DIYstompboxes.com

Hi,
This is a separation from @Wook22's thread https://www.diystompboxes.com/smfforum/index.php?topic=129191.0 (https://www.diystompboxes.com/smfforum/index.php?topic=129191.0) that I felt I was hogging too much for my own problem.
The symptoms are quite similar, and the builds are quite similar.
My original problem was that when I turn up Ratio towards 3 o'clock and Threshold around 9, there is a distorted sound. Not quite like a good distortion pedal but imho worse.
I started a thread for help here https://forum.pedalpcb.com/threads/thumb-sucker-compressor-scrapy-sound.10516/ (https://forum.pedalpcb.com/threads/thumb-sucker-compressor-scrapy-sound.10516/) back in early February and I got some good hints that I tried out. But the problem remains. The link also have photos and a sound sample of what I mean by distorted sound.
There is also a sense that Attack and Release does very little, but that could be a secondary fault to the first one.

Then it went in to hiatus until I found @Wook22 had a similar issue, so I piggy backed that thread for a while, but now it's time to make a separate thread.
The schematics are here
(https://i.postimg.cc/8sbx9D7n/2022-06-02-21-06-44-Thumb-Sucker.png) (https://postimg.cc/8sbx9D7n)
And if you want the pcb and zoom in the schematics the build pdf is here https://www.pedalpcb.com/docs/ThumbSucker-PedalPCB.pdf (https://www.pedalpcb.com/docs/ThumbSucker-PedalPCB.pdf)
And not to worry, although there are pictures in the linked other forum I will produce new ones.

I have recently re-heated all solder joints.
I have traced the connectivity on legs as much as possible trying to avoid direct solders when possible.
I tried to measure the components on the board, which checked out except for:
Threshold B1M
Ratio A1M
R101 and R102
D100 hard to get some sensible reading.
I swapped out C5 and C6 from Electrolytes to Film MKT. Forgot I had and swapped back to Electrolytes despite I had then learned it should not matter. And it didn't. Wish I hadn't swapped back. (And had better memory.)
I installed a trim for R10, and it is set to ~1k
The VREF and VCC plus ground all measure ok.
All reading further down.

What I have done:

Swapping TL072s and LM13700
Since there are two in this build I can swap them. No change. Later on I measured pin 7 on IC2 and it was zero, swapped again and now pin7 on the new IC2 got a reading. And so did the other pin7. Probably irrelevant or not pushed hard enough in the socket. Just mentioning.
I also got an opportunity to check another LM13700 from my friends Engineer's Thumb build and no change in my build regardless of LM, and his build sounds just fine.

Swapping the 2N3906
I tried with other PNPs and with an old Germanium one the distortion is much less. But not gone. The hfe of this Ge was quite low, so I doubt it is a "fix", but more of reducing symptoms.

Trying two JRC 4562
Supposed to be less noisy, I tried with these and it reduced the distortion. In combo with the PNP. Plus using 18V I felt that the problem was almost enough "smoothed out", but turning some knobs the distortion appeared again but with other settings. Not as loud, but still there. So this also feels like a way to lessen the symptoms without finding or fixing the problem.

Probing
It is clean until I hit IC1. Pin 3 is fine, but pin 2 and 1 (more loud) are distorted, as well as the C2 after. So stopped there.
The Threshold pot Pin 3 is fine, pin1 to VREF is quite silent and pin 2 sort of ok. IC2 pin 3 fine, pin2 slight sparkle, pin 1 bad, but nowdays very bassy. D1 Kathode is fine but slightly sparkly, R3 too and leg 1 on Release pot. But the other legs on Release are bassy distorted. The D1 anode and D2 are bad.

Small caps parallel with D1
On recommendation I tried 47pF, 82pF and 120pF, but no real change. Feels more like the category of trimming a circuit than trying to find the root cause for the distortion.

Scope trials
Got a tone generator and a 1-channel scope to probe around, and it was a clear flat top of the signal wave. But not the bottom of it. Might explain why this distortion sounds different than a pedal intended for that purpose.

3mm LEDs
For a while I thought they were causing problems since one of them measured really flimsy values but the other firm.
And they both shone quite bright. Until I swapped the ICs again, then back to "quiet" and the dodgy one stopped being that.

with looper/signal         only power no signal     
feed   VCC    Vref          feed   VCC    Vref
9.10   8.91   4.45          9.10   8.90   4.45

IC1                                IC1     
4.8-5.06  8.91                4.55   8.90   
4.46        4.45                4.46   4.45   
4.07        4.36 rising       4.08   4.43   
0.0          4.35 dropping  0.00   4.43   


IC2                           IC2     
4.50   8.91                4.66   8.89   
4.46   3.9-4.7            4.44   3.88   
4.27   4.43                4.26   4.43   
0.0     4.25                0.0     4.25   


IC3                         IC3           
1.10   0.0                1.35   0.0   
0.0     0.0                0.16   1.69   
4.46   0.0                4.43   1.45 jumpy 0.25   
4.45   0.0                4.44   0.36   
4.47   0.0                4.45   0.31   
0.0     8.91              0.0     8.89   
0.0     0.0                0.0     0.0   
0.0     0.0                0.0     0.0   

     PNP                   PNP
C   1.16                  1.20     
B   3.9-4.7              3.85     
E   4.45                  4.38   

Next steps
Will probably put back the C5 C6 as Film Caps MKTs again. Feel it got worse with electrolytes.
During my testing I have never really gotten much change out of Attack and Release. And sometimes the way the compression is released when the tone fades it come on very obvious and not smooth at all. So this together makes me wonder about if this circuit will ever contribute to the pedal chain,
But during the swap-fest yesterday I had some moment of clarity when all remedies were working toward a greater common good. Then it felt just fine and worth all these efforts. I touched a knob and the scraping came back in some places and others not. I fiddled mostly with Threshold and Release when this happened.
I've just about suspected everything, re-heated/soldered all and some twice and maybe more.
I have a hard time accepting the design should be faulty as such considering it is a popular pedal and others did not have my issue.
The problem solver in me wants to find out what the problem is. Would be a boost of morale if nothing else.
And I have had great help in this forum before.
But I am also nearing the point where I would order another kit and start fresh. I have knobs and drilled box, so that is worth a try.
Or just give up as the first one that failed on me. (OK I re-bought re-built an American 60's Fuzz Pro (?) (a Fuzzrite clone), but that was me destroying the board until it was just useless. 2nd build ever. I like to think I have evolved since...)
And either buy a good compressor from a shop or settle with the Zirconia (Diamond Comp clone) opto-comp that is quite nice.

Some pictures:

(https://i.postimg.cc/94LhC3bc/20220602-221418.jpg) (https://postimg.cc/94LhC3bc)

(https://i.postimg.cc/Y4ssdt8L/20220602-221427.jpg) (https://postimg.cc/Y4ssdt8L)

(https://i.postimg.cc/m1QpZC47/20220602-221431.jpg) (https://postimg.cc/m1QpZC47)

(https://i.postimg.cc/HrWvHrh7/20220602-221455.jpg) (https://postimg.cc/HrWvHrh7)

(https://i.postimg.cc/dDdx9PCD/20220602-221504.jpg) (https://postimg.cc/dDdx9PCD)

(https://i.postimg.cc/yDfQN7Mp/20220602-221538.jpg) (https://postimg.cc/yDfQN7Mp)

(https://i.postimg.cc/GHxgZFqC/20220602-221558.jpg) (https://postimg.cc/GHxgZFqC)

(https://i.postimg.cc/4mgFLLvP/20220602-221621.jpg) (https://postimg.cc/4mgFLLvP)

(https://i.postimg.cc/0KgHqZT8/20220602-221625.jpg) (https://postimg.cc/0KgHqZT8)

I built this version :

https://www.musikding.de/Engineers-Thumb-Compressor-kit

I have also some non-musical distortion appearing when the Treshold pot is going CCW, depending on how Ratio and Attack are set.

I have a fancy expensive compressor from Walrus, the Deep Six. There is also some sort of distortion when Sustain , Attack and Blend are fully CW.

I have the Meridian too, but it is kind of special, not like the usual compressor. But extreme settings will do extreme things to the signal...

I think it is normal, maybe depending on the pickups...

Both my guitars have two active hambuckers and I never tried my compressors with a passive single-coil pick up.

Are we sure this distortion issue is actually an issue ?  Many circuits need to be carefully adjusted, or they won't be very useful, compressors would be among them in my experience.

On mine, I just turn the Treshold control until the noises disappear.

Quote from: eh la bas ma on June 03, 2022, 10:37:59 AM
I built this version :

https://www.musikding.de/Engineers-Thumb-Compressor-kit

I have also some non-musical distortion appearing when the Treshold pot is going CCW, depending on how Ratio and Attack are set.

I have a fancy expensive compressor from Walrus, the Deep Six. There is also some sort of distortion when Sustain , Attack and Blend are fully CW.

I have the Meridian too, but it is kind of special, not like the usual compressor. But extreme settings will do extreme things to the signal...

I think it is normal, maybe depending on the pickups...

Both my guitars have two active hambuckers and I never tried my compressors with a passive single-coil pick up.

Are we sure this distortion issue is actually an issue ?  Many circuits need to be carefully adjusted, or they won't be very useful, compressors would be among them in my experience.

On mine, I just turn the Treshold control until the noises disappear.

Thanks,
All good points.
In my case I am convinced. The distortion happens early and on moderate settings. If I dial it "out" then there is basically no compression. So the "useful" area does not match the available area very much.
I compared with Eng Thumb build. Same settings, and Eng is fine, but mine distorts.
Also had replies to soundfiles in the thread on pedalpcb forum that tended to agree. With my settings. Low Attack and Release. Volume to stay at unity. Ratio noon to 3, Threshold 9 to noon. But now more all over.
If this was something I had bought, and the seller said it was as designed, I would have returned it.
But I am also aware of the extremes of this and other compressors can cause "bad" output, just wish there was any "good" in mine.

I would say the strength of the Engineer's Thumb is to get a more balanced sound when you play full chords, allowing to hear the lows and the highs more evenly. Other than that, besides the volume swell with the Release control, I think it's quite unoticeable.

If I want to really increase the attack when I do some fingerpicking for exemple, I use an other compressor able to do that well.

Quote from: eh la bas ma on June 03, 2022, 10:37:59 AM
Are we sure this distortion issue is actually an issue ?  Many circuits need to be carefully adjusted, or they won't be very useful, compressors would be among them in my experience.

You should be able to use a circuit with the controls in any position without something sounding terrible. Ok, certain settings are better than others, and extreme settings might not be that "musical", but the circuit should continue to function correctly. If  a compressor only works with the knobs within a certain range, either there's something wrong with it or the design isn't much good, in my view. So, yes, I think there's an issue.

We guitar players tend to forget that guitars do not put out smooth signals.  We rely on compressors to do that for us.  But the unevenness of the guitar signal means that there are unexpected peaks as a note seems to die out.  Of course, people will pay special attention to the decay phase of strummed guitar strings, because that is where we expect compressors to create "sustain", by electronically maintaining a steady level.  Paradoxically, it is during that decay phase where the signal level poses the most challenges.

Fifty years ago, I was studying for an exam in the student residence lounge and lying back on a bench seat.  As I looked out at students entering and leaving the building, from an upside down perspective, I couldn't help but notice that their gait was a LOT more uneven than I was accustomed to.  Normally, seeing people walk "rightside up" every day, one imposes perceptual smoothing and continuity in their movement, as if the actual bobbing up and down with each step (remember, that as you extend one leg/foot well in front of the other, you have actually shortened your height by a few inches, compared to standing straight) simply didn't happen.

The same is true of guitars (and probably many other instruments).  We PERCEIVE the decay as very smooth when it is actually very bumpy and glitchy.  Notice this when it comes to analog octave dividers using a 4013, where the signal falls unpredictably above and below the triggering/tracking threshold, and we notice this with noise gates whose gate-on threshold is set wrong.  When it comes to compressors that use a half-wave rectifier, the momentary fluctuations in compensating gain will show up if the decay of the rectifier is set too fast or too slow.  Indeed, the audible consequences of half-wave rectification in noise-gates, compressors, and auto-wahs is regularly reported by people as "distortion".

The Thumb-Sucker is not a bad design, but its use of an OTA driven by a half-wave rectifier makes the instantaneous response of the OTA susceptible to envelope ripple.  That's one of the good things about using LDRs in compressors and auto-wahs: they "smooth out the glitches" arising from half-wave rectifiers...at least if you let them.

The solution is usually either shortening the gain recovery time, so that one leaves ripple behind quickly, or lengthening gain-recovery time so that the circuit behaves like a slow-to-respond LDR.

Quote from: Mark Hammer on June 03, 2022, 01:34:34 PM
We guitar players tend to forget that guitars do not put out smooth signals.  We rely on compressors to do that for us.  But the unevenness of the guitar signal means that there are unexpected peaks as a note seems to die out.  Of course, people will pay special attention to the decay phase of strummed guitar strings, because that is where we expect compressors to create "sustain", by electronically maintaining a steady level.  Paradoxically, it is during that decay phase where the signal level poses the most challenges.

Fifty years ago, I was studying for an exam in the student residence lounge and lying back on a bench seat.  As I looked out at students entering and leaving the building, from an upside down perspective, I couldn't help but notice that their gait was a LOT more uneven than I was accustomed to.  Normally, seeing people walk "rightside up" every day, one imposes perceptual smoothing and continuity in their movement, as if the actual bobbing up and down with each step (remember, that as you extend one leg/foot well in front of the other, you have actually shortened your height by a few inches, compared to standing straight) simply didn't happen.

The same is true of guitars (and probably many other instruments).  We PERCEIVE the decay as very smooth when it is actually very bumpy and glitchy.  Notice this when it comes to analog octave dividers using a 4013, where the signal falls unpredictably above and below the triggering/tracking threshold, and we notice this with noise gates whose gate-on threshold is set wrong.  When it comes to compressors that use a half-wave rectifier, the momentary fluctuations in compensating gain will show up if the decay of the rectifier is set too fast or too slow.  Indeed, the audible consequences of half-wave rectification in noise-gates, compressors, and auto-wahs is regularly reported by people as "distortion".

The Thumb-Sucker is not a bad design, but its use of an OTA driven by a half-wave rectifier makes the instantaneous response of the OTA susceptible to envelope ripple.  That's one of the good things about using LDRs in compressors and auto-wahs: they "smooth out the glitches" arising from half-wave rectifiers...at least if you let them.

The solution is usually either shortening the gain recovery time, so that one leaves ripple behind quickly, or lengthening gain-recovery time so that the circuit behaves like a slow-to-respond LDR.

Thanks. Most interesting indeed. Will probably have to digest it a bit more to let it sink in.
And yes compressors seem to me more and more as an area where "it comes together" in many aspects. So I am learning and digesting all I can.

Still, it sounds really crappy compared to others I've heard. Considering the many buyers and users, it just has to be something in my unit that is different.
I fell I have just about suspected everything. Possibly the pots themselves remain.
Take them off each one and test their reaction to turn to look for anything out of the expected perhaps.
I was contemplating removing the LEDs at the beginning of the signal path, but there is no distortion there yet, so not sure.

Quote from: ElectricDruid on June 03, 2022, 12:20:35 PM

Quote from: eh la bas ma on June 03, 2022, 10:37:59 AM
Are we sure this distortion issue is actually an issue ?  Many circuits need to be carefully adjusted, or they won't be very useful, compressors would be among them in my experience.

You should be able to use a circuit with the controls in any position without something sounding terrible. Ok, certain settings are better than others, and extreme settings might not be that "musical", but the circuit should continue to function correctly. If  a compressor only works with the knobs within a certain range, either there's something wrong with it or the design isn't much good, in my view. So, yes, I think there's an issue.

Thanks and yes, that is my thinking as well. And the design should hold as far as others have witnessed.
Unless I get some good hints on specifics to try out, I will have to decide if I should get another same kit and hope to get it right a second time.
As I just wrote above, I could try the pots, but I feel I have tried most things.
And can't see anything that screams out from the readings.
I could measure the diodes A and K as well, but no idea what I should expect there.

Try a larger value for C6, like 2u2 or even 4u7, and see if that improves anything.

Quote from: Mark Hammer on June 03, 2022, 02:40:32 PM
Try a larger value for C6, like 2u2 or even 4u7, and see if that improves anything.

Thanks.
OK, will do. However it is a bit along the lines of tweaking or workarounding IMHO. And here I also have 18V, other more low-noise ICs, Films for C5 and C6 and different PNPs to work with as well.
And even if I get it to a good and useful level, I'd be happy of course, but still want to learn what I had done wrong in the first place. It is bordering to being "personal" with the pedal almost...
If I do not find the problem I am tempted to getting another kit, breaboard it (yes, should have done that in the first place) and build it and then run them "half/half" if possible until I find the culprit.

Tried a 100n cap (ceramic or film) or 2 or even 3 across the power-pins of the opamps/OTA yet? (In fact in parallel to C100, but closer to the IC-pins). And/or maybe 1 in parallel to C101?

Just as a point of reference, both the PedalPCB, and Musikding schematics in this thread omit the 1k resistor from the OTA output to the inverting input of the gain opamp relative to the OG version:

http://www.valvewizard.co.uk/engineersthumb.html

Quote from: puretube on June 05, 2022, 06:08:29 AM
Tried a 100n cap (ceramic or film) or 2 or even 3 across the power-pins of the opamps/OTA yet? (In fact in parallel to C100, but closer to the IC-pins). And/or maybe 1 in parallel to C101?

Thanks
No not yet. Plan to try @Mark Hammer's suggestion for C6. Then I can try this.
Still, even if it helps, it would not find the root cause?
Unless of course the design is flawed.

Quote from: idiot savant on June 05, 2022, 07:26:29 AM
Just as a point of reference, both the PedalPCB, and Musikding schematics in this thread omit the 1k resistor from the OTA output to the inverting input of the gain opamp relative to the OG version:

http://www.valvewizard.co.uk/engineersthumb.html

The one between Ratio and Treble Boost mod?
Do you think not having it it could be the reason for my distortion problem?

Current plan is to try the various suggestions here and in another thread.
Perhaps with all the swaps and mods as well.
But I think I will breadboard with spare parts as much as possible and take from this build the rest to see if it flies at all. Might lead to a new pcb though, or perf board co sidering my limited finesse and high "development potential" when it comes to soldering...

Quote from: matopotato on June 05, 2022, 07:30:41 AM
Still, even if it helps, it would not find the root cause?
Unless of course the design is flawed.

From my perspective, sometimes the root cause is the guitar signal itself.  We THINK it is smooth and steady, but it isn't.  It's very erratic.  The challenge, when it comes to compressor design, is to turn the erratic INTO "the smooth" with as few parts and stages as possible.  If one skimps a bit and thinks "There, THAT should be enough to do the job", that's not a design "flaw"

Quote from: Mark Hammer on June 05, 2022, 08:48:28 AM

Quote from: matopotato on June 05, 2022, 07:30:41 AM
Still, even if it helps, it would not find the root cause?
Unless of course the design is flawed.

From my perspective, sometimes the root cause is the guitar signal itself.  We THINK it is smooth and steady, but it isn't.  It's very erratic.  The challenge, when it comes to compressor design, is to turn the erratic INTO "the smooth" with as few parts and stages as possible.  If one skimps a bit and thinks "There, THAT should be enough to do the job", that's not a design "flaw"

Thanks!
FWIW, I have the issue with both humbuckers and single coils.
Perhaps my thinking that "if it is a kit with good reviews, then there must be a findable root cause with a fix by changing faulty component" is the flaw, at least for compressors.
I tend to rationalize something I thought was very binary, but as you are making me see, it is not. I just have to get that "paradigm shift" into my mind.

Quote from: idiot savant on June 05, 2022, 07:26:29 AM
Just as a point of reference, both the PedalPCB, and Musikding schematics in this thread omit the 1k resistor from the OTA output to the inverting input of the gain opamp relative to the OG version:

http://www.valvewizard.co.uk/engineersthumb.html

Good find! But then,  in his version 2 (2016) the Valve Wizard omitted it there, too ...
http://www.valvewizard.co.uk/engineersthumb2.html (http://www.valvewizard.co.uk/engineersthumb2.html)

Quote from: puretube on June 05, 2022, 06:08:29 AM
Tried a 100n cap (ceramic or film) or 2 or even 3 across the power-pins of the opamps/OTA yet? (In fact in parallel to C100, but closer to the IC-pins). And/or maybe 1 in parallel to C101?

Ok, so I tried 100n and also 220n across pin4 amd 8. No change or effect either way.
Also on C101 but no effect.
Was the expected result that the dist would go away, or be reduced?
Thanks for suggesting though, appreciate it.

Quote from: Mark Hammer on June 03, 2022, 02:40:32 PM
Try a larger value for C6, like 2u2 or even 4u7, and see if that improves anything.

Ok, so I have original electolyte 1uF at C6. Instead of desoldering, I took another 1uF i parallel. I imagined it would be the same as a 2uF cap.
Interesting effect: Pop, LEDs flashed, then silence. And then gradually build up.
The tone was very bassy, so most of the tone gone. And the bassy still had the distortion. (Got some fuzz feeling sort of).
So I did not go with 4,7uF as I doubt it would improve.
Thanks for the suggestion regardless.

Attempted to swap the C5 C6 from electrolyte to Film, but I feel te eyelets have just about had enough of my attempts.
So new plan is to breadboard with whatever spares I have.
Using the ICs, transistor and at least one pot.
Not sure what I will do with any result though. I guess I want to know if the kit will work for me. And how it sounds.

The OTA input is prone to clipping. R7 and R6 form a voltage divider to reduce the signal level to avoid clipping. Measure the values of those resistors to confirm they are correct. You could try increasing R7 above 10k to reduce the signal level the OTA has to pass.

Quote from: anotherjim on June 06, 2022, 04:35:31 AM
The OTA input is prone to clipping. R7 and R6 form a voltage divider to reduce the signal level to avoid clipping. Measure the values of those resistors to confirm they are correct. You could try increasing R7 above 10k to reduce the signal level the OTA has to pass.

Thanks. Wasn't aware of that.
Seems OTA in compressor has a few less desirable side effects.
R7 9,78k and R6 218R, so they check out. But if R7 could be increased if anything, then currently being below 10k is not helping I guess.

Quote from: matopotato on June 05, 2022, 01:22:26 PM

Quote from: puretube on June 05, 2022, 06:08:29 AM
Tried a 100n cap (ceramic or film) or 2 or even 3 across the power-pins of the opamps/OTA yet? (In fact in parallel to C100, but closer to the IC-pins). And/or maybe 1 in parallel to C101?

Ok, so I tried 100n and also 220n across pin4 amd 8. No change or effect either way.
Also on C101 but no effect.
Was the expected result that the dist would go away, or be reduced?
Thanks for suggesting though, appreciate it.

Just to avoid any rubbish on the power-/vref-rails (be it from the circuit itself, or from outside) entering sensitive points in the circuit ... (despite the good PSRR of modern ICs).

Another thought: How about swapping the position of R8 & C4?
(i.e.: instead of the opamp directly driving a 10µ cap which is grounded through 11k,
having the opamp driving the cap, which is grounded through 10k, via 1k).
The Valve-Wizard did that in his Version 2, too.

Bingo?

Quote from: puretube on June 06, 2022, 07:10:51 AM
Another thought: How about swapping the position of R8 & C4?
(i.e.: instead of the opamp directly driving a 10µ cap which is grounded through 11k,
having the opamp driving the cap, which is grounded through 10k, via 1k).
The Valve-Wizard did that in his Version 2, too.

Bingo?

Thanks for the idea.
Right now I am breadboarding a copy but same IC and transistor plus one B1M pot. (Which ripped en eyelet, so original build is drifting slowly towards "don't know why" land)
Will try to test your suggestion somehow. If breadboarding still does distort, I will try this.

Quote from: anotherjim on June 06, 2022, 04:35:31 AM
The OTA input is prone to clipping. R7 and R6 form a voltage divider to reduce the signal level to avoid clipping. Measure the values of those resistors to confirm they are correct. You could try increasing R7 above 10k to reduce the signal level the OTA has to pass.

Like 12k or 15k? Or higher still?

If you want to try it on your PCB version, lift one end of the 10k and connect it in series with a pot. Tweak and see. If it works, take the pot out of circuit then measure it and add a resistor of the pot value or next value up.

I've a hunch that (if this is the problem) 22k instead of the 10k may be the charm, but swapping resistors to find perfection soon gets tedious so a 50k or 100k pot should give enough range to try.

Quote from: anotherjim on June 06, 2022, 01:32:40 PM
If you want to try it on your PCB version, lift one end of the 10k and connect it in series with a pot. Tweak and see. If it works, take the pot out of circuit then measure it and add a resistor of the pot value or next value up.

I've a hunch that (if this is the problem) 22k instead of the 10k may be the charm, but swapping resistors to find perfection soon gets tedious so a 50k or 100k pot should give enough range to try.

Thanks. Got to 15k but heard no difference. Will try with a trim after the 10k. But I no longer have very high hopes.

Now I have breadboarded the Thumb Sucker using other units I had in my "stash".
Bottom line: Sounds same as before. https://soundcloud.com/user-558594533/thumbsuckerscrapy-1?utm_source=clipboard&utm_medium=text&utm_campaign=social_sharing (https://soundcloud.com/user-558594533/thumbsuckerscrapy-1?utm_source=clipboard&utm_medium=text&utm_campaign=social_sharing) Distorts still. Cannot dial it out.

I tried swapping one of the OpAmps for a spare one, and felt it made a difference, but after rotating all three around I would say it makes no difference.
For a bit it sounded clean and nice, but not much of compression. Turns out I had forgotten to connect a few pins on the OTA LM13700.
Then it went back to the same distorted. Even sounded like a Fuzz for a while.

I tried my favorite "improvements" by using jrc 4562 for OpAmps, 18V for more headroom thus handling more of "distortion" before it breaks through, PNP with half and double hfe values.
Nothing made a difference this time. Sadly, since that was an alternative earlier.

I tried the swap of R8 and C4 suggested by @puretube, but sadly it had no effect.

I also tried R7 at 12k and 15k as suggested by @anotherjim, and still no change.

I have had it tried 200 miles away, so I doubt my house, room etc play a big role in this.
I run it with Strat Single Coils to Marshall DSL40CR. Have tried with humbuckers as well, but same bad.

I did "reuse":
the 3 ICs, and swapped OpAmps around as mentioned.
the PNP transistor and swapped around.
the Threshold B1M pot, but put it as the Release instead, so if that would have been the culprit I would have expected a different bad when in a different position.

So the only thing on the breadboard that is equal to the kit build is the OTA, LM13700.
On the other hand I tried another LM13700 in the build last weekend (the rest being the same) and it did not change anything, so I ruled it out.

To summarize, I feel I have swapped everything at least once, and in my humble opinion something should have changed...
I am very happy for all suggestions, but only one did some change, but to the worse sort of, although it was kind of fun (2uF for C6).
I thought breadboarding would make it fly and play properly. I would then have de-soldered and replaced one by one the components on the breadboard with one from the original kit until the offender revealed itself.
Then get a new pcb and re-build from the breadboard.
Or get a new kit with everything, but from today's tests I do not feel confident that it surely would work. And then I would have wasted another $50-ish.

I build a Zirconia from Lectric-FX, an optical compressor, and that is very nice. A certain smoothness to it as @Mark Hammer mentioned.
I was hoping to build something similar to Keeley Compressor/MXR Dynacomp/Ross compressor and felt the Thumb Sucker would fit that bill.
Anyone with some alternative build to the Thumb Sucker but that would be like Keeley preferably?

Quote from: anotherjim on June 06, 2022, 01:32:40 PM
If you want to try it on your PCB version, lift one end of the 10k and connect it in series with a pot. Tweak and see. If it works, take the pot out of circuit then measure it and add a resistor of the pot value or next value up.

I've a hunch that (if this is the problem) 22k instead of the 10k may be the charm, but swapping resistors to find perfection soon gets tedious so a 50k or 100k pot should give enough range to try.

Thanks, it was an interesting thing to try.
I put the 10k back on the board an added a 50k trimmer together with it. So I could dial 9.7k to 59k (ish). Sadly there was no change in the distorted sound. It gave an overall volume boost though.
Even though I have tried similar idea in other builds, it just did not strike me until you suggested it. I hope to learn by now using trimmers and pots in areas where a changed R could make a difference.

Quote from: Mark Hammer on June 03, 2022, 01:34:34 PM
When it comes to compressors that use a half-wave rectifier, the momentary fluctuations in compensating gain will show up if the decay of the rectifier is set too fast or too slow.  Indeed, the audible consequences of half-wave rectification in noise-gates, compressors, and auto-wahs is regularly reported by people as "distortion".

The Thumb-Sucker is not a bad design, but its use of an OTA driven by a half-wave rectifier makes the instantaneous response of the OTA susceptible to envelope ripple.  That's one of the good things about using LDRs in compressors and auto-wahs: they "smooth out the glitches" arising from half-wave rectifiers...at least if you let them.

The solution is usually either shortening the gain recovery time, so that one leaves ripple behind quickly, or lengthening gain-recovery time so that the circuit behaves like a slow-to-respond LDR.

So If i understand correctly, this contradicts what ElectricDruid told us ?

"You should be able to use a circuit with the controls in any position without something sounding terrible. Ok, certain settings are better than others, and extreme settings might not be that "musical", but the circuit should continue to function correctly. If  a compressor only works with the knobs within a certain range, either there's something wrong with it or the design isn't much good, in my view. So, yes, I think there's an issue."

Edit : From project documentation : "Release- The time it takes for the gain to recover after the loud sound has passed."

Looks like Release is the "gain-recovery time" control.

So, according to Mark, the Release control should be the key to stop the circuit from distorting the signal ? However, only Ratio or Threshold can do that, Release set anywhere CW doesn't change anything about the distortion, and CCW it makes it worse, at least on my build...

Last attempt: take out the two red LEDs near the input, or increase that input-series-resistor from 1k to 4k7 or 10k. Voila!

Quote from: puretube on June 06, 2022, 04:50:39 PM
Last attempt: take out the two red LEDs near the input, or increase that input-series-resistor from 1k to 4k7 or 10k. Voila!

Thanks.
Ok, will try the increase. I already tried pulling the LEDs. No change.

Quote from: eh la bas ma on June 06, 2022, 04:34:26 PM

Quote from: Mark Hammer on June 03, 2022, 01:34:34 PM
When it comes to compressors that use a half-wave rectifier, the momentary fluctuations in compensating gain will show up if the decay of the rectifier is set too fast or too slow.  Indeed, the audible consequences of half-wave rectification in noise-gates, compressors, and auto-wahs is regularly reported by people as "distortion".

The Thumb-Sucker is not a bad design, but its use of an OTA driven by a half-wave rectifier makes the instantaneous response of the OTA susceptible to envelope ripple.  That's one of the good things about using LDRs in compressors and auto-wahs: they "smooth out the glitches" arising from half-wave rectifiers...at least if you let them.

The solution is usually either shortening the gain recovery time, so that one leaves ripple behind quickly, or lengthening gain-recovery time so that the circuit behaves like a slow-to-respond LDR.

So If i understand correctly, this contradicts what ElectricDruid told us ?

"You should be able to use a circuit with the controls in any position without something sounding terrible. Ok, certain settings are better than others, and extreme settings might not be that "musical", but the circuit should continue to function correctly. If  a compressor only works with the knobs within a certain range, either there's something wrong with it or the design isn't much good, in my view. So, yes, I think there's an issue."

Edit : From project documentation : "Release- The time it takes for the gain to recover after the loud sound has passed."

Looks like Release is the "gain-recovery time" control.

So, according to Mark, the Release control should be the key to stop the circuit from distorting the signal ? However, only Ratio or Threshold can do that, Release set anywhere CW doesn't change anything about the distortion, and CCW it makes it worse, at least on my build...

Thanks,
I'll leave it to the ones you mention to comment on contents.
My observation of the distortion is that turning knobs had no or little impact. Of course zero Ratio made the distortion almost go away, but so did any compression. And volume close to zero, but again, not useful.

Quote from: matopotato on June 06, 2022, 05:17:11 PM

Quote from: puretube on June 06, 2022, 04:50:39 PM
Last attempt: take out the two red LEDs near the input, or increase that input-series-resistor from 1k to 4k7 or 10k. Voila!

Thanks.
Ok, will try the increase. I already tried pulling the LEDs. No change.

Okay - I give up  :icon_sad: (until I`ll try a build, one day ... - with 30 years old NOS chips).

I just tried. No luck...

First I changed R1 1k to 10k, same. Then I desoldered both leds : still distorting, no change.

Matopotato, Wook22, i am curious to know if you listened to the sound clip I posted ? Do you have a similar distortion with the settings shown on the picture, or do we have a different symptom ?

https://soundcloud.com/ehlabas-ma-chaussure/engineersthumb-distortingwav-1

Quote from: eh la bas ma on June 06, 2022, 05:35:16 PM
I just tried. No luck...

First I changed R1 1k to 10k, same. Then I desoldered both leds : still distorting, no change.

Matopotato, Wook22, i am curious to know if you listened to the sound clip I posted ? Do you have a similar distortion with the settings shown on the picture, or do we have a different symptom ?

https://soundcloud.com/ehlabas-ma-chaussure/engineersthumb-distortingwav-1

Sort of, I think so. Check link in #30 above.
Some have mentioned earlier that if you go full on Ratio and almost zero on Threshold then there will be distortion.
But for me it happens a lot earlier.
A bit discouraging that you have the same issue. Then little or no point getting another kit.

Edit: did you have the settimgs as in the soundclip picture throughout?
Mine might be more obvious on the bass strings, or full chord.

Quote from: puretube on June 06, 2022, 05:25:37 PM

Quote from: matopotato on June 06, 2022, 05:17:11 PM

Quote from: puretube on June 06, 2022, 04:50:39 PM
Last attempt: take out the two red LEDs near the input, or increase that input-series-resistor from 1k to 4k7 or 10k. Voila!

Thanks.
Ok, will try the increase. I already tried pulling the LEDs. No change.

Okay - I give up  :icon_sad: (until I`ll try a build, one day ... - with 30 years old NOS chips).

Sorry. Still I really appreciate very much your suggestions!
Will try the R increase since it is breadboarded, but as @eh la bas ma tried it below, it might not help.

see eh la bas ma`s latest thread ...
https://www.diystompboxes.com/smfforum/index.php?topic=129237.new#new (https://www.diystompboxes.com/smfforum/index.php?topic=129237.new#new)

:icon_question:

Quote from: puretube on June 07, 2022, 05:14:04 AM
see eh la bas ma`s latest thread ...
https://www.diystompboxes.com/smfforum/index.php?topic=129237.new#new (https://www.diystompboxes.com/smfforum/index.php?topic=129237.new#new)

:icon_question:

Thanks, very interesting. Will try

Quote from: puretube on June 07, 2022, 05:14:04 AM
see eh la bas ma`s latest thread ...
https://www.diystompboxes.com/smfforum/index.php?topic=129237.new#new (https://www.diystompboxes.com/smfforum/index.php?topic=129237.new#new)

:icon_question:

Ok, disconnected pin 8 and 9 to ground so that they are unconnected to anything.
No change in the distortion. Tried on off to be sure and it had no effect on the output as far as I can tell.
Even joined them to eachother but not to ground.
Still closer to a Fuzz than a Compressor sadly. Cleans up with guitar volume even...

Quote from: matopotato on June 07, 2022, 01:24:42 AM
Then little or no point getting another kit.

I agree...

Quote from: matopotato on June 07, 2022, 01:24:42 AM
Edit: did you have the settimgs as in the soundclip picture throughout?
Mine might be more obvious on the bass strings, or full chord.

Maybe that's because your pickups are closer to the bass strings or something...

The soundclip is a short loop, with 3 repeats :

first, clean guitar.

Then, settings as shown on the picture.

Finally, Theshold fully CCW, Ratio fully CW, Release fully CCW . These are the settings with the worse distorted signal possible with my build.

Quote from: eh la bas ma on June 07, 2022, 10:05:57 AM

Quote from: matopotato on June 07, 2022, 01:24:42 AM
Then little or no point getting another kit.

I agree...

Quote from: matopotato on June 07, 2022, 01:24:42 AM
Edit: did you have the settimgs as in the soundclip picture throughout?
Mine might be more obvious on the bass strings, or full chord.

Maybe that's because your pickups are closer to the bass strings or something...

The soundclip is a short loop, with 3 repeats :

first, clean guitar.

Then, settings as shown on the picture.

Finally, Theshold fully CCW, Ratio fully CW, Release fully CCW . These are the settings with the worse distorted signal possible with my build.

Thanks.
I was told that the fully dimed extremes might cause distortion, so I have had mine on
Attack and Release, close to CCW but not fully in the bottom.
Ratio from noon to 3 o'clock or almost full CW, Distortion all the way now, before less at noon and most at full, but now seems bad regardless
Threshold first between noon and 9 o'clock and at 9 bad enough in combination with Ratio. Nowdays the Threshold seems to have less impact.
Volume seems to be doing its thing and would not say it has an impact.

@duck_arse:

Some attempt at updated reading with breadboarded using only TL072 x 2 and LM13700 from original build.
Plus one B1M pot, but for different circuit location (i.e. no longer prime suspect)

IC1
4,65   8,83
4,42   4,40
4,02   4,27
0,00   4,20


IC2 got some variations, this was the latest read
4,30  8,84
4,46  2,69
4,0    2,02
0       --- falling

IC3 (LM13700)
1,09   0,00
0,3     0,16
4,43   1,3
4,43   0,20
4,43   0,20
0        8,84
0        0
0        0
This was before degrounding them

PNP
C: 1,13
B: 4,8
E: 4,45

Quote from: matopotato on June 06, 2022, 02:17:55 PM

Quote from: anotherjim on June 06, 2022, 01:32:40 PM
If you want to try it on your PCB version, lift one end of the 10k and connect it in series with a pot. Tweak and see. If it works, take the pot out of circuit then measure it and add a resistor of the pot value or next value up.

I've a hunch that (if this is the problem) 22k instead of the 10k may be the charm, but swapping resistors to find perfection soon gets tedious so a 50k or 100k pot should give enough range to try.

Thanks, it was an interesting thing to try.
I put the 10k back on the board an added a 50k trimmer together with it. So I could dial 9.7k to 59k (ish). Sadly there was no change in the distorted sound. It gave an overall volume boost though.
Even though I have tried similar idea in other builds, it just did not strike me until you suggested it. I hope to learn by now using trimmers and pots in areas where a changed R could make a difference.

You tried changing the voltage divider ratio at the OTA inputs from 220R : 10k  to  220R : 59k  and managed to get a volume boost.

Just imagine what taking that ratio to its limit  (for example by shorting out the 220R) would do.
The OTA would then have no input signal (because the two inputs would be shorted together) and so the OTA would give no output current.
In other words it would look like an infinite feedback resistance in the opamps loop, so the gain would be massive and give distortion.

The same thing goes for my (not well thought out) suggestion of trying to increase the resistance on the PNP emitter.  The bigger you make that emitter resistance, the lower the OTA output current will be, so the OTA will act like a bigger resistor in the opamp's feedback loop, and so give distortion.

If the distortion we are trying to solve is due to the OTA looking like too big a resistor (due to it giving out too little current) then I would

1) Leave the 1k resistor on the PNP emitter alone.  Certainly do not lower it or you could kill the OTA if you are not careful.
2) Try to decrease the 10k resistor in the divider at the OTA input, not increase it as you tried above. Easiest way to experiment is to add resistance  in parallel to it. Try add 47k in parallel to the 10k (which effecively turns the 10k into an 8k2). If 47k does not help much try 22k instead.

If the distortion problem is due to the OTA acting like an infinite resistor (i.e. sometimes giving zero output current) and this happens while strumming hard (i.e. despite the input control current to the OTA being large), then the only way I can see for that to happen is that the OTA input signal is zero. That's because 
          OTA output current = OTA input signal * Transconductance determined by control current

The opamp responsible for the circuit gain might have a DC output voltage that is not exactly at the bias voltage (due to opamp imperfections), but the scaling resistors at the OTA input are referenced to the bias voltage.  I am wondering if such a mismatch would be a problem ?

You can imagine an extreme case when the difference between those two DC voltages is large.
So a sinusoidal signal at the opamp output would get scaled down to give an OTA input signal with a non-zero offset.
In an extreme case, you could imagine that the OTA input signal (i.e. the voltage between the two OTA inputs)
looks like a sinusoid that is always negative and just touches zero at its peaks, rather than being a sinusoid that oscillates about zero.
In that extreme case, the OTA would act like an infinite resistor (i.e. give no output current) for the very top of the sinusoid where it touches zero, but at the bottom of the sinusoidal it would be acting like a smaller resistor (and give output current).
So the top and bottom of the sinusoid would be treated differently.
For the OTA to act like a resistor, I think we'd want the top and bottom of the sinusoid to be treated in the same way (i.e.  produce equal and opposite OTA output currents).  They would be treated in the same way if there was no mismatch in the DC levels.

Maybe this simplistic thinking is not correct and mismatch in DC levels is not a problem?

So if DC offset could be a problem (and I dont know if it is) then maybe block the DC ?

What would happen if instead of tying the opamp output direct to the scaling resistors at the OTA input, a large capacitor (many uF) is used there instead to let the signal through but block any mismatch in DC.

If we think of OTA inputs like they were opamp inputs, then we only need one of the inputs to set the input bias voltage.  Not both of them.  Just a thought.


matopotato:  Try this.  The 10k resistor that is part of the 220R : 10k scaling resistor section at the OTA input.  Disconnect that 10k resistor from connecting directly to the opamp output, and instead connect it to the opamp output through a 10uF capacitor.   Before disconnecting anything though, measure the voltage at the opamp output and see if it is larger or smaller than the bias voltage.  The capacitor will probably be electrolytic and you want to orient it so that its +ve end is connected to the higher voltage.

Thanks a lot @DrAlx,
I will try the 10k with 47k in //.

And also the 10k plus a 10uF cap. If I first measure voltage on the OTA connecting pin and then the other side of 10k, and set minus of 10uF to the lower potential, the is "safe"?

I DO read what you wrote, but have to confess that my electronics understandings are quite limited.
Both from functional aspects (but learning every day) as well as physics/theoretical aspects (started reading in semiconductors though, so given enough time..)
I really appreciate the effort you put in.
Again thanks.

Write the voltages on the circuit diagram
You have given us conflicting voltages on the same wire. How can IC1 pins 6 & 7 give different readings when they are shorted?
IC2 pins 6 & 7 are way low, they should be at Vref or higher when idle. Either IC2 pins are connected wrong or something in the side chain is incorrect (backward diode?).
(https://i.postimg.cc/23Y0wmTV/2022-06-02-21-06-44-Thumb-Sucker.jpg) (https://postimg.cc/23Y0wmTV)

Conflicting voltages or unstable power supply?
Hmmm....

QuoteIC2 got some variations, this was the latest read
4,30  8,84
4,46  2,69
4,0    2,02
0       --- falling

pin 5 falling would indicate the rectifier had input signal applied. 2V69 at pin 7 would mean "compressing". but not while you have 4 something volts that should be coming from pin 1. I think.

[edit :] deleted - see reply #69.

Quote from: matopotato on June 08, 2022, 10:22:02 AM
If I first measure voltage on the OTA connecting pin and then the other side of 10k, and set minus of 10uF to the lower potential, the is "safe"?

Correct. I would try that capacitor change on its own, leaving the resistor at a value of 10k.
EDIT:  If the voltages written on the circuit diagram are correct, the + side of the 10uF cap should connect to the opamp output, and the - side of the 10uF cap should connect to R7.

I would try to experiment with just one circuit change at a time, especially since most people do not have a problem with their builds of this circuit.  I have successfully built the ET three times in the past (versions 1,2 and 4) and never had a problem (except for the version 4 which had a minor problem if an LM13600 was used instead of a LM13700 due to how the output buffers work).

Quote from: DrAlx on June 08, 2022, 01:26:32 PM

Quote from: matopotato on June 08, 2022, 10:22:02 AM
If I first measure voltage on the OTA connecting pin and then the other side of 10k, and set minus of 10uF to the lower potential, the is "safe"?

Correct. I would try that capacitor change on its own, leaving the resistor at a value of 10k.
EDIT:  If the voltages written on the circuit diagram are correct, the + side of the 10uF cap should connect to the opamp output, and the - side of the 10uF cap should connect to R7.

I would try to experiment with just one circuit change at a time, especially since most people do not have a problem with their builds of this circuit.  I have successfully built the ET three times in the past (versions 1,2 and 4) and never had a problem (except for the version 4 which had a minor problem if an LM13600 was used instead of a LM13700 due to how the output buffers work).

Thanks.
Yes, I have the same reflection.
I tried the 47k parallel, no change
And 10uF in series. It was 4.6 something at the junction with 220R, and 5.7 something on the other end, so I put minus closest to the OTA. No change.
Took a leap of fait and swapped, no change.
Sorry.

A reflection: I have been trying so many things by now, and lately it got all bassy and muddled on me. Some less distortion. Seems the breadboarding is coming apart from all the tearing and swapping. Might have to redo that.
After some re-grounded pins I had forgotten left out, it got back to its "normal" scrape-distortiony self.
In the trial I sometimes forgot to disconnect etc, and I notice that I can remove or cut off several things and there is no change to the distortion.
So rebuild might be in order.

Quote from: merlinb on June 08, 2022, 11:00:10 AM
Write the voltages on the circuit diagram
You have given us conflicting voltages on the same wire. How can IC1 pins 6 & 7 give different readings when they are shorted?
IC2 pins 6 & 7 are way low, they should be at Vref or higher when idle. Either IC2 pins are connected wrong or something in the side chain is incorrect (backward diode?).
(https://i.postimg.cc/23Y0wmTV/2022-06-02-21-06-44-Thumb-Sucker.jpg) (https://postimg.cc/23Y0wmTV)

(https://i.postimg.cc/QH3WxHzS/2022-06-08-20-40-00-Fuzz-Bender-DIY-does-no-fuzz-or-sound.png) (https://postimg.cc/QH3WxHzS)

There is no reason to shout. I can still read....
I can understand you are frustrated that some of us posting here do not follow praxis. And as per the picture above I was told in another thread to post it the way I have in my two reading sessions in this thread. Which leads me to think that there are more than one ways to present readings.
So sorry about that, I was following what I thought was the norm.

Yes, how can they give different values on pins 6 and 7. I took a DMM and place the red one on pin 6, read it, then pin 7 read it while have black to a common ground. I wrote it down.
I realize I shouldn't have. I should have gone on until they were the same. Until reality decided to confine to theory. But I thought "That's odd, but I will not judge at this point. If I am asked to re-measure I will".
But Now I think I should re-breadboard it first.
And then I can re-measure. And present in two ways for the greater benefit, one on the schema and one in table.

Quote from: Kevin Mitchell on June 08, 2022, 11:32:22 AM
Conflicting voltages or unstable power supply?
Hmmm....

I don't know. I use a Truetone 1 Spot CS12 or CS6. And I feel it has been stable. Then I have used the wall wart I got from some pedal purchase in some cases, one from EHS and another small I think from Source Audio.
Is it strange? Yes.
I will rebuild and then re-measure again. And hope to be brave enough to present whatever readings I get.
Got me thinking of
"...then whatever remains, however improbable, must be the truth"
But if all this gets to "said and done" most likely there is some error on my side.

Quote from: duck_arse on June 08, 2022, 12:03:38 PM

QuoteIC2 got some variations, this was the latest read
4,30  8,84
4,46  2,69
4,0    2,02
0       --- falling

pin 5 falling would indicate the rectifier had input signal applied. 2V69 at pin 7 would mean "compressing". but not while you have 4 something volts that should be coming from pin 1. I think.

Thanks. I take this as another vote for "Re-build. Re-measure" (Title of a Roxy Music album that never got released...)
I hope you liked the pictures though, despite amateur quality shots.

Quote from: merlinb on June 08, 2022, 11:00:10 AM
Write the voltages on the circuit diagram
You have given us conflicting voltages on the same wire. How can IC1 pins 6 & 7 give different readings when they are shorted?
IC2 pins 6 & 7 are way low, they should be at Vref or higher when idle. Either IC2 pins are connected wrong or something in the side chain is incorrect (backward diode?).
(https://i.postimg.cc/23Y0wmTV/2022-06-02-21-06-44-Thumb-Sucker.jpg) (https://postimg.cc/23Y0wmTV)

(I still appreciate that you respond. Thanks)

Quote from: matopotato on June 08, 2022, 02:55:14 PM

Quote from: Kevin Mitchell on June 08, 2022, 11:32:22 AM
Conflicting voltages or unstable power supply?
Hmmm....

I don't know. I use a Truetone 1 Spot CS12 or CS6. And I feel it has been stable. Then I have used the wall wart I got from some pedal purchase in some cases, one from EHS and another small I think from Source Audio.
Is it strange? Yes.
I will rebuild and then re-measure again. And hope to be brave enough to present whatever readings I get.
Got me thinking of
"...then whatever remains, however improbable, must be the truth"
But if all this gets to "said and done" most likely there is some error on my side.

When I see things like this the first thing I try is pull all ICs to see if the power supply stabilizes.
Then install IC1, check VR and the main supply again...
Continue forward until you find a possible problematic IC that's mucking things up.
Otherwise, you've got a noisy supply and probably shouldn't be dismissed.

But I could very well be drawing your attention further from *the real problem*.

I'm kind of itching to hop on the ET Comp train. Breadboard it again to try and help solve some of these riddles...
It's been years and I'm pretty sure it failed using a CA3080 - either error on my part or I too suffered the same result as few others. Sadly the success of others had me dismiss it as user error or a naughty breadboard.
I can put up some oscilloscope shots if it's of any use.

I downloaded a bit of motopotato's soundcloud file and opened it in audacity to see what the distortion looked like.
The picture is cut from about 13 seconds into the original recording where a note was dying down yet there was still buzz distortion on it.
I notice two things:

1) The buzz sound comes from a high frequency ripple on the wave form.
2) That ripple is mostly on the bottom part of the waveform. e.g. 0.007s , 0.027s, 0.047s  etc

To me, it doesn't suggest an op-amp limit is being reached.
It does suggest there is some sort of asymmetry at play.

(https://i.ibb.co/LPHL6sH/ET-distortion.png)

Thanks DrAlx, really cool. Unfortunately that distortion is now definitely like a fuzz right now.

So I re-boarded it. That is went through each connection to verify connectivity.
Then I tested. after a tip, to use the other unused "Side" of the LM13700. I got the pinout so I could separate the buffer from the rest. Kept the buffer connected "as is" and for the other connectors I switched sides. There was no difference to the problem though.

I then went on to measure. Some parts stay stable, others keep rising or falling. And when I get around to the PNP, the pins 6 and 7 on the IC2.2 have moved again in values, so my values do not quite make sense. I tried at one stage to wait it out. And when I thought it settled, went to other places, got back and it had snuck up again, only to fall when I measure.
So "what are the voltages"? Well, when do you want to know? Feels really odd.
Anyway, I try to be a good bot and measure anyway and paste in the schema.
I had signal chain connected, strummed once in a while, but that did not seem to affect the readings.
I could try with only the DC power connected and see if that makes it more stable or not.

I'm wondering if the fluctuations and instability could be part of the problem...
I had background noise a while until I found a cable that had jumped. Even with my ignorance I felt the values had been off, and then measured again. Some went better, but IC2 fluctuate a lot.
IC1 is quite stable but pins 6&7 vary slightly.
PNP takes a beating from IC2 I suppose, or they tease each other. The LM13700 seems the more stable one at this point.


(https://i.postimg.cc/BLFNDczL/Thumb-Sucker-Schema-Copy1.png) (https://postimg.cc/BLFNDczL)

Quote from: matopotato on June 08, 2022, 02:49:25 PM........leads me to think that there are more than one ways to present readings......

This struggle has gone on for a week in multiple threads. What you are doing clearly is not working.

The idea that you can modify or rip-up your breadboard is very distressing. If you can not trust your connections, take-up another hobby.

You did take Merlin's advice. A very funny thing stands out on schematic rather than as text list.
(https://i.postimg.cc/phNnqVHX/noreasontoshout-42.gif) (https://postimg.cc/phNnqVHX)

HTH can you have 4V one stage and 2V another stage? Yes, we could design it that way, and there are some 0.6V drops, but a little 1k resistor with an "infinite" (TL072) load will not lose voltage like that.

Busted pot wires? (K.I.S.S.: Wire fixed resistors until it works good.)

Shorted caps? (Normally you can remove caps and not affect DC levels, but this may be an exception.)

Bad chips? Stray wire scraps? Termites?

Quote from: matopotato on June 08, 2022, 06:01:35 PM...So I re-boarded it. That is went through each connection to verify connectivity.

Thanks: but now you have "impossible" readings.

I marked some arrows in Red- these pairs of points are on the SAME wire and would have to be equal. Why aren't they?

The Base-Emitter voltage can only be zero to <1V. When working happy (this may not work at idle) we expect 0.6V. Not 2.1V. Bad transistor? Wrong transistor? Mistaken pinout? A breadboard so goofy that the two ends of the wire IC2.2 to Q1 change connection moment to moment?
(https://i.postimg.cc/LJDpxxFq/noreasontoshout-B-42.gif) (https://postimg.cc/LJDpxxFq)

Quote from: Kevin Mitchell on June 08, 2022, 04:58:21 PM

Quote from: matopotato on June 08, 2022, 02:55:14 PM

Quote from: Kevin Mitchell on June 08, 2022, 11:32:22 AM
Conflicting voltages or unstable power supply?
Hmmm....

I don't know. I use a Truetone 1 Spot CS12 or CS6. And I feel it has been stable. Then I have used the wall wart I got from some pedal purchase in some cases, one from EHS and another small I think from Source Audio.
Is it strange? Yes.
I will rebuild and then re-measure again. And hope to be brave enough to present whatever readings I get.
Got me thinking of
"...then whatever remains, however improbable, must be the truth"
But if all this gets to "said and done" most likely there is some error on my side.

When I see things like this the first thing I try is pull all ICs to see if the power supply stabilizes.
Then install IC1, check VR and the main supply again...
Continue forward until you find a possible problematic IC that's mucking things up.
Otherwise, you've got a noisy supply and probably shouldn't be dismissed.

But I could very well be drawing your attention further from *the real problem*.

I'm kind of itching to hop on the ET Comp train. Breadboard it again to try and help solve some of these riddles...
It's been years and I'm pretty sure it failed using a CA3080 - either error on my part or I too suffered the same result as few others. Sadly the success of others had me dismiss it as user error or a naughty breadboard.
I can put up some oscilloscope shots if it's of any use.

I think IC1 is central for Vref at least. And VCC is stable at 9.29 this time. And they have been in and out earlier during swap testing with a third TL072. So put that in the mix and rotated around. No change.
The supply has not been an issue in other cases, and I used 3 different ones. Home appliances have not complained either so the base power in the house feels ok.
I appreciate the "make sure you start from the right base and work yourself up" well, forward perhaps. And I subscribe to it in many troubleshooting scenarios, but I honestly feel I have no reason to distrust my power supply.

About the ET in general. I wish I had more example experiences to compare with. The circuit and its implementations get overall very high praise, so I too think it is something I've done wrong. Or perhaps my first case of faulty component.
Because others have them working fine. OK some extreme settings might cause a little bit of distortion, but I think that is understood and expected. And using all extremes or some specific "bad" settings can cause the circuit to chase itself I think I read somewhere.
But having now two copies. Swapped everything else around, tested two different LM13700's (but only in the build though) I can no longer see any part or component that if identified would make me go "Yes, of course, now it makes sense and fits together" because I feel I have changed everything.
Unless it is some evil component conspiracy where several individuals in combination take turns causing the problem. But then the probability is at zero IMHO.

Might try another round of measures again tomorrow. Perhaps another sound sample since it now sounds really bad.
Unless anyone is interested in a Dying Battery Fuzz with Random Bypass. 5 knob version.

Quote from: PRR on June 08, 2022, 06:13:43 PM

Quote from: matopotato on June 08, 2022, 06:01:35 PM...So I re-boarded it. That is went through each connection to verify connectivity.

Thanks: but now you have "impossible" readings.

I marked some arrows in Red- these pairs of points are on the SAME wire and would have to be equal. Why aren't they?

The Base-Emitter voltage can only be zero to <1V. When working happy (this may not work at idle) we expect 0.6V. Not 2.1V. Bad transistor? Wrong transistor? Mistaken pinout? A breadboard so goofy that the two ends of the wire IC2.2 to Q1 change connection moment to moment?
(https://i.postimg.cc/LJDpxxFq/noreasontoshout-B-42.gif) (https://postimg.cc/LJDpxxFq)

Yes, I know they are impossible readings.
I tried to say that some keep varying. How long to wait? Until they reach zero? When are they to be regarded as stable?
I measure, come back for other reason like you mention impossible values and they have changed.
I don't think I have fried the DMM (yet).

So I could make up values to calm things down, but that would be counterproductive and useless.
I feel that I am the messenger rather than the message.
Yes, I should probably take up some other hobby. Leave you guys to it and stop disturbing this forum. Last thing I want is to be regarded as a negative guy causing distress.
But effects, pedals is my passion too. Sorry, can't really help it. It has only been a year since I started with this and I feel I am learning, but far from know it all yet. (Probably never will).
I also have a strong drive on troubleshooting, logic and "customer focus" from other walks in my life.
And I felt that my pedal problem would be "solvable" with some help. Especially since two other members had the same or very similar problem.
But now it seems to be more of a nuisance than of interest.

Quote from: matopotato on June 08, 2022, 06:29:30 PM
But now it seems to be more of a nuisance than of interest.

What ? PRR is only trying to help, with is own original style. I am following this thread with great interest !

The fact that there are four active threads about the Engineer's Thumb  is easily and perfectly understandable :

There's an old one,with a similar issue from reply #31, with some possible leads.

There are three Engineer's Thumb builds that don't work correctly.

I even suspect there are more builds showing the exact same issue, and their users don't know there is something wrong with their compressor... I suspect it because I was one of them...see reply #2. We are most probably doing something that will be useful for the next builds.

I am sure Merlin the Valve Wizard is proud of his compressor, and happy to see people struggling to make them work, instead of throwing them away without a second thought.

So thank you Matopotato for bringing this distortion issue to my attention.

Without you and Wook22, I would have thought this compressor was quite weak and easily distorting the signal. I am no engineer or scientist, I studied letters, foreign languages, and I started building circuits because I play music. I didn't suspect there was an issue with my build... I built it carefully, just like I did with 40 or 50 stompbox kits before, and I can't find any obvious issue, at least not on my own.

So far you have been really contributing, at least from my point of view.

...please take it easy...breath...where is your "jacket" ? Think about the Common Good... we may get to the bottom of it...hopefully.

Another theoretical thought try from my side, before starting to breadboard this circuit:
what happens to the "fuzz", when the inverting OTA-input (pin4) is not directly connected to Vref (4.5V) as in the original schemo, but through a 220R resistor?
(before trying a 500R trimpot pot across the +/- inputs with wiper to Vref, as another possibility to check whether the whole case is an offset-/symmetry-issue; or even AC-coupling the OTA).

Quote from: matopotato on June 08, 2022, 06:29:30 PM
Yes, I should probably take up some other hobby. Leave you guys to it and stop disturbing this forum. Last thing I want is to be regarded as a negative guy causing distress.
But now it seems to be more of a nuisance than of interest.

no. your prose style is too interesting, you'd better stick at it.


I had a go at the rectifier section on the breadboard today, cause I wasn't sure about what to expect. now, I can honestly say I have no idea what or how it is doing, but do know what to expect. about your measures - there is a process.

no audio, no looper, no signal in, not to start with. build the thing on the breadboard, neatness counts. we even like photos of that stage, just to make sure of things you tell us. [and yes, thanks for the pics.] build the circuit, power on, measure all the voltages. just measure them and write them down - if you have to wait for a moving voltage when there is no input signal [which is rule number one, just quoted], then the voltage [or the measure method] is wrong.

if you have a full build doc with a complete circuit diagram with all IC references and pin numbers included on same, [and your breadboard follows same exactly] then yes, text form voltage postings is fine, because you will obviously have included all those critical docs in the first post of the thread. and - writing the voltages on the circuit is a useful diagnostic tool, as we have seen.

my partial breader showed that there should be half supply volts on all the IC2 pins [on your pedalpcb circuit] from the thresh pot wiper thru to the transistor base pin. give or take a few hundred millivolts, but nothing less than 4V. I also found that when I whacked it with signal, those voltages didn't move by more than 100mV at the R9//C5 point, and it went down.

but that did make the transistor do stuff, pass current into a resistor as load which varied with the input signal level, so I call that a success.

stick at it.

This is probably nothing but I 'd like to make sure...

According to PedalPCB values (your R10 corresponds to my R11 and vice-versa),

Do you have continuity between both R11 (1M) pads and E, B and C (BC327) ?

I also have continuity between D4- , one R11 pad and both R10 pads (still with PPCB nomenclature).

According to our schematics, I wouldn't expect that, is it the same on your build ?

Quote from: matopotato on June 08, 2022, 06:29:30 PM.....effects, pedals is my passion...

So get passionate about figuring why your build and readings are not making sense.

I'm just pointing out places _I_ think you should be looking. Don't take it as criticism.

Quote from: eh la bas ma on June 09, 2022, 02:26:21 PM
This is probably nothing but I 'd like to make sure...

According to PedalPCB values (your R10 corresponds to my R11 and vice-versa),

Do you have continuity between both R11 (1M) pads and E, B and C (BC327) ?

I also have continuity between D4- , one R11 pad and both R10 pads (still with PPCB nomenclature).

According to our schematics, I wouldn't expect that, is it the same on your build ?

I am a bit puzzled now...  When the power jack is inserted, I have theses strange connections as described above, but not when the 9V power jack is unplugged...then I have continuity as shown on schematics...

Edit : I thought I was dreaming or something, so I reflowed the pads in this aera, looked for shorts, but still...
Same behavior with sockets once I took off the transistor.

Edit 2 : I might need to borrow your straitjacket... is it available ?

Sorry. Life and work happend. Will buy components, and do measurements, and photos during weekend.

Quote from: matopotato on June 09, 2022, 04:00:03 PM
Life and work happend.

Reality is so damn thoughtless like that! Doesn't it realise I have more important stuff to do?!?  :icon_biggrin:

I managed to get another B1M pot plus some trimmers. I will try the trimmer suggestions tomorrow I hope @puretube.
For what it is worth, the PCB build I restored and it sounds as at the outset. Distorts much "sooner" than my friend's ET. His only begins to distort a little with Ratio full CW and Threshold full CCW. As I have understood this is normal behavior considering how the parts interact, so no issue there. When he rolls on a little bit of threshold the noise is gone.
In my case at 3 and 9 respectively, it is still there, even at noon. Of course guitar volume, pedal volume, pickups etc influence this, but the distortion/scrapy sound is remarkably consistent on my Thumb Sucker PCB version.
The breadboard now has all its onw parts except the ICs and PNP. And it distorts quite a bit worse, like a dying battery fuzz at times. But it did sound the same as the PCB build at the outset, so it should be possible to use as experimentation.

I measured both and found IC2, pin1 on breadboard to be 0.0V. So I swapped out the D1, D2 and D5 (for good measure) to fresh 1N4148's. But still the same.
Also the breadboard circuit showed a lot more fluctuations, mostly rising values. I marked with * the ones that kept changing. So forgive me if they come out impossible. E.g. IC2 pin7 and PNP Base went from 5.70-ish to 7.60. In tandem though, so they did learn a lesson from last. I could they were afraid I would tell them off, but rising they went.

No cables, In or Out from guitar or any other signal were involved during the measurements.

Anyway, here are the readings:
Breadboard, Graphical:
NB: I missed the 4.79 on IC3 pin4. It is included properly below though. In the txt version

(https://i.postimg.cc/4HPz8SCM/2022-06-10-22-45-Thumb-Sucker-Schema-BBD.png) (https://postimg.cc/4HPz8SCM)

Breadboard, txt:

Power in 9.84
VCC 9.62 - 9.60

IC1
4.60   9.61
4.79   4.80
4.37   4.80
0.00   4.76

IC2
0.00   9.62
4.80   5.80-7.60
4.69   6.75 (at some point)
0.00   4.72

PNP
C 1.10
B 5.70-7.60
E 6.78 (at some point when B was high)

IC3
1.10   0.00
0.55   0.00
4.59   0.00
4.79   0.00
4.79   0.00
0.00   9.60
0.00   0.00
0.00   0.00


PCB build
Graphical. Again * is for fluctuating values I think all were on the rise.

(https://i.postimg.cc/302K7srS/2022-06-10-22-55-Thumb-Sucker-Schema-PCB.png) (https://postimg.cc/302K7srS)

PCB Build, txt:

Power in 9.85
VCC 9.65

IC1
5.00   9.64
4.84   4.70*
4.41   4.81*
0.00   4.70*

IC2
4.76   9.64
4.82   4.33
4.77   4.82
0.00   4.67

PNP
C 1.12
B 4.32
E 4.82

IC3
1.12   0.00
0.20   0.00
4.82   0.00
4.82   0.00*
4.83   0.00*
0.00   9.64
0.00   0.00
0.00   0.00


Some uninitiated observations: The PBC looks better, more stable values and seem to be "better", but the original problem is still present very much. I don't see this a pedal I would give to anyone else as a compressor, let alone charge money for it.

Why the breadboard (re-continuity checked again today) sounds much worse is also a mystery. Might have to rebuild it from scratch to have both on par to test some of the remaining suggestions.

@duck_arse: Here is the breadboard, but it is not for the faint-hearted.
I tried to translate "neatness" to Swedish, but google gave up on me, so... I'm gonna guess "amount"...


(https://i.postimg.cc/yJNcdPZX/20220610-221629.jpg) (https://postimg.cc/yJNcdPZX)

(https://i.postimg.cc/GBN8p1rd/20220610-221636.jpg) (https://postimg.cc/GBN8p1rd)

(https://i.postimg.cc/479K7FNt/20220610-221638.jpg) (https://postimg.cc/479K7FNt)

(https://i.postimg.cc/YLBv1fhP/20220610-221641.jpg) (https://postimg.cc/YLBv1fhP)

(https://i.postimg.cc/t17ny4KB/20220610-221644.jpg) (https://postimg.cc/t17ny4KB)

(https://i.postimg.cc/Mn9fhQFc/20220610-221646.jpg) (https://postimg.cc/Mn9fhQFc)

Quote from: eh la bas ma on June 09, 2022, 02:42:10 PM

Quote from: eh la bas ma on June 09, 2022, 02:26:21 PM
This is probably nothing but I 'd like to make sure...

According to PedalPCB values (your R10 corresponds to my R11 and vice-versa),

Do you have continuity between both R11 (1M) pads and E, B and C (BC327) ?

I also have continuity between D4- , one R11 pad and both R10 pads (still with PPCB nomenclature).

According to our schematics, I wouldn't expect that, is it the same on your build ?

I am a bit puzzled now...  When the power jack is inserted, I have theses strange connections as described above, but not when the 9V power jack is unplugged...then I have continuity as shown on schematics...

Edit : I thought I was dreaming or something, so I reflowed the pads in this aera, looked for shorts, but still...
Same behavior with sockets once I took off the transistor.

Edit 2 : I might need to borrow your straitjacket... is it available ?

Just for completeness and the digital archeologists: It was sorted in this thread https://www.diystompboxes.com/smfforum/index.php?topic=129237.20 (https://www.diystompboxes.com/smfforum/index.php?topic=129237.20) that measuring continuity and other stuff while pushing signal through can cause unexpected effects.

Mi Straightjacket, Tu Straightjacket. I think it is 9XXXL so it will fit us both. You can even stay in France and me in Sweden I think. There is room for everyone.

Quote from: puretube on June 09, 2022, 04:40:42 AM
Another theoretical thought try from my side, before starting to breadboard this circuit:
what happens to the "fuzz", when the inverting OTA-input (pin4) is not directly connected to Vref (4.5V) as in the original schemo, but through a 220R resistor?
(before trying a 500R trimpot pot across the +/- inputs with wiper to Vref, as another possibility to check whether the whole case is an offset-/symmetry-issue; or even AC-coupling the OTA).

I plan to try this tomorrow.
I like the idea of the signal being offset as a possible source for problems. When I used a scope a few weeks back it seemed that when dialing up so the problem appeared, it first showed as a flat top on the tonegenerator wave, but the bottom was fine and sinus-y. Until I pushed harder of course. And if there is an offset issue, that can be softened or pushed further down the line so to speak, then that might be enough to keep the good sound until you hit the extremes, where it distorts anyway and also is sort of bad territory. At least it would make sense IMHO. And if I ever sort this out I think I would like to understand what was the cause.

Priority should be to get voltages that make sense.

If you did a lot of trials, unsoldering then soldering parts back on the board, etc. it wouldn't be very surprising that there are some scraps, some remains of solder on the soldering side.

You might want to clean everything with your iron and a dry toothbrush, reflow all suspicious pads (and those that look good), hunt for shorts, perform a ritual sacrifice to the diy goddess (while listening to The Bloods), and then try to check those voltages. Finally compare them with your friend's compressor (give him your blueshift, he will agree i am sure). See if anything stands out. (Edit : remember IC and transistors are heat-sensitive, remove them if you clean the board with your iron)

Duck_Arse helped me verify if the sidechain was working on my build. There are three points of interest :
(https://i.postimg.cc/ZvrwM1yT/Screenshot-2022-06-11-at-01-35-29-Thumb-Sucker-Thumb-Sucker-Pedal-PCB-pdf.png) (https://postimg.cc/ZvrwM1yT)

Blue circle is C3/R9 junction,  Voltage here should be sensitive to the Release control. If you turn it, the voltage in the blue circle changes.

Red circle on your schematics corresponds to pin 10 of the TL74 on my board, for you it's IC2 pin 5. Voltage here should follow the value at C3/R9 junction.

Finally green circle :

Quote from: eh la bas ma on June 09, 2022, 01:20:01 PM

Quote from: duck_arse on June 09, 2022, 11:15:27 AM

but that did make the transistor do stuff, pass current into a resistor as load which varied with the input signal level, so I call that a success.

stick at it.

I notice something happens At R10/BC237 junction when I strum.

Ratio = 2'  Threshold = 9' Attack= 9' Release= 12' -->> 1.118 V. switching on : 1.117 V and if i strum it goes up to 1.268 V and goes down gradually to 1.117 V

Does it do the same on your build ? Measure voltage in the green circle first with no signal, then try again while strumming your guitar (no looper, a real guitar, full volume). Circuit powered and switched on.

Quote from: eh la bas ma on June 10, 2022, 07:45:27 PM
Priority should be to get voltages that make sense.

If you did a lot of trials, unsoldering then soldering parts back on the board, etc. it wouldn't be very surprising that there are some scraps, some remains of solder on the soldering side.

You might want to clean everything with your iron and a dry toothbrush, reflow all suspicious pads (and those that look good), hunt for shorts, perform a ritual sacrifice to the diy goddess (while listening to The Bloods), and then try to check those voltages. Finally compare them with your friend's compressor (give him your blueshift, he will agree i am sure). See if anything stands out. (Edit : remember IC and transistors are heat-sensitive, remove them if you clean the board with your iron)

Duck_Arse helped me verify if the sidechain was working on my build. There are three points of interest :
(https://i.postimg.cc/ZvrwM1yT/Screenshot-2022-06-11-at-01-35-29-Thumb-Sucker-Thumb-Sucker-Pedal-PCB-pdf.png) (https://postimg.cc/ZvrwM1yT)

Blue circle is C3/R9 junction,  Voltage here should be sensitive to the Release control. If you turn it, the voltage in the blue circle changes.

Red circle on your schematics corresponds to pin 10 of the TL74 on my board, for you it's IC2 pin 5. Voltage here should follow the value at C3/R9 junction.

Finally green circle :

Quote from: eh la bas ma on June 09, 2022, 01:20:01 PM

Quote from: duck_arse on June 09, 2022, 11:15:27 AM

but that did make the transistor do stuff, pass current into a resistor as load which varied with the input signal level, so I call that a success.

stick at it.

I notice something happens At R10/BC237 junction when I strum.

Ratio = 2'  Threshold = 9' Attack= 9' Release= 12' -->> 1.118 V. switching on : 1.117 V and if i strum it goes up to 1.268 V and goes down gradually to 1.117 V

Does it do the same on your build ? Measure voltage in the green circle first with no signal, then try again while strumming your guitar (no looper, a real guitar, full volume). Circuit powered and switched on.

Thanks. Will add to list of tests for sure.
Actually the pcb board is the one behaving best and more consistent during my trials and despite changing things on it, it still is as from the outset.
The breadboard vetsion is a different beast though.
Plan is to build up again on a new breadboard. This one can be a bit wobbly in some holes.
Then
try @puretube suggestions around signal offset adjustments.
Then go through the test from above.
What did it make you find or discover or adjust?

I re-breadboarded the circuit on a new breadboard. Looked up the neatness and got luckier. Tried to adjust accordingly.
Same distortion. It is more on the Breadboard version than the PCB still. If I touch with finger on some of the pots, there is a change to the noise, but the distortion mainly remains the same. It is less on treble strings, and more on bass. And quite full on chord strumming. Which is consistent with my findings since day 1.
Tried two wall warts and battery. No differences I could detect. Stayed with the 9.0 stamped wart in the end.

Readings BBD V2:

(https://i.postimg.cc/XpB17Gyr/2022-06-11-14-17-Thumb-Sucker-Schema-BBDv2.png) (https://postimg.cc/XpB17Gyr)

Breadboard, txt:

Power in 9.17 (Got a b
VCC 8.92

IC1
4.57   8.91
4.48   4.46
4.03   4.47
0.00   4.29

IC2
4.59   8.91
4.41   4.77
4.37   4.46
0.00   4.37

PNP
C 1.10
B 4.76
E 4.46

IC3
1.10   0.00
0.18   0.66-0.06*
4.47   0.50-0.01*
4.46   0.67-0.06*
4.48   0.70-0.06*
0.00   8.91
0.00   0.00
0.00   0.00

* These were falling values. And that side is not even used, so probably non-interesting. But I added them just in case.

Will try the trimmers as @puretube suggested later on.
Will try the RGB @duck_arse points with signal from guitar.
I have a generator and an old 1-ch scope in case there is something useful I should try with them?

Quote from: eh la bas ma on June 10, 2022, 07:45:27 PM
... Finally compare them with your friend's compressor (give him your blueshift, he will agree i am sure). See if anything stands out.

Yes, might come to that. Actually he had a TC E 3rd Dimension (BOSS DC-2 sort of) that is his least liked pedal. So I have it to compare with Blueshift. Sadly Blueshift hasn't sung yet and I owe you the IC swap change. All prepped, but I figured better to concentrate on one brick at a time.
I got as far as noticing the upper deck first IC didn't have proper power so I suspect the power stage, bad solder. I am more hopeful once I can get readings for all ICs that it will actually perform. But that is another thread.

Quote from: matopotato on June 11, 2022, 03:56:32 AM
What did it make you find or discover or adjust?

That the sidechain was working on my build.

I didn't change anything. I tried to modify the input resistor, as suggested by a skilled forumite, from 1k to 10k. It didn't change anything obvious, so i soldered the 1k back on my board. I remembered Merlin said :

Quote from: merlinb on December 19, 2020, 06:10:50 AM
The circuit works with the component values in the schematic, changing them isn't going to fix anything, it's more likely to create new problems.

Edit: I notice your last readings are very similar to mine, as you can see in my thread, reply #8. I'd say they're allright, they "make sense" ?

neatness - tidy, ordered, sensible, all squared, no wobbly long legged resistors hanging about. and those ground links! short, straight, bare copper wire formed like a staple [stationery] is best, makes sense, non-confusable, not those long looping black wires you show.

and that diode with the red and white paper ----- remove the paper bandoliers, they have and leave problem glue gunk. ANY/ALL parts with that gunk on their leads ends, cut the ends off. never ever shove one into the breadboard, it will only end in straitjacket.

as for your latest voltages, they are looking right, sensible, as EHLB sez. however, ignore what I said about the C5 and C6 points voltages moving with signal - I found they stayed steady, as near as, but the transistor collector voltage did move in sympathy with signal level. you need to be careful measuring this point on your IC, as you can fritz the chip if you slip with a probe.

and as for you mate's box pot positions comparison - if his pots are a different taper to yours, or even a different manufacturor, you are comparing your oranges to his apples, your knob settings won't match.

Quote from: duck_arse on June 11, 2022, 10:18:01 AM
neatness - tidy, ordered, sensible, all squared, no wobbly long legged resistors hanging about. and those ground links! short, straight, bare copper wire formed like a staple [stationery] is best, makes sense, non-confusable, not those long looping black wires you show.

and that diode with the red and white paper ----- remove the paper bandoliers, they have and leave problem glue gunk. ANY/ALL parts with that gunk on their leads ends, cut the ends off. never ever shove one into the breadboard, it will only end in straitjacket.

as for your latest voltages, they are looking right, sensible, as EHLB sez. however, ignore what I said about the C5 and C6 points voltages moving with signal - I found they stayed steady, as near as, but the transistor collector voltage did move in sympathy with signal level. you need to be careful measuring this point on your IC, as you can fritz the chip if you slip with a probe.

and as for you mate's box pot positions comparison - if his pots are a different taper to yours, or even a different manufacturor, you are comparing your oranges to his apples, your knob settings won't match.

Thanks a lot.
Still have some learning to digest. I tend to keep legs and paper until they go to be soldered on a pcb or perf/vero/strip board. But point taken.

Will use wire and crocodile clip instead of probe then.

Pot from same place and will check values.
I also hade my Thumb Sucker kit compared with other builders if the same regarding pot settings. And my problem was confirmed. My friends ET is as close to hands on as I can get.

EDIT: Yes, 2 pots differ at least

Quote from: puretube on June 09, 2022, 04:40:42 AM
Another theoretical thought try from my side, before starting to breadboard this circuit:
what happens to the "fuzz", when the inverting OTA-input (pin4) is not directly connected to Vref (4.5V) as in the original schemo, but through a 220R resistor?
(before trying a 500R trimpot pot across the +/- inputs with wiper to Vref, as another possibility to check whether the whole case is an offset-/symmetry-issue; or even AC-coupling the OTA).

I was not sure how to connect the 500R trimmer. I tried 220R from pin4 before going to Vref, but no change.
I think you mean to put the 500R between pin3 and 4.. As a bridge? and leave all other connections as they are?

For a moment the breadboard worked the same as the PCB. That is not fuzzy, but with distortion if I take Ratio a bit over noon and Threshold below noon. At my "would like it to sound clean at least here" with R at 3 and T at 9 there is still distortion.
So the Breadboard works just as "well" as the PCB now. ("Ett fall framåt"-A fall forward)
Then I tried some tips to make the OTA offset adjustable, hopefully to some more central point as suggested by @puretube. And I think I did not quite made the connections properly, so will have to re-think/re-ask about more detail. So I put things back, and the distortion had gotten worse again.
So there is something loose and I am touching on the breadboard mocking things up for sure.
Still the breadboard has the capability to act as the PCB does, so I should be able to experiment on it and try things out. If I can get back to the somewhat less distortion mode, then I can evaluate for sure. Else I can probably evaluate maybe some stuff, but it might be a false approach in case some error would hide the solution to another.
Would like to at least try the wiper idea in case the signal is offset. But should try to get back to a more stable circuit first.

Quote from: matopotato on June 11, 2022, 05:25:36 PM

Quote from: puretube on June 09, 2022, 04:40:42 AM
Another theoretical thought try from my side, before starting to breadboard this circuit:
what happens to the "fuzz", when the inverting OTA-input (pin4) is not directly connected to Vref (4.5V) as in the original schemo, but through a 220R resistor?
(before trying a 500R trimpot pot across the +/- inputs with wiper to Vref, as another possibility to check whether the whole case is an offset-/symmetry-issue; or even AC-coupling the OTA).

I was not sure how to connect the 500R trimmer. I tried 220R from pin4 before going to Vref, but no change.
I think you mean to put the 500R between pin3 and 4.. As a bridge? and leave all other connections as they are?

One end of the pot to pin 3, the opposite end to pin 4, and the wiper to Vref (4.5V).
Lift the end of the 220ohm resistor that goes from pin 3 to Vref (in the orig. schematic) on the Vref-side and leave it floating, while testing the trimpot-settings.

Quote from: puretube on June 12, 2022, 05:16:47 AM

Quote from: matopotato on June 11, 2022, 05:25:36 PM

Quote from: puretube on June 09, 2022, 04:40:42 AM
Another theoretical thought try from my side, before starting to breadboard this circuit:
what happens to the "fuzz", when the inverting OTA-input (pin4) is not directly connected to Vref (4.5V) as in the original schemo, but through a 220R resistor?
(before trying a 500R trimpot pot across the +/- inputs with wiper to Vref, as another possibility to check whether the whole case is an offset-/symmetry-issue; or even AC-coupling the OTA).

I was not sure how to connect the 500R trimmer. I tried 220R from pin4 before going to Vref, but no change.
I think you mean to put the 500R between pin3 and 4.. As a bridge? and leave all other connections as they are?

One end of the pot to pin 3, the opposite end to pin 4, and the wiper to Vref (4.5V).
Lift the end of the 220ohm resistor that goes from pin 3 to Vref (in the orig. schematic) on the Vref-side and leave it floating, while testing the trimpot-settings.

Thanks. Took a little bit for me to get it right. And it "works" in the sense that it affects the distortion.
CCW less distortion, less volume and mor of the oversaturated?, dying battery fuzz sound, gating?. To CW it gets back to more of its usual self with distortion but more volume and a bit clearer tone. I would like to check with the scope if I can recreate the flattened tops but round troughs.
And then drive the trimmer to see if it does even out the curve. And if so, then try a 500R across pins on my pcb version and some eqviv R from the trim between pin3 and Vref.
So a bit more promising than other tests. Will travel next week so might be a while.

Quote from: duck_arse on June 11, 2022, 10:18:01 AM
neatness - tidy, ordered, sensible, all squared, no wobbly long legged resistors hanging about. and those ground links! short, straight, bare copper wire formed like a staple [stationery] is best, makes sense, non-confusable, not those long looping black wires you show.

and that diode with the red and white paper ----- remove the paper bandoliers, they have and leave problem glue gunk. ANY/ALL parts with that gunk on their leads ends, cut the ends off. never ever shove one into the breadboard, it will only end in straitjacket.

(https://i.postimg.cc/V0cbfckZ/20220612-200036.jpg) (https://postimg.cc/V0cbfckZ)

Quote
as for your latest voltages, they are looking right, sensible, as EHLB sez. however, ignore what I said about the C5 and C6 points voltages moving with signal - I found they stayed steady, as near as, but the transistor collector voltage did move in sympathy with signal level. you need to be careful measuring this point on your IC, as you can fritz the chip if you slip with a probe.

OK

Quote
and as for you mate's box pot positions comparison - if his pots are a different taper to yours, or even a different manufacturor, you are comparing your oranges to his apples, your knob settings won't match.

Pot            EngThumb    ThumbSucker
Level         A10k            A10k
Attack       A100k           B100k
Ratio         A1M              A1M
Threshold  B1M              B1M
Release     B500k           B1M

So Release differs, but when testing I keep it quite low. An neither of us have felt much effect from Release nor Attack. In my case likely due to the finer points being overshadowed by the distortion problem. In his case, you can hear something, but neither of us is much of compression knowledgeable so might take some getting used to.
Attack is also set low in the tests so I doubt A vs B has much impact either.
The other three same, so even though I would have understood some differences, what we hear when tweaking knobs still makes my problem (and him not having one) quite obvious.
Might try to film knob tweaking while playing to make it more clear. But that will have to wait a little.

Quote from: puretube on June 12, 2022, 05:16:47 AM

Quote from: matopotato on June 11, 2022, 05:25:36 PM

Quote from: puretube on June 09, 2022, 04:40:42 AM
Lift the end of the 220ohm resistor that goes from pin 3 to Vref (in the orig. schematic) on the Vref-side and leave it floating, while testing the trimpot-settings.

I plan to try this on the pcb version. I think I  can carefully bend pin 3 and 4 out from the socket and try your idea. Only thing is how to lift the 200R between its end and vref. I don't want to cut. Any thoughts? Some parallel R would work in the opposite way...

Quote from: matopotato on June 17, 2022, 07:10:40 AM

Quote from: puretube on June 12, 2022, 05:16:47 AM

Quote from: matopotato on June 11, 2022, 05:25:36 PM

Quote from: puretube on June 09, 2022, 04:40:42 AM
Lift the end of the 220ohm resistor that goes from pin 3 to Vref (in the orig. schematic) on the Vref-side and leave it floating, while testing the trimpot-settings.

I plan to try this on the pcb version. I think I  can carefully bend pin 3 and 4 out from the socket and try your idea. Only thing is how to lift the 200R between its end and vref. I don't want to cut. Any thoughts? Some parallel R would work in the opposite way...

then take out the 220R completely? (same effect)

Quote from: puretube on June 17, 2022, 01:29:38 PM

Quote from: matopotato on June 17, 2022, 07:10:40 AM

Quote from: puretube on June 12, 2022, 05:16:47 AM

Quote from: matopotato on June 11, 2022, 05:25:36 PM

Quote from: puretube on June 09, 2022, 04:40:42 AM
Lift the end of the 220ohm resistor that goes from pin 3 to Vref (in the orig. schematic) on the Vref-side and leave it floating, while testing the trimpot-settings.

I plan to try this on the pcb version. I think I  can carefully bend pin 3 and 4 out from the socket and try your idea. Only thing is how to lift the 200R between its end and vref. I don't want to cut. Any thoughts? Some parallel R would work in the opposite way...

then take out the 220R completely? (same effect)

No, I mean on the soldered pcb.
I have a copy on breadboard which I  tried but the ground problem is worse there. So I want to try your idea on the soldered PCB bynlifting 3 and 4 pinnout fromnits socket. Then crocodiles and loose wire should be possible to join with the trimmer.
Which leaves the 220R. Soldered. I guess I  have to desolder on ts vref side

Quote from: matopotato on June 17, 2022, 04:25:12 PM

Quote from: puretube on June 17, 2022, 01:29:38 PM

Quote from: matopotato on June 17, 2022, 07:10:40 AM

Quote from: puretube on June 12, 2022, 05:16:47 AM

Quote from: matopotato on June 11, 2022, 05:25:36 PM

Quote from: puretube on June 09, 2022, 04:40:42 AM
Lift the end of the 220ohm resistor that goes from pin 3 to Vref (in the orig. schematic) on the Vref-side and leave it floating, while testing the trimpot-settings.

I plan to try this on the pcb version. I think I  can carefully bend pin 3 and 4 out from the socket and try your idea. Only thing is how to lift the 200R between its end and vref. I don't want to cut. Any thoughts? Some parallel R would work in the opposite way...

then take out the 220R completely? (same effect)

No, I mean on the soldered pcb.
I have a copy on breadboard which I  tried but the ground problem is worse there. So I want to try your idea on the soldered PCB bynlifting 3 and 4 pinnout fromnits socket. Then crocodiles and loose wire should be possible to join with the trimmer.
Which leaves the 220R. Soldered. I guess I  have to desolder on ts vref side

If pin3 is out of the socket, the 220R is not connected to it anymore. Okay. But that 10k resistor must connect to pin3!
Bending IC-pins (and later trying to bend them back ...) is a dangerous thing! They love to break off.

Thanks, point taken. Still, I am reaching the end of ideas. I have one from another thread that will be revealed in July. And yours.
After that, unless fixed, I am considering donating it to science. With just the root cause explained in return. ;)
We'll see.
For the bent legs I'll probably desolder the 220R one leg.

Today I tried the suggestion from @puretube with the trimmer on pins 3 and 4 of the LM13700 as described in earlier posts.
It looks messy, but as far as I could tell it was connected properly. I lifted the 220R. Bent legs 3 and 4 out and inserted wire as needed.
There was an effect, Low R/CCW made the tone/sound thinker/bassier and slightly louder. And the opposite the other way.
But the distortion is still there and not too subtle either. A bit more difficult to turn the knobs, but I managed to vary within the same intervals as previously and the distortion does not wear off.


(https://i.postimg.cc/2V2RLTKM/20220621-214758.jpg) (https://postimg.cc/2V2RLTKM)
If nothing else then at least a smile somewhere perhaps.

What remains is to wait for July and a tip much awaited from another older thread.
I might be getting some replacement transistors as well, but considering previous attempts I doubt they would make any difference.

frustrating ...

Quote from: puretube on June 21, 2022, 05:25:28 PM
frustrating ...

Thanks, yes quite so. Been  trying to sort it out off and on since February. By no means any record of any sort, but draining none the less

Did you try what I suggested in reply #78 ?

These tests will tell us if some important parts of the circuit are working correctly.

If they do, as i suspect, there would be a good chance that your circuit is ok. Meaning that you are in fact trying to improve the circuit by removing all distorsion (or even just some of it), which seems much more challenging than troubleshooting, all the more so if you aren't an electronic wizard.

Back when I was wondering about some strange connections while my circuit was powered, Chuck D. Bones, a great member of the PedalPCB community, told me that this circuit is supposed to distort the signal, quite easily. He built the same as yours, I am sure he knows what he's talking about.

https://forum.pedalpcb.com/threads/engineers-thumb-compressor-question.12149/

Your circuit doesn't behave exactly like your friend's, or any other similar circuit, because of potentiometers tolerance and values, if I understand correctly.

Nothing obvious can fix this, or Merlin would have already done it. One simple solution would be replacing pots by resistors, as in the 2-knobs version i guess. This way, every settings would (probably) work without distorting.

Mark said something about using LDRs in reply #6, this could be a start, if you want to redesign the circuit entirely, improving the whole thing with clever ideas, which could take years.

Thanks!

Quote
reflow all suspicious pads (and those that look good), hunt for shorts, perform a ritual sacrifice to the diy goddess (while listening to The Bloods),

No, you're right. I still have the ritual sacrifice left. And find out about the Bloods.
I did measure as @duck_arse recommended you. And posted above and my values seemed to check out. Also a full-ish measure of all interesting junctions.

Yes, Chucked helped me a lot on my thread at PedalPCB. Linked at the beginning of this thread. I tried gis suggestions. Then there might have been some slightly more long-shot ones left, but he did not come back with details about those.
I think he breaded in parallel and there is distortion in the more extreme settings for most builders. And as I hope I wrote earlier, this is no issue. But the tyoe of distortion I get at 3&9 (Rat/Thrs) others are not having.
I think me and Wook22 have it, not 100% if you do too, but felt it was less disturbing and opted for a tighter interval setting anyway. But by now, mine is pretty bad in the main part of any useful interval.
I am hoping for sone last ideas in July in another revived thread on my subscription list.
If that does not help I might be willing to "donate it to science"

At the end of this thread is where I am hoping for some more ideas:
https://www.diystompboxes.com/smfforum/index.php?topic=105610.msg951851#msg951851
(https://www.diystompboxes.com/smfforum/index.php?topic=105610.msg951851#msg951851)