Alrighty, my background in electronics (outside of residential 120/240V wiring) is primarily related to Arduino. I have a fairly decent stockpile of [cheap] support components that I'll list at the end of this post
I have no specific projects in mind, but as I'm a casual guitar player, fiddling with DIY pedals sounds like a good activity to keep myself entertained over the winter. I suspect drive/fuzz/distortion and tone effects to be the likely candidates that catch my interest.
As the topic states, I'm looking for a bit of advice regarding what I should include when I place an order from DigiKey. I took a quick flip through various schematics and came up with a short list of ICs I might order. I recognize that some of these are similar, but I'm not well enough informed to understand if they're interchangeable... Does anyone have any comments about this list? Can anyone suggest [other] components I might want to have on hand?
LM386N, TL022CP, TLC2262CP, NJM4558D, RC4558P
Thanks a bunch in advance to anyone who replies!
And here's what I have on hand...
4pcs TDA2050 Audio Amplifier board
4pcs LM1875 Audio Amplifier board
4pcs HW-404 Digital Audio Amplifier board
2pcs NE5532 Audio Amplifer board
3pcs USB/BT Audio player board
1pcs USB Audio player board
8pcs XL6009E1 Buck/Boost board
50pcs LM393 [various] sensor board
2pcs Arduino Pro-Mini
2pcs Arduino Uno
3pcs 2x16 I2C LCD display
1pcs 1" 12C LCD display
1pcs SM-PLF12B 12V 1A power supply board
1pcs 3V 1A power supply board
300pcs Ceramic capacitors; 30 values, 2pF-0.1uF (brown)
600pcs Ceramic capacitors; approx similar similar values as brown ceramics (blue)
300pcs 16V electrolytic Capacitors; similar values as brown ceramics
300pcs Film? capacitors; similar values as brown ceramics (green)
50pcs Film? capacitors; 4 values: 250/400V, 105/155J (brown)
200pcs 10-24V Electrolytic capacitors; 20 assorted values
1000pcs 50V electrolytic capacitors; up to 2200uF
300pcs Film? capacitors; similar values as brown ceramics (yellow)
1000pcs Various value; 1 watt resistors (big blue)
2000pcs Various value; 1/4 watt resistors (little blue)
1000pcs Various Thermistors (big brown)
100pcs Various 2/3/4 pin connectors, pins, etc
900pcs npn/pnp transistors; 50pcs, 18 types
25pcs IRF244N N-Channel MOSFET
200pcs 1N4xxx Diodes
200ocs 1N1007 diodes (1A, 3W)
50pcs 1N5402 Diodes (200V 3A)
300pcs 1N47xx Zener Diodes (3-47V)
100pcs 9.1V 1W zener diodes
40pcs DB107 rectifiers
50pcs neon indicator lamp
100pcs assorted 2mm LED (coloured plastic)
100pcs assorted 5mm LED (coloured plastic)
100pcs assorted 8mm LED (clear plastic)
100pcs assorted 5mm LED (clear plastic)
8pcs B5k potentiometer
8pcs B10k potentiometer
8pcs B20k potentiometer
8pcs B50k potentiometer
8pcs B100k potentiometer
8pcs B250k potentiometer
5pcs B500k potentiometer
5pcs A500k potentiometer
200pcs assorted surface mount switches
100pcs through-hole microswitch
20pcs small isolating transformer
20pcs small chokes
Edit: The requirement to use Google to check how many knobs a random pedal has in order to correct a typo...
:icon_eek:
Nice list. I'd just order some stuff for say, 4 or 5 specific pedals that you DON'T have, and go from there, LOL!
- Some JFETS....2N5457, and J201 IF you can find them
- Mosfets...BS170/2N7000
Your opamp list looks great for starters. Perhaps a few NE5532's. MOST dual opamps are interchangeable, not all, check pinouts on data sheets...some don't give 'as good' performance if you swap...many that use 4558 (a "lesser opamp") actually sound sterile and crap if you put in TL072, for example!
Might want a few PT22399 delay chips (they're cheap) to play around with
Maybe: a few metal enclosures with 1/4 mono and stereo jacks from Smallbear electronics to connect your 'stuff' to your guitar and amp. A few 3pdt stomp switches too, of course. A couple of 1M pots are always needed.
Some perfboard for 'quick dirty PCB construction'
You must have breadboards and jumpers already? If not, get some
Since you seem 'in deep', perhaps make a power supply / "Breakout box" to power breadboards which has in/out jacks and bypass switching...build a station for BB and modding stomp stuff...
Welcome to the forum! Always glad to see new faces around here, let us know what you're working on!
Hi & Welcome.. :icon_wink:
I don't see any A100k pot so put some of them in your list..
P.S.
>1000pcs Various Thermistors (big brown)<
I'm puzzling over for 1000 implementations in pedal world.. :o
Maybe some kind of LDR equivalent, perhaps..??
Colour me impressed; 2 of 2 useful replies inside of a couple hours.
Quote from: antonis on November 22, 2022, 03:48:34 PM
I don't see any A100k pot so put some of them in your list..
Good call - should probably order
Quote
>1000pcs Various Thermistors (big brown)<
I'm puzzling over for 1000 implementations in pedal world.. :o
My collection of components was purchased for non-pedal purposes, I suspect that your confusion is correct and that there isn't one! ;)
Quote from: GibsonGM on November 22, 2022, 01:49:50 PM
I'd just order some stuff for say, 4 or 5 specific pedals that you DON'T have, and go from there, LOL!
"where to start" in the endless pile of schematics was my issue! I appreciate the random assortment of components you listed!
Quote
A few 3pdt stomp switches too, of course. A couple of 1M pots are always needed.
Good call regarding the stomp switches, especially being that my cursory research suggests it's effectively impossible to get the type of enclosure I'd prefer... Why are 1M pots always needed? Linear or Log? Nothing came up on Digikey, where might a guy find a PT22399 delay chip?
I do have some perfboard, breadboard, 30V/10A bench supply, Fluke 12E+, offshore true-RMS meter, along with various gauges of wire, jumpers, interconnects, etc. Also have plenty phone jacks and other guitar components. I'll worry about [fabricating] an enclosure if I do end up building an effect I would actually use.
Thanks for the warm welcome and replies, I sense I'm going to like this forum!
I make all sorts of everyday stuff; if anyone's curious I use the same handle on Instagram
Quote from: ThePracticalPeasant on November 22, 2022, 04:24:47 PM
I'll worry about [fabricating] an enclosure if I do end up building an effect I would actually use.
Thats the best part of the fun..!! :icon_wink:
I found a bunch of PT2399's on Ebay, and they proved to be the real thing, tho we do have to be aware of knock-offs. (let me know if you'd like the seller ID on there)
1M is a common value for gain pots and the like, in both opamp and tube circuits. I see both audio and linear tapers being used, tho I think linear is more common. Since you seem to really like parts, I suspect you'll pick up both types :)
This is a fun forum, people like to discuss the hobby and help others, and we generally try to not go out of our way to be snobby or divisive!
Welcome. Some nice woodworking there. Don't think I've seen a pick-up mounted lengthwise along the string before
Quote from: GibsonGM on November 22, 2022, 04:52:06 PM
I found a bunch of PT2399's on Ebay<snip>
Utmel lists it but also lists BU9253 as a substitute; Digikey lists BU9253AS with none in stock but offers TPA5050 and TPA5052 as substitutes, with surface-mount in stock. Has anyone tried any of these other part numbers?
Quote
Since you seem to really like parts, I suspect you'll pick up both types
You know me already! I generally make an effort to have an assortment of parts for my various hobbies on hand. In my years, I've discovered that the best way to kill my motivation is to force myself to drive to a store or wait for a mail order.
Quote from: stallik on November 22, 2022, 05:05:19 PM
Welcome. Some nice woodworking there. Don't think I've seen a pick-up mounted lengthwise along the string before
Thanks! It works fairly well given that the two strings are far enough apart that each gets a coil :)
If you are organized enough actually KNOW the counts of the parts you have you are way overqualified for this hobby... :icon_lol:
That said, I have begun at least 80% of my projects assuming I MUST have all of the parts I need only te be placing the project in a big ziplock bag waiting for a part order.
The most frustrating part of this sport for me is realizing you only need 1 or 2 missing .05¢ components and having to buy enough other crap to fill up a $5.00 minimum order.
The key to happiness though is just enough planning so you have pre-ordered the parts you need for the project you are starting so you can just build, test and play.
and don't forget to order the damn enclosure.... I always forget that...
Quote from: jhaneyzz on November 22, 2022, 06:34:49 PM
If you are organized enough actually KNOW the counts of the parts you have you are way overqualified for this hobby... :icon_lol:
That said, I have begun at least 80% of my projects assuming I MUST have all of the parts I need only te be placing the project in a big ziplock bag waiting for a part order.
LOL, When I originally got into the Arduino thing, I bought a pile of bulk/variety packs of common components because I had no idea what I'd need. Of course that brings up "why buy one 1000 count variety pack of quarter watt resistors when you can buy TWO 1000 count variety packs of quarter watt resistors".
On a related note, it seems that late Sunday evening I did in fact put in a small order from DigiKey [prior to subscribing and posting my question here]. I now have 10pcs of each of the first two items on my list, RC4558P and TL022CP, though given that I was apparently half asleep when I placed the order, I have absolutely no idea what schematic I might have been looking at.
Pretty folks say something about the first thing about having a problem...
good thing I don't have a problem, or my memory would be one...
Edit: Figured out the order when Fed-Ex just dropped a package on my doorstep
I bought a couple of those "kits" myself when I first started. I've found I have gone through all the commonly used values for pedals multiple times over and have some I have never touched. I'd agree with what gibsongm said just pick a few pedals and order what you don't have.
That being said this is kind of an interesting list this person compiled to get an idea of what values are common in pedals.
https://diyeffectspedals.com/common-diy-guitar-effects-pedal-components/
Right. Locrian hit on something - you can never have too many 1k, 10, 100k 470k 1meg resistors! That would be a good purchase from Digikey. A 'couple' of the bulk sets will usually take care of the rest (I probably have 3 or 4 of those sets in my little toolbox rat's nest. The most common values I keep in envelopes).
Then the .001, .01, .1 nF poly caps, and 1, 10, 33, 47, 68, 100u electros (I go for NP where possible)...that list Locrian posted probably shows this...you really ARE pretty well-outfitted for jumping in, though, ha ha.
Someone on our street was having a garage sale a few years back and he was offering two reels of through-hole resistors, one of 43K 5% and the other 23.2K 2%. The reels were $2 apiece. Naturally, most of my builds use these values now as I have over a thousand of each. With a lot of designs, you can build around values you have.
I would add some photoresistive cells and LED/phototransistor couples because a photoresistive cell with a few resistors in series and parallel helps make the LED adapt to ambient light - a fixed current setting for a LED that can be seen in daylight is too bright for a dimly lit club, so some variation with ambient light is useful. The LED/phototransistor pairs I am thinking of are used as interrupter counters. They have an LED on one side facing a phototransistor on the other side and have a space in between them so anything that goes between them shuts off the light. They make good switches with a spring-loaded blade between them and a Schmitt trigger on the output to avoid dithering between states.
Vactrols, which are LED/photoresistor pairs, are used in some builds, so you should check if anything you want to build uses them.
I would add some CD4007 devices which can be used for analog switches with no switch pop and some other 15-volt CMOS circuitry to act as silent switch drivers.
Transformers and linear optocouplers are useful for isolating circuitry to avoid ground problems Transformers are also used in some fullwave frequency doublers that give you an output an octave up.
you will never have enough of the right value pots. you need A taper where you want volume/level control. 50kA and 100kA, very common. for oscillators abd some gain control circuits, you want C taper pots. 100kC, 500kC, 1MC. maybe 1kC for your fuzzfaces.
you need sillicon small signal diodes - are they your 1N4xxx? 1N914 or 1N4148 are the GP's. and get some BC548's, just because. also small signal schottkys, BAT something, there's a very popular 1N47something, too. they for reverse protection and your OCD. also 2N7000 and or BS170 [? I think] small mosfets, for all the clean boost. and for your OCD.
and germanium diodes. proper germanium in the big glass case, not dodgy same-numbered sillicon/schottkys small package.
toggle switches, by the thousand, all configurations. cause you'll want them.
and about values - grab a handfull of caps and resistors and throw them on the bench. now make your circuit [breadboard, obviously] using only those parts, see how little the exact value is needed. and welcome.
[edit :] oh, and LM308, LM358, LM741.
Alright, thanks again for all the great information.
Quote from: GibsonGM on November 22, 2022, 01:49:50 PM
and J201 IF you can find them
DigiKey lists the J201, $6 apiece. I understand it's a low noise component, but as it is ten times the price of other similar power handling transistors, I have to ask, is this price rational?
Quote from: duck_arse on November 23, 2022, 09:27:58 AMyou want C taper pots. 100kC, 500kC, 1MC. maybe 1kC for your fuzzfaces.
C-Taper pots: inverse-log? The curve grows fast then flattens rather than growing slowly then spiking, correct?
Quote
and germanium diodes. proper germanium in the big glass case, not dodgy same-numbered sillicon/schottkys small package.
Anyone got part numbers for GE diodes that might exist as new stock at DigiKey (or Mouser)? I can't seem to come up with a search term that doesn't result in Chinesium on Amazon/eBay.
Quote from: amptramp on November 23, 2022, 08:19:03 AM
a photoresistive cell with a few resistors in series and parallel helps make the LED adapt to ambient light
That's a kick-ass idea, thanks! I have a pile of these types of components in my Arduino supplies if I discover a need.
Edit: Fixed formatting
The j201's are really necessary I'm sure someone far more knowledgeable than me can explain why exactly but they just sound better, I've tried to use 5457's in place of them to no real success. These are a good option for them. https://aionfx.com/project/j201-jfet/
Watch out the thru hole version of that part is very commonly counterfeited or I think some places have stock piles of old out of spec left overs they sell.
These are some good germanium diodes
https://stompboxparts.com/germanium/
The 1n34a is kind of the go to, I've bought the 1n34a and 1n276 from here and they spec out just as advertised.
I think some of the parts you'll have a hard time with finding on digikey as they just aren't made anymore.
Since they've become "obsolete" (TO WHOM???), I've made do with others, incl. the 5457, but few subs (that I've tried) will drop right in to an existing circuit.
The J201 is the holy grail of FETs. But due to the 6$ each price, AND huge number of fakes out there, I try to avoid them. MPF102 and others can be played with and adapted to many, many circuits calling for the '201. There's an SMD variety of J201 available, if you like micro work...
I've found a few on Fleabay that were ok, but I hear many are fake.
Quote from: GibsonGM on November 23, 2022, 01:17:29 PMI've found a few on Fleabay that were ok, but I hear many are fake.
I've come to avoid the big marketplaces as I have a tough time differentiating between quality at a good price and overpriced junk. I'm perfectly happy to be limited by my own knowledge and skill, I can learn and practice; Much harder for me to determine that the problem is really a DOA part. I
hope that I can trust suppliers like DigiKey and Mouser that a chip stamped with the TI logo was
actually made by Texas Instruments...
... I think I'm going to need to pare down the order. $400 on silicon to d!ck around with seems a bit excessive ($4000 on siliconE, my opinion might change, hehe). Problem is, everything is cheaper if you buy 10!
Jokes aside, I'm having a tough time finding schematics anywhere on this site, and searching the forums isn't really returning what I'm looking for, have I missed a way of finding this information?
I'm thinking a TS clone of some-sort, I'm not at all fussy, but best I can gather, I'll be able to use a 4558 which I have, and I have enough diodes that I figure I should be able to sit here and try pairs until I like it. This is the first schematic I found that seems reasonable; anyone have a comment or suggestion one way or another?
https://www.diystompboxes.com/smfforum/index.php?topic=77835.0
Thanks!
Welcome to the forum!
Billions of schematics online! Watch out that they're verified good, though. There are some in the forum, and lots in topics (use the search function)
Just a sample of the 'reputable' folks:
https://www.diystompboxes.com/pedals/schematics.html (https://www.diystompboxes.com/pedals/schematics.html)
https://www.electrosmash.com/tube-screamer-analysis (https://www.electrosmash.com/tube-screamer-analysis)
http://www.muzique.com/lab/main.htm (http://www.muzique.com/lab/main.htm)
http://www.geofex.com/schemata.htm (http://www.geofex.com/schemata.htm)
http://www.generalguitargadgets.com/ (http://www.generalguitargadgets.com/)
http://www.runoffgroove.com/ (http://www.runoffgroove.com/)
Quote from: ThePracticalPeasant on November 23, 2022, 01:37:06 PM
I'm thinking a TS clone of some-sort, I'm not at all fussy, but best I can gather, I'll be able to use a 4558 which I have, and I have enough diodes that I figure I should be able to sit here and try pairs until I like it. This is the first schematic I found that seems reasonable; anyone have a comment or suggestion one way or another?
https://www.diystompboxes.com/smfforum/index.php?topic=77835.0
Let's make it more "plain" for the beginning.. :icon_wink:
(https://i.imgur.com/ht5i5DO.gif)
https://www.muzique.com/tech/scream.htm (https://www.muzique.com/tech/scream.htm)
Then you will want to modify it to make it a "Timmy" :)
Never built an effect, get your bread board and start with this.
Note at the bottom of the site is a , in red text "click to download pdf."
https://www.premierguitar.com/diy/pedal-projects/build-your-own-guitar-pedal
Quote from: GibsonGM on November 23, 2022, 03:52:55 PM
Billions of schematics online! Watch out that they're verified good, though. There are some in the forum, and lots in topics (use the search function)
You hit exactly upon my problem - knowing whether what I've found is worth the energy [required to even render the schematic] or not:
I don't know what I don't know! ;)
Quote from: antonis on November 23, 2022, 04:06:56 PM
Let's make it more "plain" for the beginning.. :icon_wink:
I like it. We have a winner.
Quote from: ThePracticalPeasant on November 23, 2022, 09:12:00 PM
Quote from: antonis on November 23, 2022, 04:06:56 PM
Let's make it more "plain" for the beginning.. :icon_wink:
I like it. We have a winner.
Beware of what Sir Mike pointed out.. :icon_wink:
Quote from: GibsonGM on November 23, 2022, 04:39:46 PM
Then you will want to modify it to make it a "Timmy" :)
https://www.diystompboxes.com/smfforum/index.php?topic=121481.0 (https://www.diystompboxes.com/smfforum/index.php?topic=121481.0)
which might result into an addition of a Baxandal EQ plus a phase splitter + octave up plus + plus + plus.. ;)
The TS has a mid hump that's useful for blues tones; but because of this, I find that it doesn't work for 'traditional' hard rock guitar, at least with my rig and a Les Paul. The Timmy does away with this, and the bass and hi cut controls give a lot more versatility, to my way of thinking.
Both have their place (so you'll have to make at least one of each!)
this is your thread now, so if you supply the popcorn, sausages and coffee, you can just scope-out a circuit diagram, post it here and ask questions, compare and contrast. and we'll all pile in and give you helpful hints ......
Get some j113 jfets. Versatile, not expensive and available. I have never understood the J201 hype. Can anyone give me an example of a circuit that will only sound good with a J201 and cannot be adapted for another Jfet? I'd like to listen for myself.
^ That's the one. I'd forgotten that the 113 is a good replacement, thanks for the reminder Clint!
They should make these components in jumbo-sized packages for people with chunky stumpy "mechanic hands" like me...
(https://burningdeep.com/hosted_diystompbox/SOS.1.png)
Used 1N4007s as clipping diodes and RC4558 for the op-amp.
Skipped the volume pot and hardwired to 50% gain for testing.
I spent an hour trying to figure out why it wouldn't work before hooking the guitar to the input and the amp to the output instead of the other way around :icon_rolleyes:
(https://burningdeep.com/hosted_diystompbox/SOS.2.png)
But, it works! Now to learn how/why...
What's that cool looking stringed instrument?
Quote from: Phend on November 25, 2022, 07:07:40 AM
What's that cool looking stringed instrument?
It's one of of a few cigar box guitars built without actual cigar boxes; here's a wider angle.
(http://www.burningdeep.com/hosted_diystompbox/Mini.Guitars.1.png)
I bought, at a junk store, a super cheap cardboard one for super cheap, just to try. I have fun with it but have not plugged it in since I don't trust the super cheap whatever may be inside the thing.
Quote from: ThePracticalPeasant on November 24, 2022, 08:51:42 PM
But, it works! Now to learn how/why...
http://www.geofex.com/circuits/what_are_all_those_parts_for.htm (http://www.geofex.com/circuits/what_are_all_those_parts_for.htm)
http://www.geofex.com/article_folders/tstech/tsxtech.htm (http://www.geofex.com/article_folders/tstech/tsxtech.htm)
Further studying (optional).. :icon_wink:
https://www.tutorialspoint.com/linear_integrated_circuits_applications/linear_integrated_circuits_applications_log_and_anti_log_amplifiers.htm (https://www.tutorialspoint.com/linear_integrated_circuits_applications/linear_integrated_circuits_applications_log_and_anti_log_amplifiers.htm)
(concerning NFB loop clipping diodes..)
Quote from: Phend on November 25, 2022, 10:07:45 AM
I bought, at a junk store, a super cheap cardboard one for super cheap, just to try. I have fun with it but have not plugged it in since I don't trust the super cheap whatever may be inside the thing.
What is there to distrust? Unless there was something wrong with the amplifier that caused a dangerous potential to be put on the input, I can't see how a failure of the electronics in the guitar would be an issue. Am I missing something?
Quote from: antonis on November 25, 2022, 10:28:30 AM
http://www.geofex.com/article_folders/tstech/tsxtech.htm (http://www.geofex.com/article_folders/tstech/tsxtech.htm)
This was great, once I got through a very basic doc on op-amps in general. This is what we've got built, and I've got a couple questions if anyone can help me declutter my understanding. Also a neat project just came about...
(https://burningdeep.com/hosted_diystompbox/SOS.3.png)
1. This configuration is cutting/boosting only the "tone" but generally leaving the signal at the same level? If I were to delete this part of the circuit, I'd only lose the tone control? Do I also need to delete R4? If so, I'm suddenly unsure what C4 is for....
2. Other audio amplifier circuits I've previously worked with had +/- supply rails, I basically understand in this circuit, the waveform's "zero crossing point" is actually at half the amplifier's supply voltage, and this DC must be blocked. I realized after drawing the image...
3. Depending how much of the output gets fed back via the diodes (versus shunted via the pot), we get more/less clipping (from the diodes)? Removing R3/R10 gives a very clean tone. My thought is to put a switch that flips between zero resistance and a 250k pot with a 250k resistor in front of it. This gives a boosted clean and drive tone in the same unit. Thoughts/comments? (the why is coming)
4. Isn't the 4.5V blocked by C2? I don't get what's happening here, but perhaps related to:
5. What's the relationship between the voltage supplied via the 470k here, whatever is happening via C2/R2, and the overall gain of this part of the circuit?
I have a long-standing complaint that drive pedals of all kinds have an output volume shift as the amount of drive is changed. In normal practice it's a non-issue as one could balance the drive and gain pots against the bypassed volume, but this is about to be abnormal.
The first thing I tried once I had a circuit that worked was to put a small speaker across the output and somewhat surprisingly, this circuit was able to drive it directly [albeit very quietly]. This got me wondering:
If I can balance out the "driven" and "clean" tones a bit, and then boost the outputted signal a bit to better drive this little speaker; I have a box of salvaged 18650s to power everything; I think I can build this all into a cigar-box guitar as one self-contained electric instrument.
I actually have amplifier boards based around an LM1875 that I could slap at the end of the whole pedal circuit, but I think that's a bit overkill, power hungry, etc; plus they want a +/- supply. The speaker is only rated 2.5W and fairly responsive; TL022s are rated 680mW; Could I just drive both in parallel?
Whatchall think?
Edit: I said TL022s because I have some, and by both I mean both on the same chip, though the rating might be for the whole package rather than each op-amp. Open to any/all suggestions/ideas!
So I guessed and I'm not sure how I should judge my results. I need a hint.
Fuuuugettabout the active tone circuit, I made this tweak (1k/220 is gain of 4.5, correct?) ...
(http://www.burningdeep.com/hosted_diystompbox/SOS.4.png)
...and it got louder, but has funny behaviour whereby it's only loud when the input is really high, otherwise it's super quiet. Also, more clipping. So I took a guess, the datasheet says in the 100s of nA for the input/bias currents; presumably I need exponentially larger resistors at R5/R6? Also, if whatever was going on wasn't hurting the chip, there might be a "crunch" effect in there somewhere. I'd have to rig an actual guitar through other effects and into more than a little practice amp if I wanted to investigate that further... the Mad Hatter better watch out... ;D
Edit: TLDR: I'm shooting to take the input from a guitar pickup, volume pot for driven tone, volume pot for clean tone, tone pot, microswitch to flip between "channels", running off 12V, outputting half a watt across 6 ohms.
Quote from: ThePracticalPeasant on November 25, 2022, 02:23:34 PM
So I guessed and I'm not sure how I should judge my results. I need a hint.
Fuuuugettabout the active tone circuit, I made this tweak (1k/220 is gain of 4.5, correct?) ...
(http://www.burningdeep.com/hosted_diystompbox/SOS.4.png)
Actually, gain is x5.5 (1+ 1k/220) 'cause it's a non-inverting configuration.. :icon_wink:
BUT
that gain stands for DC also (no cap in series with R6) resulting into op-amp saturation.. :icon_wink:
(output multiplies +4.5V with 5.5 pushing itself up to 24.75V - but it can't go higher than +9V..)
Only negative part of "loud" inputs can be heard (it's subtracted from +9V) and it's "more clipped" due to asymmetrical clipping..
As for previous post questions:
1. R4 & C4 form a Low Pass Filter of -3dB cut-off frequency calculated from : 1/(2πR4C4) where π = 3.14
2. :icon_wink:
3. That's a unity buffer configuration..
4. See my reply on previous post..
(We DO want to block 4.5VDC - here 4.5V point acts as AC ground 'due to C8)
5. No relationship at all..
R1 "brings" +4.5V to non-inveting input and sets particular stage input impedance..
https://www.diystompboxes.com/smfforum/index.php?topic=129863.0 (https://www.diystompboxes.com/smfforum/index.php?topic=129863.0)
(bottom posts)
Quote from: antonis on November 25, 2022, 05:24:34 PM
Actually, gain is x5.5 (1+ 1k/220) 'cause it's a non-inverting configuration.. :icon_wink:
BUT
that gain stands for DC also (no cap in series with R6) resulting into op-amp saturation.. :icon_wink:
(output multiplies +4.5V with 5.5 pushing itself up to 24.75V - but it can't go higher than +9V..)
Only negative part of "loud" inputs can be heard (it's subtracted from +9V) and it's "more clipped" due to asymmetrical clipping..
I suspect the majority of the gaps in my understanding are related to this magical voodoo of mixing AC and DC in the same circuit. I need to remind myself that some components are invisible to certain aspects of the circuit. You've pointed me on a path that I can fiddle with; thanks!
I started the same way...from basic LED circuits, 555 timers and the like. I had to really step back and re-learn a lot to understand that audio signals are AC, a totally different thing. The active things like opamps and transistors run on DC, but they are amplifying AC signals that have been "raised up" (biased) so that they don't cross zero inside the device as they normally would do (DC things can't go below zero, they just cut signals off). Two things going on at once...AC signal, and DC is used to amplify it or filter and so on.
For clarity, AC voltages rise from zero volts to some peak, then come back down and crosses zero, continuing to a negative peak, and repeat...DC is just a straight line voltage that doesn't change. They're both "voltage", but aren't the same.
What happens "inside of the caps" is a mix of AC/DC...the AC rides on a DC BIAS voltage that has been added to it (voltages are perfectly happy to mix together), the component does its amplifying thing, and the output cap blocks DC (strips the DC from the AC), returning the AC in an amplified form. Input caps block the DC operating voltage from getting into things that come before the amplifying device, and also are used to set bass content at the input. Caps "hanging off of" devices are usually filters that send some particular range of frequencies one way or another. So after the initial understanding of how AC goes thru a DC device, you work on how capacitors act like frequency-dependent resistors.
Then all is clear, LOL
I still fudge a lot of fundamentals (I don't like to study the internals of transistors and such), and I've been here for probably 15 years! But I've learned enough by osmosis and reading to help people at times, and to build most any of the stomps you have seen in your wanderings here. If I can do it, you certainly can too! :) Judging by your woodwork, you're the kind of person that will soon eat this up and challenge many of us!
Quote from: GibsonGM on November 25, 2022, 11:32:35 PM
I started the same way...from basic LED circuits, 555 timers and the like. I had to really step back and re-learn a lot to understand that audio signals are AC, a totally different thing.
I remember when I learned how a classic dimmer switch worked. Wait, you mean to tell me that you're using silicon junctions to clip every half wave?! And, a DIAC? How does an AC diode even make sense? ;)
Quote
The active things like opamps and transistors run on DC, but they are amplifying AC signals that have been "raised up" (biased) so that they don't cross zero inside the device as they normally would do (DC things can't go below zero, they just cut signals off). Two things going on at once...AC signal, and DC is used to amplify it or filter and so on.
Is there an advantage with this method versus using +/- supply rails?
Big caps on the output vs the complexities of a dual power supply?
QuoteJudging by your woodwork, you're the kind of person that will soon eat this up and challenge many of us!
I do like to learn, especially the technical details, but I'm flattered, thank you.
Thanks Mike. A lightbulb just went on after all these years :icon_redface:
I come in here several times every day, and I STILL get lightbulbs, LOL! People are so clever that even now, most of these circuits still have things that can be wrung out of them...I really get a kick out of that stuff. Not so into the physics of transistors, however :) I know how they work and how others have set them up to do what they want, good enough for me!
The advantage of using a single supply, of course usually 9V, is the availability, portability and cost of the batteries. And if your intent is to clip a signal and make distortion, you don't need to amplify it to 12 or 18V, only to cut it off at the knees and send it down the line at 1V!! But if you want max clean headroom or to drive a speaker, dual supplies might definitely be the way to go...
Quote from: ThePracticalPeasant on November 26, 2022, 01:39:42 AM
The active things like opamps and transistors run on DC, but they are amplifying AC signals that have been "raised up" (biased) so that they don't cross zero inside the device as they normally would do (DC things can't go below zero, they just cut signals off). Two things going on at once...AC signal, and DC is used to amplify it or filter and so on.
Is there an advantage with this method versus using +/- supply rails?
Big caps on the output vs the complexities of a dual power supply?
Most op amps have a common-mode input voltage range beyond which the circuit may not work properly. If you use ± supplies, you can pretty much be sure you can stay within the usable range with signals that go above and below zero. More importantly, if the plus and minus supplies give you a hard zero as the plus side of the negative supply and the minus side of the positive supply, this is a hard zero point that doesn't move even if a lot of circuit points are connected to it. If you use a single supply and you have a number of connections to the Vcc/2 supply, it is possible for different stages to feed signal back through the Vcc/2 point if it is not decoupled properly. But the use of Vcc/2 gives you an advantage: since your output is referenced to ground, your output coupling capacitor can always have the positive connected to the circuit and the negative going to the output because the output will be referenced to ground. If you have positive and negative supplies, the output will vary above and below zero and you need a non-polarized capacitor to connect the circuit to the output.
I have a fuzz that I have built that uses ±10 to ±15 supplies with internal regulators that give ±5 volts internally. This gives a bit of margin over the 9 volt DC battery supply because I am using TL074 devices and the usable common-mode input voltage range is quite restrictive even though most devices perform better than spec. I use a 10 µF non-polarized electrolytic cap to connect the circuit to the output.
Everything in audio uses ±15V except guitar pedals because 50 years ago something something 9V batteries.
Quote from: ThePracticalPeasant on November 25, 2022, 06:57:25 PM
I suspect the majority of the gaps in my understanding are related to this magical voodoo of mixing AC and DC in the same circuit.
It's called "supeposition theorem".. :icon_wink:
(fancy name but banal application..)
Quote from: GibsonGM on November 26, 2022, 09:06:42 AM
The advantage of using a single supply, of course usually 9V, is the availability, portability and cost of the batteries. And if your intent is to clip a signal and make distortion, you don't need to amplify it to 12 or 18V, only to cut it off at the knees and send it down the line at 1V!! But if you want max clean headroom or to drive a speaker, dual supplies might definitely be the way to go...
I admit that I am combining the two completely unrelated ideas of entering the realm of custom/tweaked/diy FX and self-powering an electric diddley-bow; But when I realized that this tiny overdrive circuit was bordering on powerful enough to drive a small speaker directly, I started to wonder what could be achieved. Being that I can't imagine wanting to play the thing without some amount of overdrive, I thought I might try to explore this avenue, though what ultimately evolves out of this has yet to be seen!
It's complete overkill, but the easiest way for me to get this done would be to use the drive circuit as it is and stick a TDA2050 board after it. As the ones I've got are implemented with big blocking caps for a single power rail, I have a 1A buck regulator I could stick on the 9V to get the 24V the amplifier wants. This setup doesn't give me anywhere near the power for full gain of the chip, but I
would be able to drive this little speaker to its limit.
Slightly off topic but related, I generally have no issue spending good money on parts, components, materials, tools, and supplies that are not only quality but the correct/best for the task. That said, I refuse to throw money away, I detest waste, and insist on getting the most I can out of everything that crosses my path. Following this attitude, I acquired two pairs of these Sony speakers originally part of a reasonable quality CD-changing mini-system (I did make a brief effort to salvage components or otherwise fix the systems, but the amplifier and power supply proved too difficult to separate from the rest of the electronics).
Two of the boards and a 24V 6A supply (would cook these speakers at full gain) is powering the speakers for the TV in my bedroom.
(https://burningdeep.com/hosted_diystompbox/TDA2050.png) (http://burningdeep.com/hosted_diystompbox/TDA2050.png)
The first (somewhat complete) version of the concept, it used (a hugely undersized) external supply so I rigged up the power LED as a (backwards) clip indicator; the system ran the speakers off my desktop computer until I disassembled it for the components.
(https://burningdeep.com/hosted_diystompbox/Amp.Final.Front.png) (http://burningdeep.com/hosted_diystompbox/Amp.Final.Front.png)
(https://burningdeep.com/hosted_diystompbox/Amp.Back.png) (http://burningdeep.com/hosted_diystompbox/Amp.Back.png)
I think I'm in $30? :)
Edit: Formatting/Typo; Reminder to self, ALT+0177;
That's pretty cool. I think many of us have 'hacked' things like that,and come up with some pretty useful things! Repurposing is part of the fun around here.
Quote from: GibsonGM on November 26, 2022, 02:43:45 PM
That's pretty cool. I think many of us have 'hacked' things like that,and come up with some pretty useful things! Repurposing is part of the fun around here.
I got that vibe pretty quick! I've digging around reading old threads and have found some really neat ideas buried in the fora.
Even modifying tape recorders to make tape echoes, LOL
Best way I know to confirm what I've learned and fill in the gaps is to attempt to explain it. If someone would be so kind as to point out my mistakes? I'll end up describing bits of this using the hydraulic analogy for electronic circuits where the energy is shown as balls in the pipe, and where AC currents jiggle in place and and DC currents go around in a loop. When stacked up, it looks like two steps forward followed by one step back. This is the AC riding on the DC. And, for simplicity sake I'll assume that the input to this circuit is a plain old sine wave and we visualize the AC as though the signal jiggles in place. And here's the image again so folks don't need to go scrolling.
(https://burningdeep.com/hosted_diystompbox/SOS.3.png)
1. Presumably the big resistor at R0 is related to noise and/or grounding of the circuit as a whole)
2. Vr is the middle of the signal, we apply a bit of current via R1 to bias C1. The signal now jiggles the cap against the bias, which in turn creates that jiggle at the +input. This is how a passive device is powered.
3. The output is fed back to the -input via D1/D2 (two, one for each direction of the flow, it's still AC after all), which by some kind of magic of their behaviour clip the wave. By forcing more or less of the output back to the -input via the divider created between R3+R10 and R4 the amount of overdrive will change. Again, Vr biases the capacitor C2 so the jiggle is biased by the same amount into both inputs.
4. I presume Ge diodes with their lower forward voltage drop result in inputs to the OpAmp at closer to the same level. I presume various diodes have differing behaviours as they clip. Asymmetrical clipping would be if the diodes behave differently, as the current flowing in each direction would be modified differently. I personally don't know how to distinguish any of these differences, it'll be trial and error for now.
5. (Ignoring the overdrive pot) The divider at R3/R4 is a balancing act. Increasing/decreasing R4 would increase the current at the -input but decrease/increase the level going to the tone circuit respectively.
5a. C1 and C2 need to be as matched as possible;
5b. The size of R2 is related to C2 which in turn is related to the voltage VR
6. The cap at C3 is related to the tone of the drive circuit.
5-6. The output of the Op-Amp is the combination of the input and a bit of the output that has been messed with. It's fairly obvious to me that the output of the Op-Amp becomes the supply rail if these resistors aren't balanced correctly.
==
7. R4/C4 is a low pass filter
8. The wiper position of R11+R4/C5 make a variable low pass filter; When the wiper is at 0, the two inputs of the Op-Amp "have the same tone" as both inputs have the same total capacitors to ground. As the wiper is moved to 20k, C5 is only acting on -input. I presume that R6 limits the effect of C5.
9. The Op-Amp is working off the difference between R11/R5, but one input has been modified by the position of the wiper. The range of R11 and C5 matter as far as the filter is concerned, the size of R11 against R5 matters as far as the Op-amp is concerned. The result of this balancing act is some frequencies being attenuated and some amplified.
==
10. C6 takes the DC bias back out; Too small the AC effectively gets absorbed. Too big and... I have no clue, but I would assume there'd be a reason to keep the size fairly close to minimum required.
Lucky 13: I can confidently say that the variable resistor at the end acts as a volume control by allowing a range from effectively no to full signal through. Other than this, how'd I do?
Here's my working drive circuit that's not adjustable in any way:
(https://burningdeep.com/hosted_diystompbox/SOS.5.png) (http://burningdeep.com/hosted_diystompbox/SOS.5.png)
Edit: Fixed the typos, added added image.
1. No..
It's there to serve as anti-pop (pull-down) item..
(C1 cap leakage might cause popping issues when effect is engaged..)
2. In theory, NO current is applied via R1.. :icon_wink:
(non-inverting input is considered infinite and we DON'T want any DC jiggling there..)
3. Nothing magic there, other than diode(s) shunting signal (of level higher than a diode forward voltage drop) across R10+R3, hence taking it out of the gain loop..
Vr doesn't bias anything here..
(it's used as AV ground point - C2 could equivalently be connected to actual GND..)
4. >I presume Ge diodes with their lower forward voltage drop result in inputs to the OpAmp at closer to the same level<
I'm afraid I can't get you.. :-\
5a. Not at all..
(their values are strongly dependent on R1 and R2 values respectively - both C1/R1 and C2/R2 form HPFs..)
5b. Yes (for C2/R2 relation) and No (for C2/Vr relation)
6. Yes..
It forms a (variable) LPF with R10+R3..
(it actually forms a HPF inside NFB loop, resulting into LPF due to inverted action - just forget it..) :icon_wink:
7. Obviously, yes..
8. http://www.geofex.com/article_folders/tstech/tsxtech.htm][url]http://www.geofex.com/article_folders/tstech/tsxtech.htm (http://[url)[/url]
(https://i.imgur.com/nPg7675.png)
9. See above..
10. C6 isolates (blocks) DC going to output and forms a HPF with Volume pot (in parallel with next stage input impedance)..
I have fundamental gaps in my knowledge and as a result I can only assume that the strange questions I phrase together when I'm only half-way understanding the content are quite hilarious. Thanks for trying to fill in some gaps. I have a couple things on the go, I'll update y'all shortly! :)