Thumb Sucker Compressor "scrapy" sound

Matopotato

Matopotato

Active member
Hi,
I just "finished" building a Thumb Sucker Compressor. Sounds very cool, more impressed than I had expected.
But..
1. There is an element of distorted scratchy sound. More with humbuckers than single coils. It is not distortion as you would like from a distortion pedal. More scratchy. It is all in the box so I doubt there is some loose cable or joint (famous last...). I am not very used to the controls yet, but it seems to vary with very low setting on release but maybe not. More so with (higher) ratio above 12 and (lower) threshold below 10-12...
(2. The attack and release knobs. Checked connection and that seems to be all good at least in that vicinity of the board. But they do not change things much. Is it because they are that subtle? Or do they only come in play with other settings? (CORRECTION: Asked this here as well: https://forum.pedalpcb.com/threads/thumb-sucker.6769/ post #6 I think. sorry for double posting))
 
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Settings I moved around a bit with, but about:
RATIO 1:30
THRESHOLD 2:00
ATTACK 10:00
RELEASE 2:30
VOLUME 2:00
Bright: On

As I let a chord ring out, it is clearly suppressed at the beginning, but it gets more and more "released and increased".
There is an oscillation in there and at the end distortion. I would guess this distortion is the same nature as discussed above and as you showed @Chuck D. Bones in your graph due to the compressor pushing harder with the diminishing signal, so my settings are probably not optimal for keeping things clean.
Still curious if this is much less or much more the case with ThumbSucker.

Can Irun it at 12 or 18 volts to increase the headroom? Or is that not going to help out with my issue...

Some sound samples. I felt SC were more prone to the distortion and less reduced when dialing down guitar volume (not really in the clip) than the Humbucker.

Single Coil into Marshall DSL (You hear the slight oscillation, and at 0:10 the scraping)
EDIT: Better sample
https://soundcloud.com/user-558594533%2Fthumbsucker-sc-2


Humbuckers
https://soundcloud.com/user-558594533%2Fthumbsucker-hum
 
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It seems the electrolyte caps are 25V or more, The LM13700 can take 36V and the TL072 more. The film caps take 100. The diodes and 3mm LEDs and a 100pF ceramic I don’t know...
Will await confirmation or educated guesses before trying to fry anything
EDIT: And 2N3906 should manage 60V it seems, ar least 18V
 
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Many thanks. Yes, I saw that page.
Couldn't figure out what the 3mm LEDs can take, but they seem to be where I am wild guessing, 18V wouldn't hit them too hard?
Would you think engineer's thumb is a less distortion prone build? IMHO, they seem to be very similar in schematics though...

Would the RELEASE below noon reduce the slightly wobbly oscillation aspect?
 
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18V power won't stress the LEDs. You might want to increase R100 so that the ON/OFF LED isn't blinding. I recommend increasing R10 to 1.8K-2.2K for 18V operation.

Try the lower RELEASE setting. I think the wobbly decay you're hearing may be caused in part by feedback from speakers to strings. Try headphones with the speakers off and see if the wobble is still there.
 
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What would be the negative impact of having R10 on 1k while trying 18V?
And would say 2k cause provlems for 9V?
Thinking of having some switch or similar or just setting it to either fixed value
 
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R10 and Vref determine the max current thru Q1 and into the control pin on IC3. We know the existing combination works with 9V power. If we increase the voltage, Vref goes up too because Vref = 1/2 Vcc. When Vref goes up, the max control current goes up. At that point, we're sailing off the edge of the map and we don't know if the result will be good or bad. I'm not convinced that raising the power supply voltage is necessary, so I don't plan on testing or analyzing the high voltage case. After I spend some time with my breadboard, I might change my mind. My working assumption is that Valve Wizard knows what he's doing and the design is sound.

If you want to run it on 12V or 18V, feel free, you're not going to break anything. Leave R10 alone for the time being.
 
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Great, thanks. I got the idea from Jacob at Origin Effects where he mentioned that more headroom could alleviate one of the two main distortions:
"Either you run out of headroom and you're causing a clipping style distortion, or you have really aggressive compression settings and the compressor starts to fight itself."
My case might be woth the latter, but you graph got me thinking of clipping.
So I am willing to try. And will share any findings.
 
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it is also possible that you have different kind of compressor in your mind. Something that squeezes the signal more to give a lot of sustain without necessarily killing the dynamic range of the incoming signal. Some compressors let you blend in a clean channel with the compressed sound to give you the benefit of the dynamic range plus sustain.
 
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zgrav said:
it is also possible that you have different kind of compressor in your mind. Something that squeezes the signal more to give a lot of sustain without necessarily killing the dynamic range of the incoming signal. Some compressors let you blend in a clean channel with the compressed sound to give you the benefit of the dynamic range plus sustain.
Click to expand...
Yes, the talk with Origin was around their Cali76 CD vs Stacked, and if distortion is inherit in compression when you dial in extremes (IMHO, it is)
 
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Findings:
I put on headphones, and turned off the speaker. There is still that sort of oscillation. Like a tremolo on low depth and mid to slow rate. I flipped the speaker on and off but it had no impact as far as I can tell. I am quite untrained in compression though (still can't hear ATTACK knob effect, but I am getting there...)

9V I have already written about the noise issue. 18V and it was gone. Like really gone. I had RATIO maxed and THRESHOLD "minned". Then I discovered I had left some reverb on. Turned that off and, yes there is still some distortion on 18V, but when going back to say RATIO 03:00 and up with THRESHOLD to 09:00 it was very hard to hear, if any.
Flipping between 9 and 18V was very telling.
Only downside with 18V is that the volume dropped quite a bit, so I had to compensate more with LEVEL, which just adds a touch of distortion but not nearly as much as with same "output level feeling of sound" as with 9V.
The 3mm LEDs inside didn't react. And the 5mm on/off led is the same brightness regardless of DC input voltage.

So I have learned I have to get to know compression more and then use it wisely. It is not like any other kind of pedal where the extremes and all combos "work", but more delicate and interaction and dependencies has a bigger role.
And 18V will probably be what I use until I understand the nuances better.

Plans:
I like to tweak. Even my first kit build I could not help changing it. The big upside with DIY is price of course, but in my case maybe even more the control of adding stuff I would like.
(I made my own distortion based on a Brian Wampler video on how to build your own distortion. I ended up putting 17 diodes for clipping in different constellations, using two rotary switches that eventually got so "thick" with all cables and soldering that I could not close the lid without quite a bit of force. But I got what I wanted...)
So all that said, I will most likely go ahead and add some R10 option even if @Chuck D. Bones advised me to leave it alone. I am thinking a socket and then I can swap in and out 1k or ~2k if I flip between 9 and 18V in a sort of semi-flexible way...

Is there something else I ought to change if running on 18V, especially to bring up some more volume? Or better to just turn LEVEL knob as needed?
 
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zgrav said:
Biggest surprise for me is seeing that Jack Orman is still putting up new articles on his site. Very good to know. Thanks.
Click to expand...
Made me happy 😀
Planning on doing his take on mxr dist + with all the variants on clipping, and if ok, take the ones I like into another crazy build

EDIT: He posted on DIYstompboxes.com under Pictures where he linked it.
 
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So with THRESHOLD on minimum setting, there is not a whole big difference between 9 and 18V. At noon, there is nothing to think about, 18V drops in volume in comparison. I A/B with same settings and on/off.
Strat
Bright on
ATTACK min
RELEASE 10:00
LEVEL 01:30
RATIO 12:00

I am also surprised, I thought 18V meant "more"... I run OCD and MXR Clean Boost on 18V and they are "more loud"
 
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Chuck D. Bones said:
R10 and Vref determine the max current thru Q1 and into the control pin on IC3. We know the existing combination works with 9V power. If we increase the voltage, Vref goes up too because Vref = 1/2 Vcc. When Vref goes up, the max control current goes up. At that point, we're sailing off the edge of the map and we don't know if the result will be good or bad. I'm not convinced that raising the power supply voltage is necessary, so I don't plan on testing or analyzing the high voltage case. After I spend some time with my breadboard, I might change my mind. My working assumption is that Valve Wizard knows what he's doing and the design is sound.

If you want to run it on 12V or 18V, feel free, you're not going to break anything. Leave R10 alone for the time being.
Click to expand...
I heard the sound clip and there was similar oscillation at the end. So nothing wrong with my build, it is part of the deal.
 
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Matopotato said:
Findings:
I put on headphones, and turned off the speaker. There is still that sort of oscillation. Like a tremolo on low depth and mid to slow rate. I flipped the speaker on and off but it had no impact as far as I can tell. I am quite untrained in compression though (still can't hear ATTACK knob effect, but I am getting there...)

9V I have already written about the noise issue. 18V and it was gone. Like really gone. I had RATIO maxed and THRESHOLD "minned". Then I discovered I had left some reverb on. Turned that off and, yes there is still some distortion on 18V, but when going back to say RATIO 03:00 and up with THRESHOLD to 09:00 it was very hard to hear, if any.
Flipping between 9 and 18V was very telling.
Only downside with 18V is that the volume dropped quite a bit, so I had to compensate more with LEVEL, which just adds a touch of distortion but not nearly as much as with same "output level feeling of sound" as with 9V.
The 3mm LEDs inside didn't react. And the 5mm on/off led is the same brightness regardless of DC input voltage.

So I have learned I have to get to know compression more and then use it wisely. It is not like any other kind of pedal where the extremes and all combos "work", but more delicate and interaction and dependencies has a bigger role.
And 18V will probably be what I use until I understand the nuances better.

Plans:
I like to tweak. Even my first kit build I could not help changing it. The big upside with DIY is price of course, but in my case maybe even more the control of adding stuff I would like.
(I made my own distortion based on a Brian Wampler video on how to build your own distortion. I ended up putting 17 diodes for clipping in different constellations, using two rotary switches that eventually got so "thick" with all cables and soldering that I could not close the lid without quite a bit of force. But I got what I wanted...)
So all that said, I will most likely go ahead and add some R10 option even if @Chuck D. Bones advised me to leave it alone. I am thinking a socket and then I can swap in and out 1k or ~2k if I flip between 9 and 18V in a sort of semi-flexible way...

Is there something else I ought to change if running on 18V, especially to bring up some more volume? Or better to just turn LEVEL knob as needed?
Click to expand...
Did you run it at 12V? Just wondering if that makes any difference with respect to the Threshold?

Just wondering if the extra power affects that.
 
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