the enclosure for heat dissipation while maintaining electric isolation?
Thanks in advance!
Sent from my P01Z using Tapatalk
You will need a silicon pad and a washer. Something similar to this:
https://www.amazon.com/Silicone-Heatsink-Insulator-Insulating-Particles/dp/B00KV6P828 (https://www.amazon.com/Silicone-Heatsink-Insulator-Insulating-Particles/dp/B00KV6P828)
(https://images-na.ssl-images-amazon.com/images/I/51Sqw5XULxL._SL1024_.jpg)
(I didn't verify if the size is the one you need)
Mat
Quote from: potul on February 16, 2018, 02:29:03 AM
You will need a silicon pad and a washer. Something similar to this:
https://www.amazon.com/Silicone-Heatsink-Insulator-Insulating-Particles/dp/B00KV6P828 (https://www.amazon.com/Silicone-Heatsink-Insulator-Insulating-Particles/dp/B00KV6P828)
(https://images-na.ssl-images-amazon.com/images/I/51Sqw5XULxL._SL1024_.jpg)
(I didn't verify if the size is the one you need)
Mat
Sweet. Thanks!
Sent from my P01Z using Tapatalk
So does the Tiny Giant need a preamp with a tone control in front of it?
Sent from my P01Z using Tapatalk
No, you can plug a guitar in directly. Having said that, I've tended to have a couple of pedals in the path. And having said that, I'm sure I've used it naked with an acoustic too (the signal path, not me... :icon_redface:).
the Tiny Giant already has a preamp, with sparkling clear high-impedance input - the TL072. It can be nice to hear nothing but your pickups coming out of a speaker.
Quote from: bluebunny on February 20, 2018, 02:50:59 AM
No, you can plug a guitar in directly. Having said that, I've tended to have a couple of pedals in the path. And having said that, I'm sure I've used it naked with an acoustic too (the signal path, not me... :icon_redface:).
Lol, thanks!
Sent from my P01Z using Tapatalk
Quote from: garcho on February 20, 2018, 10:24:32 AM
the Tiny Giant already has a preamp, with sparkling clear high-impedance input - the TL072. It can be nice to hear nothing but your pickups coming out of a speaker.
Thanks!
Sent from my P01Z using Tapatalk
Nice amp.
Going to try to build a combo with an 8" bulldog from a Vox pathfinder. :)
Hi all.
I'm trying to assemble the circuit using a breadboard, but because of my near-zero electronics knowledge, i'm struggling with the TL072 layout.
Can anyone tell me if Keeb's thoughts are correct?
Quote from: Keeb on March 19, 2012, 07:15:54 PM
But just for my own understanding, am I correct in thinking that the U1A part is pins 5, 6 and 7 making the U1B pins 1, 2 and 3?
I'm used to thinking of opamps as a record, "A" being the first side (1,2,3,4) and "B" being the second side. That's why I'm asking.
I can't figure out where to connect what, because i really don't know how to identify the chip's pins in the circuit... :(
Thank you for any help :)
Edit: I also noticed that i don't have any 2,2 ohm resistor... Could 2,6ohm do the trick? ???
Most dual opamps - like the TL072 - look the same. Here's one image grabbed at random from Google:
(https://www.soundtronics.co.uk/images/detailed/23/Ext-2240-082.jpg)
The + and - (non-inverting and inverting) inputs are clearly shown for each of the opamps.
I can't imagine using 2R6 vs. 2R2 will cause any problems. Try it out - no-one will die. :)
Thank you for your help.
I'll try it out and see what happens. :)
Not forgotten, but having a hard time building it. :icon_mrgreen:
Disassembled it and trying again...
Am I correct?
When using a different voltage supply than 19,5V.
I need to adjust the resistance (1K original) connected to leg 1 (adjust)of the LM338?
Perhaps a trimpot to make it a bit easier?
greetings
As far as I know you don't need to adjust anything. The adjustment is needed if you want to provide a different voltage to the circuit (output from regulator)
the voltage should be:
Vout = 1.25 (1+R2/R1) = 1.25 (1+1000/120) = 11.6666
which does not depend on Vin if you get a high enough voltage.
FYI, I'm powering mine with 12v bypassing the regulator.
I finally got around to putting my Tiny Giant Kit together after it sitting in its little yellow envelope for the past 8+ years. I made a mistake soldering in a resistor and borked up the pcb when I desoldered said resistor and solder stayed in the mounting hole which I couldn't remove. I truly borked up the PCB when I tried to drill out the hole!
I have a stack of perf board lying around and all the components from the original kit (including the now desoldered transistor!). I remember that Taylor said he had a perfboard layout when he was prototyping. Is this perfboard layout available? I could put together a layout myself, but I don't want to reinvent the wheel if one already exists.
Tim
Welcome to the forum, Tim.
I've not seen any perf layouts, so I can't help you there. Be aware that the amp chip has pins which don't fit on a regular 0.1" grid, so you'd need to bend half the pins to fit. So far as dealing with a PCB hole filled with solder, just heat the pad with your soldering iron and poke though a cocktail stick while the solder's still molten. No need for a drill. :)
I use a steel needle to open clogged holes. Heat, poke, done. Hot solder won't stick to cold steel.
If you have only borked a few holes and traces, it is surely easier to stick with the PCB and patch-up. If a hole-pad is gone, extend the part lead or a jumper wire to the next healthy part of the trace.
I never thought this guy would turn up here.
(https://si.wsj.net/public/resources/images/BN-SJ285_mcgurn_GR_20170306164236.jpg)
Quote from: Ben N on July 28, 2020, 08:01:37 AM
I never thought this guy would turn up here.
(https://si.wsj.net/public/resources/images/BN-SJ285_mcgurn_GR_20170306164236.jpg)
Wrong Bork!
Thanks for the tip re: using a hot needle to free up the solder pad/well. I'll see if I can salvage the PCB. If I can't I'll plan out a perfboard layout.
Thanks again
Tim
> using a hot needle
I use a hot soldering iron and a cold steel needle.
A hot needle, if it cools a bit, will freeze solid in the hole.
Hi, I know this is an old thread, but I'm hoping maybe Taylor will see this. I just found the Tiny Giant amp and built it. It's working for the most part, but if I turn the volume knob up half way or more, all of a sudden the speaker starts vibrating and freaking out until I dial it way back again. I checked and I have 14.6VDC coming into the amp. No grounding on the LM338T or the speaker jack and I use a 1.2K resistor, so I'm getting about 13.8V on pin 8 of the TL082 (I used TL082 because I didn't have a TL072). Anyone have any ideas of why this happening with the amp?
Anytime an audio amp freaks-out at high volume, suspect that the output signal is leaking-back to the input circuit.
Taylor's PCB and suggested wiring? Perfboard and haywiring?
Photos?
Yes, Taylor's PCB and suggested wiring. The only addition was I added a TMB tone control between the input jack and In on the board. I'll try and post some pictures later. What would be the best way to check to see if the output is leaking back to the input?
Could it be the input jack wires crossing near the speaker wires? Or possibly even regular old acoustic feedback from the speaker to guitar?
I would take that tone network out for the moment. That's a lot of parts/area to catch signal from speaker wires.
Just got back from traveling for the holiday. Haven't had a chance to take pictures yet, but yes, the wires going from the board to the speaker definitely cross the input jack wires inside the enclosure. Didn't think it would cause an issue. I don't think it's the acoustic feedback. I'm actually using this as a preamp for a Leslie speaker and so the speaker is fully enclosed. I also tried it with just a bare speaker that had lying around thinking maybe it was a problem with the impedance of the speaker. I'll try re-routing the speaker wires to keep them away from the input wires and see if that helps. Is there a way to isolate or insulate the input wires to keep from picking up signal from the speaker wires?
You could try using screened wire for the input (connect the screen to a suitable ground point at one end only), but you'll probably find re-routing the input and output wires away from each other will be more effective (and quicker).