I'm just one day into populating two of the Aion Electronics Lab Series boards. It appears D3 and D4, listed as 1N914s in the build doc, may be D4 and D5 on the board. If this is true D3 would be a skipped part#. Can anyone confirm?
That's the way I see it too. The schematic shows D4 and D5 both as 1n4148 which I think are interchangeable with the 1n914 shown in the build doc.
Something else I've noticed:
Both the build doc and schematic shows C51 and C52 as 100uF, but the parts spreadsheet shows these as 220uf. Also the picture of the populated board on Aion's website looks to me like it used the larger 220uf.
I'm inclined to go with the schematics value, but I still consider myself a noob so I thought I'd ask.
I got a real L5 in my studio and I like it a lot for certain things. You wouldn't be able to do a video or just record the sound when they are done?
Now I'm just confusing myself. Don't know where I got 220uF from.
Schematic and parts list show C53-C56 are 270uF.
C51 and C52 are 100uF. I guess I got confused because in the photo they look big for 100uF to me.
Still waiting for a few pots. If I can get this thing working I'll try to make a video report.
Hi, I just build the L5 Preamp and it sounds great, but the popping sound when switching it on or off is horrendous.
Much worse than any of my other pedals.
Anybody else has these problems? Is this normal?
It is not the LED - I disconnected them and it still pops.
It even pops with the Master completely down.
Limiter on or off does not make a difference.
Disconnected D1 and D2 - still popping (what do D1 and D2 do anyway?)
Thank you if you can help
Hi guys! Did either of you get it built successfully? Wondering if someone would be so kind as to compare voltages on two IC's. Specifically IC11 and IC12. The pedal sounds fantastic with an audio probe all the way up to after the Master pot. Electronics are so cooool! Love using an audio probe. haha! Anyway....After that it sounds "garble-y" (....like a distorted vocoder or something haha). Specifically, immediately after R76. Also, the light for the compressor stays on, it gets brighter and reacts to signal when engaged, but when the comp switch is off it stays lit. I tried to be extremely meticulous when installing parts and have since double checked the resistor values in the comp section. I swapped the two CA3080's to see what would happen and the problem persists in the same spot. I also had a RC4558 in IC12 and swapped it for a NE5532 that I had. I double checked pot values, all good. I used !n914's for D4 and D5. All caps were ordered from mouser directly as indicated in the BOM. I just noticed that Kevin has his MPSA13 (Q3) oriented upside down to what is indicated on my PCB.....(i've got mine flat side up) Anyway, here's the IC values both with switch on and off.
I know it's a long shot but maybe someone smarter than me spots something.
Link to schematic...
https://aionelectronics.com/project/lab-series-l5-preamp/
IC11 CA3080 (switch on)
1: 0.000
2: 0.000
3: 0.000
4: -11.04V
5: -10.45V
6: -0.163V
7: +12.90V
8: 0.000
IC11 CA3080 (switch off)
1: 0.000
2: 0.000
3: 0.000
4: -12.03
5: -11.41
6: 0.100 (moving around a lot)
7: +12.91
8: 0.000
IC12 NE5532 (switch on)
1: -0.009
2: -0.001
3: -0.002
4: -11.04
5: 0.000
6: 0.000
7: 0.000
8: +12.89
IC12 NE5532 (switch off)
1: 0.013
2: 0.000
3: 0.000
4: -11.98
5: 0.000
6: 0.000
7: 0.012
8: +12.83
Thanks.
Ryan.
C39 reversed polarity?
Nope. It's installed correctly I think. I checked all the electro caps first thing. In doing so I noticed i did install C40 backwards.... so that was flipped back around. I always forget about tantalums. One day it'll sink in. But that's earlier in the circuit right after the multifilter.
Thanks very much for the response PRR. It does make sense.
Here's a gut shot. Hopefully the embedding works.
(https://www.dropbox.com/s/410z8j32rzajz9i/Photo%202017-01-24%2C%203%2029%2040%20PM.jpg?raw=1)
Kevin says transistor is oriented the correct way. As per pcb.
More data: (compressor on)
-1.4v on cathode side of D4 and D5
Q1 (2n5457)
D: +14.93
S: +0.011
G: -0.139
Q2 (2n3906)
B: -0.647
C: -1.1 shifting
E: 0.000
Q3 (MPSA13)
B: -9.82
C: -6.32
E: -11.32
Immediately before R76 is good, and immediately after R76 is bad?
Any chance for a pic of the other side of the board?
Quote from: EBK on January 26, 2017, 12:47:54 PM
Immediately before R76 is good, and immediately after R76 is bad?
Any chance for a pic of the other side of the board?
Yes that's correct. And on pin 2 of IC12 it sounds okay. Pin 3 is garbled...like DC added sort of. Side question....is leftover flux conductive? Any tips on cleaning it? Makes me nervous scraping it off so I just leave it mostly.
I should clarify, i'm using my iPhone with clean, dynamic, music pumping at roughly 30mV AC for the audio probe. I don't have a scope...yet. Just using the old ears.
Sorry about the massive picture in the last post. Hopefully this will be better.
R76 is just southwest of the inside post of the top right pot. Oriented straight down to the point below.
(https://www.dropbox.com/s/ub1qelptws0l0bc/IMG_5956.JPG?raw=1)
(https://www.dropbox.com/s/2l04u48scjwgxi0/IMG_5959.JPG?raw=1)
I suspect your problem lies around IC11.
Thanks EBK. I'll sniff around...
Quote from: yuka42 on January 26, 2017, 03:13:23 PM
Thanks EBK. I'll sniff around...
Try the easy stuff first: Remove and reinsert IC11. If that doesn't change anything, replace IC11 if you have a spare. If you do not have a spare, try swapping IC10 and IC11.
As a side note, do you have any kind of insulation on the back of that dual pot?
I actually have swapped the two CA3080's with no change. But I have a spare in a compressor pedal i can pop out and swap with just to be sure. Should have bought an extra...
There's three layers of electrical tape on the back of that pot...best i could do in a pinch. But I'll raise it slightly off the board when I test it next. Just to be sure.
Quote from: Rancher on April 25, 2016, 09:16:45 AM
I'm just one day into populating two of the Aion Electronics Lab Series boards. It appears D3 and D4, listed as 1N914s in the build doc, may be D4 and D5 on the board. If this is true D3 would be a skipped part#. Can anyone confirm?
I think D3 is the limiter LED, you're right though, it's omitted. I used 1N4148's for D4 and D5. I ended up using OPA134's in IC1, IC2, and IC13 positions, and TL072 for the rest of the opamps.
Built it recently. It's great! Here's what mine looks like;
(https://aionelectronics.com/wp-content/uploads/2016/11/DSCF5265_1-800x600.jpg)
(https://aionelectronics.com/wp-content/uploads/2016/11/DSCF5266_1-800x600.jpg)
Quote from: stonerbox on May 01, 2016, 03:37:48 PM
I got a real L5 in my studio and I like it a lot for certain things. You wouldn't be able to do a video or just record the sound when they are done?
Here you go...
As for the 2.7uF tantalum cap, you can parallel a 2.2uF with a 0.47uF. That's what I did (look closely at my picture, you'll see the two caps side by side). I got exactly 2.7uF on my cap meter with this combo.
Quote from: yuka42 on January 26, 2017, 03:46:12 PM
I actually have swapped the two CA3080's with no change. But I have a spare in a compressor pedal i can pop out and swap with just to be sure. Should have bought an extra...
There's three layers of electrical tape on the back of that pot...best i could do in a pinch. But I'll raise it slightly off the board when I test it next. Just to be sure.
we can probably assume both chips are good...
Your solder looks good.
Your components appear to be good quality.
Nothing is obviously backward (might consider that tantalum you had temporarily backwards though).
Ive visually double checked about a dozen of your resistor and cap values (assuming they are what they say they are).
Running out of easy stuff to try (which is likely why you are here anyway).
Do you have a spare transistor you could swap in for Q1?
I don't want to risk damaging anything, but if you remove IC11, is the signal good on both sides of R76? (Shooting from the hip with that question. To be more methodical, I would first have to figure out how the circuit is supposed to work. :icon_razz:)
Another check would be to verify all your transistor pinouts, assuming you know the manufacturers. Sometimes they vary.
I'll stop for tonight because I don't think I'm actually saying anything useful. :icon_rolleyes:
Man, I so appreciate the comments. So here's the current situation...
I swapped ic11 with the one I had in the comp pedal. Still no good which I kinda figured. I looked at the mpsa13 values and they kinda gave me a weird vibe. Hahaha. I looked up voltage drop and it seemed too much? I honestly need to go to school for this stuff. Anyway, I swapped it with a spare I had and the garble disappeared!! Woooo! That'll teach me to socket transistors. But.... comp circuit still is weird. I'll recalibrate it tomorrow. But the light remains on in either switch position and it doesn't seem to be dancing or making a dif on volume levels anymore. Maybe someone can comment on exactly how their comp circuit responds? Is the level control a threshold? Or input volume...
Here's the new darlington values. (Mpsa13)
C: -10.38. (Was -6.32)
B: -9.78
E: -11.04
Done for the night. Thanks again.
The limiter control is counter-intuitive. Think of it as a sensitivity control, but backwards. It's most sensitive at 0, and least sensitive at 10. If you're going to use it, start at 10 and dial down until you get the desired limiter engagement. It also depends where you set your preamp volume as well. If your channel volume is at 0, and your limiter is at 10, and the LED is still lit, there's a problem.
Excellent. Thanks for the explanation. That'll help out diagnosing...
Should I be seeing DC after C38? What would the purpose of the diodes be after C38? D1 and D2.
Quote from: yuka42 on January 29, 2017, 07:12:40 PM
Should I be seeing DC after C38? What would the purpose of the diodes be after C38? D1 and D2.
I suspect those diodes are there to protect pin 3 of IC12, but they are drawn in an odd place on the schematic....
What level of DC are we talking about?
Are you seeing the same level before C38?
I believe you should see no DC. Everything appears to be ground referenced with no other DC source in sight, unless you have D1 or D2 backwards.
A loudspeaker cable will fit the Output jack. 30V of speaker AC _IN_to the output will blow things up.
The 2K and diodes to rails limit the damage.
C38 may leak a small current. With COMP switch OFF, there is no in-box bleeder path, so there may be some DC voltage. Switching Comp to ON will bleed this. Hanging say 100K at the D1 D2 junction to ground will bleed this.
okay. Thanks again for the lessons. It was in the millivolts after C38 which eventually, on second inspection, drained to naught. Just kinda grasping at straws is all. I've since found that the garble did not go away but in my fiddling, the comp section was shorted to ground. Fixed the bridge and now back to square one. I have reheated as much of the comp section solder points as I can and examined this thing with a fine tooth comb for solder bridges etc. My only other remaining thought is perhaps something is bridging in the IC sockets themselves which seems unlikely and a massive pain to remove. I have discovered (perhaps) some more clues but have been researching things to try to wrap my brain around the circuit a bit. Reading on the CA3080 and it's operation etc (which is, I'll admit, a bit above my pay grade).
Here's a fantastic write up...for someone smarter than I.
http://www.diystompboxes.com/smfforum/index.php?topic=63724.0 (http://www.diystompboxes.com/smfforum/index.php?topic=63724.0)
-I've socketed all 3 transistors and when Q2 (2N3906) is removed, the audio clears up and sounds great (and obviously the comp section stops working).
-with Q2 removed, the audio is clear all the way up to the cathodes of D4 and D5. On the anodes it sounds crackly, which worsens when the comp level is adjusted to the louder.
-I'm using Tayda's version of the 1N914 for those...which look different than Aion's and digi2t's.
-with Q2 and Q3 Installed and the 3080 removed i see -7.14V on the socket pin 5.
-seeing how pin 5 on the CA3080 is the bias input....does it make sense that I would see -12.28V on that pin with both Q2 and Q3 removed and the IC is installed? I would assume it would be 0V since it's an input. (I'm thinking very linear-ly.) Or have I blown pin 5?
The way I'm envisioning (read guessing) this thing working, is that when the comp is OFF, the CA3080 works as a normal opamp with a FET after it's output. When the comp is ON, the audio goes through IC12 and is rectified and amplified through the diodes and Q2, then transmitted to the bias input on pin 5 of the 3080. Thereby forcing it to react to the bias and change it's output level (e.g. compress)? I'm not exactly understanding the purpose of the darlington, other than as a part of the LED circuit. I'm probably way out to lunch, but I do love a good sandwich. :icon_wink:
http://www.diystompboxes.com/smfforum/index.php?topic=113344.msg1049106#msg1049106 (http://www.diystompboxes.com/smfforum/index.php?topic=113344.msg1049106#msg1049106)
Essentially the same circuit in the design stage with Aion. I learned a bit from it though so thanks PRR! :icon_biggrin:
Hi all!
I just started this build and I am on the "parts hunt phase".
I was wondering if anyone that has the pedal working could measure the amp drainage of it. I am looking for a couple of AC/AC adapters and I am not sure what is the minimum miliamps that it needs to provide.
Thanks!!!
Quote from: bsas on February 04, 2017, 12:24:22 PM
Hi all!
I just started this build and I am on the "parts hunt phase".
I was wondering if anyone that has the pedal working could measure the amp drainage of it. I am looking for a couple of AC/AC adapters and I am not sure what is the minimum miliamps that it needs to provide.
Thanks!!!
There's a link in the build doc that points towards suitable power supplies. For what they cost, I always go bigger when it comes to power supplies. A 1000mA adapter doesn't cost much more than a 500mA or 750mA. For 2 or 3 dollars more, I say go for it.
The thing is that I found a 400mA adapter that is very small and white.
I like that it is white because then I will not mix with my DC adapter and burn my other pedals. And I like the size because of portability. I just want to know if 400mA is enough, I am not worried about price (specially on this build).
Ah! Also I was suffering to find a 2.5kA pot (i even asked you on youtube :D), but I have an idea that I would like to share and ask if it is crazy:
If I get a 5kA dual pot (which is very easy to find on Tayda) and I join each top lead to the bottom one, I think it will behave like a 2.5kA because 2xR parallel resistors should give me R/2 resistance (so 2x5k = 2.5k), and being log taper (both tracks) I think it should give me a similar taper behavior (that is the part I am not sure).
Am I tripping or does that make sense? Thanks!!!
Quote from: bsas on February 05, 2017, 11:12:04 AM
Ah! Also I was suffering to find a 2.5kA pot (i even asked you on youtube :D), but I have an idea that I would like to share and ask if it is crazy:
If I get a 5kA dual pot (which is very easy to find on Tayda) and I join each top lead to the bottom one, I think it will behave like a 2.5kA because 2xR parallel resistors should give me R/2 resistance (so 2x5k = 2.5k), and being log taper (both tracks) I think it should give me a similar taper behavior (that is the part I am not sure).
Am I tripping or does that make sense? Thanks!!!
I've done that trick before. It works fine.
Build report: main parts soldered! :D Please let me know if you guys spot any obvious problems.
Waiting for big parts to arrive, like pots, 3PDT and enclosure.
(https://content-na.drive.amazonaws.com/cdproxy/templink/zsgA2nNalML1IJXJcH09SQmnO_qWKU4fZ-lhEhwYefIeJxFPc/alt/thumb?viewBox=1920)
(https://content-na.drive.amazonaws.com/cdproxy/templink/hWohUqf4Ush1K8-k2nL8H9b4dPVzmPNUW2SWBuGcaeQeJxFPc/alt/thumb?viewBox=1920)
P.S.: Love when the solder points look like Hershey kisses :D
Quote from: yuka42 on January 30, 2017, 08:35:51 PM
-I've socketed all 3 transistors and when Q2 (2N3906) is removed, the audio clears up and sounds great (and obviously the comp section stops working).
-with Q2 removed, the audio is clear all the way up to the cathodes of D4 and D5. On the anodes it sounds crackly, which worsens when the comp level is adjusted to the louder.
Sounds like your problem is round this area, you shouldn't really hear any audio on the anodes of d4 and d5, C39 should be smoothing the signal into a DC voltage. If you're getting audio there that would explain why it sounds garbled. I would try replacing C39 and making sure you have continuity between the positive end of C39 and the diodes and from the negative end and -V, also check the value and connections to R94
Thanks for reply Slacker!! You inspired me to take another peek at the pedal today. I decided to replace the Tayda 1n914 diodes with a pair I got from mouser which match every other Lab build has that I've seen. And what do ya know......the garble stopped. Comp working as it should. No more DC on the output. LED is lighting as it should. After all that routing around it must've been those diodes. As much of a headache it was to sort that problem out I sure learned a lot about the circuit and the CA3080 in the process. I walk away a smarter man. Haha. And I've got a wicked pedal. So thanks everyone for the inspiration and helping hand.
Kudo's to Kevin at Aion. Must've been some amount of work to put this into pedal form. It sounds great. The sweepable mid frequency is the most useful thing to have in a recording studio pedal board and it sounds fantastic. Very excited to put this thing through its paces.
Ryan
Hi all!
So, my turn of having weird issues with the build :(
1) Children boards LEDs behavior:
First I tried to wire the LEDs in the standard "on/off" mode where you "link" both small boards by the "CH" lug. The LEDs never turned off. The weird thing is that both 3PDT were working fine and doing what there were suppose to do but the bypass LED and the channels LED were always on.
Then I removed the link and I wired the CH from the channel select board directly to ground (the "always on channel LEDs option) and all LEDs work fine now, with a small exception that the bypass LED is never fully "off". It is like very weak light while off and very strong while on.
2) Compressor muting the note attack instead of compressing:
The pedal sound OK, I guess, and everything looks like it is working but the compressor is very weird. Basically I can see it acting and it's LED blinks when it grabs a high peak note as expected, but sound wise, instead of compressing the signal, it mutes the attack of the note and the volume comes back slowly. It almost sounds like a buggy noise gate.
3) Low output:
Being a preamp pedal I was expecting a monster amplification, but, for me I need to put volume at 12 and master almost at 12 to be kind of unity level. Am I missing something here?
4) A lot of heat from voltage regulators:
The voltage regulators run quite hot all the time. I already measured the +|- 15V pins and they measured perfectly. Is that expected?
Thanks all!!! :)
Interesting findings:
I can measure voltage on the Q3(MPSA13) pins, but, if I remove it, the sound of the compression stays the same (AKA bad). Seems to me that somehow it is getting ignored. I already tried to replace the MPSA13 with a couple others and it doesn't help.
Also, when I turn the unit ON the compressor LED lights up and fades out slowly...
Hey all,
I just finished this build. Everything works and sounds pretty good, but I'm having difficulty calibrating the distortion trimpot. I have a 1kHz sine wave measuring 30mV with my cheapo Radio Shack DMM:
(http://i64.tinypic.com/2vsnf2q.jpg)
However, when I apply the signal to pin 2 of IC10 (CA3080), I don't get anywhere near the 4.4V AC required by the spec at pin 6. I'm getting readings in the millivolt range no matter where I set the trimpot.
(http://i63.tinypic.com/2gue8fk.jpg)
Am I doing something incorrect or is there a problem with my IC? As you can see from the pic, I'm applying the signal directly to pin 2 and measuring at pin 6 rather than using the test pads (I forgot to solder pins to the test pads and now can't reach them easily). My black test lead on my DMM is connected to the common ground at the input jack. I have the pedal powered on with a Line6 Px-2g 9VAC power supply. The V+ and V- on the pedal are right around 15 volts, as they should be, including as measured on pins 4 and 7.
Any help would be most appreciated!
Thanks,
Jason
Was the headphone volume set all the way up before you dialed in the 30mV?
Maybe the compressor is interfering? Adjust the compressor trimmer and see if it affects the distortion voltage. If so, adjust it to the end, so as it raises the distortion voltage. Then go back to the distortion trimmer. Then set the compressor.
I'm just spitballing here.
Quote from: digi2t on February 16, 2017, 09:12:11 PM
Was the headphone volume set all the way up before you dialed in the 30mV?
Maybe the compressor is interfering? Adjust the compressor trimmer and see if it affects the distortion voltage. If so, adjust it to the end, so as it raises the distortion voltage. Then go back to the distortion trimmer. Then set the compressor.
I'm just spitballing here.
Yes, the headphone volume was up all the way. I'll try the compressor trimmer. Thanks.
Turn the compressor switch off, so it will remove it from the circus and will isolate the distortion circuit :)
Quote from: bsas on February 16, 2017, 10:30:44 PM
Turn the compressor switch off, so it will remove it from the circus and will isolate the distortion circuit :)
Thanks, but I've tried it with the compressor switch both off and on and it makes no difference either way. The range I'm reading on pin 6 of IC10 is ~58mV with the trimpot all the way counterclockwise and ~16mV with the trimpot full clockwise. Changing the trim value does have an audible effect on the Master Volume level, so I know it's doing something.
I noticed something interesting: If I apply 1kHz 50mV sine wave on the circuit input, with my current configurations, I can measure 450mV across C38 if the compressor switch is OFF. If I turn the compressor switch ON and set the LIMIT where it can kick in constantly, the voltage across C38 drops to 17mV!!!
Bumping this up. I tried swapping the two CA3080s on the board and got the same results, so it looks like my problem is not with the ICs themselves. Does anyone how has also built this project have any ideas about what might be happening? Much appreciated in advance!
Bumping this up also because I already lost my hope to find the compressor issue by myself :(
I will basically forget about the pedal waiting for a good soul to give me any tip about what should I debug...
Quote from: jstone on February 17, 2017, 09:36:14 PM
Bumping this up. I tried swapping the two CA3080s on the board and got the same results, so it looks like my problem is not with the ICs themselves. Does anyone how has also built this project have any ideas about what might be happening? Much appreciated in advance!
I apologize if this has been mentioned already in the thread, but where did you source your 3080's (all your parts for that matter) from? If the y came from a dealer of ill repute, and are both fakes, then it wouldn't really matter which chip you put in which slot, now would it?
Also, go over all your resistors again. Ensure that you don't have a 220R in place where a 220K should be, or something like that. We had a forumite, paulyy, here a while back. He was building the Colorsound Vocalizer, and after several days of wits end drama, he still couldn't get it to work. I finally offered to look at it, so he sent it to me. First thing I did was go over all the components with a fine toothed comb. I found one resistor, if memory serves me, a 22K where a 2.2K should have been. The difference between the red and orange on the third band was so subtle, anyone could have mistaken it for one or the other value. It's for this reason that my meter is always on when I'm loading resistors, and each one gets checked before I load it onto the board. Yes... even if the package is properly labelled, and I've just pulled 3 good ones out of it. I myself got played with this when I first started building, due to incorrect package labelling. The resistor pack was labelled as one range, when in fact it was another. Trust me, when you pull out enough hair, you don't want to go through that twice. I don't care if I've pulled 45 resistors out of a pack, and every one has been the right value as per the package label, I'll still pass them though the DMM. 3 seconds spent here, is hours of troubleshooting saved later.
As for this project, mine fired right up, and the tuning was as per the instructions. The only changes I made were IC types, settling on OPA134's in IC1, IC2, and IC13 positions, and TL072 for the rest of the opamps. But really, it worked fine right out of the gate with the originally spec'd IC's, so I don't see this as a problem. The IC swaps were to please my own ears.
Thanks digi2t. I bought my parts from Mouser and Small Bear. The 3080s came from Small Bear and I've actually ordered four more just to be sure. They should arrive today. I also ordered more trimpots from Mouser.
I'm going to go over all the resistors as you suggest and will report back.
Quote from: jstone on February 18, 2017, 09:42:55 AM
Thanks digi2t. I bought my parts from Mouser and Small Bear. The 3080s came from Small Bear and I've actually ordered four more just to be sure. They should arrive today. I also ordered more trimpots from Mouser.
I'm going to go over all the resistors as you suggest and will report back.
OK. Good sources on both fronts.
Don't be afraid to take a break from it as well. Sometimes, the harder you stare at something, the less you see. I find that sometimes taking a break from the problem, and doing something completely different, helps reset the brain. Take a few days off, and come back to it fresh. You might be surprised at how quickly the problem might reveal itself, and you'll wonder how you never saw it the first time around. (DOAH!! ;))
I went back and checked all the resistor values. Wow! I counted nearly two dozen resistors that are significantly off-spec. R2 is supposed to be a 1M resistor, but I measure it at 220K! I guess I need to order some replacements. From now on I will measure everything before soldering.
Quote1) Children boards LEDs behavior:
First I tried to wire the LEDs in the standard "on/off" mode where you "link" both small boards by the "CH" lug. The LEDs never turned off. The weird thing is that both 3PDT were working fine and doing what there were suppose to do but the bypass LED and the channels LED were always on.
Then I removed the link and I wired the CH from the channel select board directly to ground (the "always on channel LEDs option) and all LEDs work fine now, with a small exception that the bypass LED is never fully "off". It is like very weak light while off and very strong while on.
I had the very same issue. Could only get it to work in the "channel always on" configuration by grounding in to the board. I don't have the low light bypass issue though....the bypass shuts off. I like that it shows the channel when bypassed anyway.
If you need to compare voltages I'd be happy to now that mine's up and running. It has PLENTY of gain. My Master pot hasn't exceeded noon....
I calibrated the comp trim pot sort of in-between the recommended voltage and all the way off (as kevin states in his build doc....he left it at zero to get more useable control).
My voltage regulators get quite warm as well.....
I'll have more time to help tomorrow.
As a side note, I downloaded the build doc when he first posted it, which originally had C51 and C52 at 100uf. They are now 270uf. I installed the 270uf.
QuoteI went back and checked all the resistor values. Wow! I counted nearly two dozen resistors that are significantly off-spec. R2 is supposed to be a 1M resistor, but I measure it at 220K! I guess I need to order some replacements. From now on I will measure everything before soldering.
The measurements of resistor values will not be to spec when installed in a circuit. It will take into account the surrounding components in the circuit. I would download a resister colour code app and use that.
Quote from: yuka42 on February 18, 2017, 01:50:04 PM
QuoteI went back and checked all the resistor values. Wow! I counted nearly two dozen resistors that are significantly off-spec. R2 is supposed to be a 1M resistor, but I measure it at 220K! I guess I need to order some replacements. From now on I will measure everything before soldering.
The measurements of resistor values will not be to spec when installed in a circuit. It will take into account the surrounding components in the circuit. I would download a resister colour code app and use that.
+1. Measuring resistors on the board will not give you accurate measurement. Like yuka says, you're probably reading other resistances in parallel or series with the component you're reading. Get the color chart out, and a good magnifying glass.
Quote from: digi2t on February 18, 2017, 04:00:24 PM
+1. Measuring resistors on the board will not give you accurate measurement. Like yuka says, you're probably reading other resistances in parallel or series with the component you're reading. Get the color chart out, and a good magnifying glass.
Good points, thanks. I'm still new to this, but I figured if I just measured from one resistor lead to the other, I would be measuring just the resistance of that single component. I see it doesn't work that way once everything is hooked up.
Quote from: yuka42 on February 18, 2017, 01:39:04 PM
If you need to compare voltages I'd be happy to now that mine's up and running. It has PLENTY of gain. My Master pot hasn't exceeded noon....
Hi yuka42, thank you for helping me! :D
Here is my detailed and boring voltages:
1) Knobs for ALL measurements:
- All knobs are at noon, except both Volumes which are MAX, Master is MAX, and Limit is around 2:00 (according to calibration instructions);
- Bright switches OFF, Input at HI
2) What I did to calibrate:
Following instructions AS IS, I pumped 1kHZ 30mVA on IC10:PIN2 and I was able to calibrate:
- IC10:PIN6: 4.41 VA (4.337 VA with Comp ON)
- PIN_OUT to 1.171 VA with Comp ON
3) I already measured the D4 and D5 diodes (from Mouser) and they both check -0.6V drop.
4) The Comp LED blinks on the expected moments, when I make a hard attack on my notes, and it fades out as expected too, while the note fades out. The problem is the sound. I am expecting my note to squick (compress) but instead if literally mutes the note completely on the attack and if "fades in" if I let the note ring. Almost sounds like if the moment the Comp LED blinks, my guitar volume drops to zero, and then slowly comes back like I am sweeping the volume knob back to 10 (tricky to explain).
5) Measurements:
- All are made with 4 possible scenarios:
A - 1kHZ 30 mVA on IC10:PIN2 / Comp ON (this is where the problem happens, and the Comp LED is always ON).
B - 1kHz 30 mVA on IC10:PIN2 / Comp OFF
C - 0 mVA on IC10:PIN2 / Comp ON
D - 0 mVA on IC10:PIN2 / Comp OFF
- If I use (...) I mean voltage AC, If I don't, means DC:
IC10:
| A | B | C | D |
1 | (0.09) | (0.09) | (0.152) | (0.152) |
2 | (0.03) | (0.03) | (0) | (0) |
3 | 0 | 0 | 0 | 0 |
4 | -15 | -15 | -15 | -15 |
5 | -14.32 | -14.32 | -14.32 | -14.32 |
6 | (4.33) | (4.41) | (0) | (0) |
7 | 14.96 | 14.96 | 14.96 | 14.95 |
8 | (0.130) | (0.130) | (0.130) | (0.130) |
IC9:
| A | B | C | D |
1 | (0.23) | (0.69) | (0) | (0) |
2 | 0 | 0 | 0 | 0 |
3 | 0 | 0 | 0 | 0 |
4 | -15 | -15 | -15 | -15 |
5 | 0 | 0 | 0 | 0 |
6 | 0 | 0 | 0 | 0 |
7 | 0 | 0 | 0 | 0 |
8 | 14.96 | 14.96 | 14.96 | 14.96 |
IC11:
| A | B | C | D |
1 | (0.117) | (0.117) | (0.117) | (0.117) |
2 | (0.22) | (0.05) | (0) | (0) |
3 | 0 | 0 | 0 | 0 |
4 | -15 | -15 | -15 | -15 |
5 | -14.32 | -14.32 | -14.32 | -14.32 |
6 | (1.25) | (3.9) | (0) | (0) |
7 | 14.96 | 14.96 | 14.96 | 14.95 |
8 | (0.130) | (0.130) | (0.130) | (0.130) |
IC12:
| A | B | C | D |
1 | (0.74) | (0) | (0) | (0) |
2 | (0.067) | (0) | (0) | (0) |
3 | (0.067) | (0) | (0) | (0) |
4 | -15 | -15 | -15 | -15 |
5 | 0 | 0 | 0 | 0 |
6 | 0 | 0 | 0 | 0 |
7 | (0.74) | (0) | (0) | (0) |
8 | 14.96 | 14.96 | 14.96 | 14.96 |
Q1 - 2N5457 (this guy I wasn't sure to measure AC or DC, so I did both):
| A | B | C | D |
D | 0 | 0 | 0 | 0 |
S | (1.17) / -0.17 | (3.7) / -3.9 | (0) / -0.42 | (0) / -0.42 |
G | (1.27) / 0.32 | (4.1) / -3.4 | (0) / 0.03 | (0) / 0.03 |
Q2 - 2N3906:
| A | B | C | D |
C | 0 | 0 | 0 | 0 |
B | -0.58 | 0 | 0 | 0 |
E | -12.3 | -14.4 | -14.4 | -14.4 |
Q3 - MPSA13:
| A | B | C | D |
E | -15 | -15 | -15 | -15 |
B | -13.76 | -14.3 | -14.3 | -14.3 |
C | -14.32 | -0.385 | -0.385 | -0.385 |
Quote from: yuka42 on February 18, 2017, 01:39:04 PM
My voltage regulators get quite warm as well.....
I measure 100F - 120F :O. I hope that is expected...
QuoteThe Comp LED blinks on the expected moments, when I make a hard attack on my notes, and it fades out as expected too, while the note fades out. The problem is the sound. I am expecting my note to squick (compress) but instead if literally mutes the note completely on the attack and if "fades in" if I let the note ring. Almost sounds like if the moment the Comp LED blinks, my guitar volume drops to zero, and then slowly comes back like I am sweeping the volume knob back to 10 (tricky to explain).
You mean like a limiter. Description;
A limiter is a device designed specifically to prevent audio levels from going higher than a specified point. In practice a limiter is basically a compressor with a very high compression ratio (20:1 to infiniti:1). The idea is that once the level reaches a certain point, the limiter will not let it go beyond that. In practice, that's what this compressor does. The lower you set the pot (counter clockwise), the more it will clamp down on louder signals. When I do use it, I set it right on the edge of my hardest attack, and then a tiny bit more. It doesn't mute my hard attacks, but it does keep them from spiking the rest of the passage.
Quote from: jstone on February 18, 2017, 04:34:11 PM
Quote from: digi2t on February 18, 2017, 04:00:24 PM
+1. Measuring resistors on the board will not give you accurate measurement. Like yuka says, you're probably reading other resistances in parallel or series with the component you're reading. Get the color chart out, and a good magnifying glass.
Good points, thanks. I'm still new to this, but I figured if I just measured from one resistor lead to the other, I would be measuring just the resistance of that single component. I see it doesn't work that way once everything is hooked up.
I went back through and checked the color codes of all the resistors I thought were not measuring correctly, and the color codes are all correct. Back to square one. Any other suggestions before I pull the board out and check for solder issues? As I mentioned in an earlier post, the pedal seems to be working, although I'm clearly not getting the correct voltages out of IC10.
Quote from: jstone on February 18, 2017, 11:23:29 PM
Quote from: jstone on February 18, 2017, 04:34:11 PM
Quote from: digi2t on February 18, 2017, 04:00:24 PM
+1. Measuring resistors on the board will not give you accurate measurement. Like yuka says, you're probably reading other resistances in parallel or series with the component you're reading. Get the color chart out, and a good magnifying glass.
Good points, thanks. I'm still new to this, but I figured if I just measured from one resistor lead to the other, I would be measuring just the resistance of that single component. I see it doesn't work that way once everything is hooked up.
I went back through and checked the color codes of all the resistors I thought were not measuring correctly, and the color codes are all correct. Back to square one. Any other suggestions before I pull the board out and check for solder issues? As I mentioned in an earlier post, the pedal seems to be working, although I'm clearly not getting the correct voltages out of IC10.
Did you tried to put all knobs at noon? I notice that when some knobs are too high or too low, the IC10:6 never reaches 4.4V in my case. I made sure that all knobs where noon except all volumes and master, which were MAX.
Quote from: digi2t on February 18, 2017, 10:45:13 PM
QuoteThe Comp LED blinks on the expected moments, when I make a hard attack on my notes, and it fades out as expected too, while the note fades out. The problem is the sound. I am expecting my note to squick (compress) but instead if literally mutes the note completely on the attack and if "fades in" if I let the note ring. Almost sounds like if the moment the Comp LED blinks, my guitar volume drops to zero, and then slowly comes back like I am sweeping the volume knob back to 10 (tricky to explain).
You mean like a limiter. Description;
A limiter is a device designed specifically to prevent audio levels from going higher than a specified point. In practice a limiter is basically a compressor with a very high compression ratio (20:1 to infiniti:1). The idea is that once the level reaches a certain point, the limiter will not let it go beyond that.
In practice, that's what this compressor does. The lower you set the pot (counter clockwise), the more it will clamp down on louder signals. When I do use it, I set it right on the edge of my hardest attack, and then a tiny bit more. It doesn't mute my hard attacks, but it does keep them from spiking the rest of the passage.
Well, I know what a limiter should do :D I already built a couple.
Unless the limiter circuit in this pedal is the most weird I ever heard (and unfortunately I never heard the original amp to compare), I strongly think something is wrong, because if I for example play the note to the edge of the limiter to kick in, the note drops to zero, believe me. I can record if you guys want.
It is like this:
Uncompressed sound wave:
/\ /\ /\
/ \ / \ / \
------------------------
\ / \ / \
\/ \/ \
Expected limiter result:
__ __ __
/ \ / \ / \
------------------------
\ / \ / \
-- -- -
What I am getting:
_ /\ /
/ | /\ /\ / \ /
------------------------------------------
(1) (2) \/ (3) \/ \ /
\/
(1) = sudden drop and big silence
(2) = note fades in slowly
(3) = eventually comes back partially full (if it is not on the limiter threshold)
Like I said, almost sounds like if I move the volume of my guitar to 0 the moment the limiter grabs the attack, and I slowly fade-in back from 0-10 in a matter of some seconds (between 1-2 seconds).
You can actually hear a "POP" the moment the circuit grabs the attack, almost like if I step in the 3PDT bypass switch.
It is weird! :D
Your "expected limiter result" is incorrect.
Basically, it is not a "hard clipping", not even "soft clipping", -type limiter, so there isn't supposed to be distortion at waveform peaks, instead transients and notes with high enough amplitude and sustained envelope should gradually decrease signal gain in order to prevent clipping in stages that follow. Refer to graph titled "limiter with moderate attack and release" for example. It is common that fast attack characteristics may introduce some waveform distortion for very brief moments, like in the graph above but basically the operation of the limiter should be "inaudible" distortion wise.
(http://ffden-2.phys.uaf.edu/211_fall2013.web.dir/Jay_Byam/Jay_Byam/Images/compression.png)
So if the compressor entirely mutes your signal, pretty much immediately on note attack, and then gradually starts to recover gain when note's amplitude fades it is a sign of the compressor acting oversensitively, or at least introducing way too much attenuation: Instead of -proper amount- of attenuation during attack it entirely mutes your signal. ...and keeps it muted for a long time until below compressor's threshold the gain starts to eventually recover.
Yes, it is common to hear "POP" sound when signal rapidly goes muted. It's the sound of waveform distortion and "edge" in the waveform at the point where it quickly dives from some arbitrary voltage level to zero volts (muted).
The compressor circuit itself is very simplistic: You have feedback loop around JFET gain stage and an operational transconductance amp in that loop. Gain of the aforementioned amp can be controlled with its Iabc input (Pin #5) and since the stage is -inverting- its output signal is subtracted from (input) signal at JFET's gate, which in turn means attenuation of signal. With no output from OTA there is no attenuation (no subtraction) and with OTA output equal to input signal's amplitude you get full attenuation and the signal is effectively muted. These are the circuit elements that actually control gain, everything else is for controlling those elements and establishing the proper operating point.
The input to compressor circuit is a basic passive attenuator consisting of potentiometer and trimmer for fine tuning. Following the attenuator is a gain stage with gain of around 11x and a full wave rectifier consisting of pair of diodes and an inverting unity gain amplifier. Full wave rectified (and filtered) signal controls transistor Q102's base, and that transistor controls Iabc input of the OTA and drives another transistor, which just drives that LED indicator. R183 controls Iabc current and basically sets the operation point of the OTA to match voltage levels of the circuit. Too much current and the OTA is toast, too little and it will not attenuate.
This is a very simple and extremely basic compressor circuit since its attack and decay characteristics are entirely controlled by that single filter cap C139 and associated RC time constants. Not "high fidelity" even by a longshot but likely sufficient enough for a guitar amp.
(http://i1249.photobucket.com/albums/hh506/aionelec/comp.jpg)
So, I would check that the trimmer is adjusted correctly (as per instructions in the schematics) and that all component values are correct. OTA, for example, does not accept high amplitude input signals so make sure it actually has that huge amount of attenuation in its inverting input. Do note that in comparison to generic opamp gain stages this one is -open loop- and has tons of voltage gain. You only need few millivolts of signal to generate an output signal with magnitude of couple of volts. Proper input attenuation is therefore extremely important! Also make sure that you got that current limiting resistor in Iabc input right.
Wow!!! Thank you so much for this very detailed explanation teemuk!
You just made me understand at least 5X more of how this circuit supposed to work :)
Well, I have setup the trim pot according to the schematic (1.17V with the pot set to 2:00). I will double check again the things you pointed out and try to find where the Iabc got so much cancellation.
Thanks!!!
teemuk, I love you :)
My circuit was correct all along! I was just miss adjusting and miss using it!
After your explanation I was able to measure it with my oscilloscope and properly adjust the trim pots, and now everything sounds great!
My main issue was that I was trying to use the limiter with the "Limit" knob almost all down, around 9:00. This is why the volume drop was so drastic. After your excellent explanation I checked online a picture of the original amp limiter knob, and I finally understood it properly.
Now setting it to "0", or around 2:00, sounds awesome!
Thank you all!!! :)
Ha!! What an explaination!! Fantastic. Glad you got it sorted. Have fun!
I've been thinking a little more about my issue - too low voltage output on pin 6 of IC10. I checked the values of the trimpot (20k) and all of the nearby components on the schematic. Everything seems to check out. I'm getting the correct V+ and V- measurements on pins 7 and 4. So I should be getting somewhere close to the right output out of pin 6, no? If this is the right analysis, can I conclude that I have a bad IC?
The first thing I always do is replace critical ICs just to be sure. Doesn't hurt to try :)
I would put a known sine wave in the input of the pedal and measure all opamps and OTAs in and outs too check if something is odd...
Quote from: bsas on February 20, 2017, 12:17:44 AM
The first thing I always do is replace critical ICs just to be sure. Doesn't hurt to try :)
I would put a known sine wave in the input of the pedal and measure all opamps and OTAs in and outs too check if something is odd...
Do you mean just take a 1/4 cable and plug it straight into the input of the pedal with a sine wave on it?
Quote from: jstone on February 20, 2017, 11:45:26 AM
Do you mean just take a 1/4 cable and plug it straight into the input of the pedal with a sine wave on it?
Yep! With a multimeter you can check if the sound wave is going over the spots. And if you want to be fancy, you can use an audio probe too :)
+1 for the audio probe. Here's a good link.
http://www.diystompboxes.com/pedals/debug.html
It's a great learning tool. Follow the circuit with it and hear what components are doing. Invaluable.
Hi everyone,
I'm embarrassed to say that I think the reason I was not measuring the right voltages on IC10 is because I'm a n00b and just wasn't measuring it correctly. When I applied the sine wave to pin 2, I was just using a lead from the tip of my headphone cable and I had disconnected the ground connection from the sleeve. Apparently that was the problem, because when I hooked up a lead from the tip AND the sleeve to the test pads and then connected the common test lead from my DMM to another ground on the pedal, I was suddenly able to measure the correct voltages on pin 6. What a relief.
Unfortunately, I'm still a beginner and learning as I go. Anyway, thanks for all your help and patience!
Also, on bsas's and yaka42's advice, I went through my build with an audio probe. Everything seems to be working properly, which is what made me think that I wasn't measuring correctly.
Quote from: jstone on February 23, 2017, 09:30:57 PM
Unfortunately, I'm still a beginner and learning as I go. Anyway, thanks for all your help and patience!
Learning is a positive thing. There is no need for the word "Unfortunately" in this context. Even though I didn't personally help on this one, I'll risk overgeneralizing:
We help because we enjoy helping, and we're patient because... well... it's the same darn reason! We enjoy helping. :icon_smile:
Quote from: EBK on February 24, 2017, 12:05:19 AM
Quote from: jstone on February 23, 2017, 09:30:57 PM
Unfortunately, I'm still a beginner and learning as I go. Anyway, thanks for all your help and patience!
Learning is a positive thing. There is no need for the word "Unfortunately" in this context. Even though I didn't personally help on this one, I'll risk overgeneralizing:
We help because we enjoy helping, and we're patient because... well... it's the same darn reason! We enjoy helping. :icon_smile:
No shame on learning man! It is part of the fun :D
For me, my build was perfect since the beginning but I unsoldered the C38 and solder something else and bounced my head over and over just because I didn't understood the limiter.
Quote from: bsas on February 05, 2017, 11:03:26 AM
The thing is that I found a 400mA adapter that is very small and white.
I like that it is white because then I will not mix with my DC adapter and burn my other pedals. And I like the size because of portability. I just want to know if 400mA is enough, I am not worried about price (specially on this build).
This is probably too late to help you, bsas, but I just finished a build, and measured the current draw @ 370 mA with the load resistors in place (RX3 and 4), or 322 mA without them. This is with Channel 2 active, Channel 1 draws about 5 mA less, and I'm using low-current LED's (around 1mA each).
Regards, Mike
Hi, Sorry to revive a dead thread but I'm having similar issues to those stated above (like the seemingly low voltages coming from pin 6 of IC10) but wasn't sure if I should make a whole new topic since this might help someone else who is as dumb as I am.
I originally had somehow fried a CA3080 when calibrating for the first time and had to wait a weekend for new ones to come. I swapped out the old for the new and everything seemed to work fine (including the compression) until I tried to calibrate it again and found that the voltages coming from PIN 6 of IC10 were really low. After taking a break for a bit i come back to find that the compressor is doing the same thing that bsas' originally did (with the compressor basically popping and muting and then slowly coming back)
Voltage wise I'm getting the same readings as bsas for IC9-12 and Q2 and Q3, but my 2n5457 is pretty different
I'm wondering if there is something wrong with my phone's output (im getting voltage readings that vary based on +/- dBs but It's never higher than 10-12). I'm using an iPhone 7->dongle->headphone cable with a piece of wire from the tip going to the + pad on near IC10 and a piece of wire from the sleeve that I've connected to both my cheapo DMM black lead and the ground on the pedal. The trimpot does change the voltages on pin 6 but it starts way too low in the first place. I've checked the resistors in the circuit, swapped some of the ICs and transistors for new ones, and tried to verify all the caps in the area of the circuit. I've been pulling my hair out over this one, w/o compression everything sounds amazing, but I just can't the compressor to work.
I'm hoping that I'm just making some incredible newbie error (went in over my head with this one) and that someone might be able to kick me in the right direction.
Another apology for exhuming an old thread.
I've finished my L5 build, and everything is working first try. It does run a bit hot so I need to put in some lower-current LEDs, but that's NBD.
Here's my question. I dialed in the clipping trimpot as described in the docs and on this thread but it occurs to me that the 4.4V target on IC10 pin 6 is not specified as RMS or peak-to-peak. I used RMS and it sounds reasonable, but I'd be interested to know what others have done.