Engineer's Thumb: Is this issue normal?

[matmosphere]

Post some pictures of the board. Front and back. Maybe you missed a cut or put a resistor in incorrectly. I love buildyon vero but it takes more attention to detail. I've messed up plenty with vero and it can be a bitch to figure out.

[jimilee]

Sabrotone layour is verified, there's even the image of a pedal built. I really can't imagine what is the mistake, indeed, I imagine there's no mistake.
Probably I'll try it on breadboard, if I can trust of my breadboard, it's really cheap, I could try to build it again, but with new parts, I guess I can use the LM13700 and the transistor, and the pots. But I am really disconsolate about this effect. And I can't understand how I could get the same issue with the same IC but a different effect.

How experienced are you with stripboard? We all here still make mistakes. Get yourself a magnifier and look at the bottom of the board. The bad solder joints are hard to see.

And, are you saying you built a different effect with same IC and it didn't work either?


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[JackSkellington]

I really can't see where the mistake could be, I'll do the pictures, but I can do it maybe tomorrow.
I built over 27-28 circuits using the stripboard.

I built just one board, and I changed the Tayda's IC because I suspect it was bad. But nothing changes with a new one from Musikding. THe really weird thing is that I got some years ago the same issue with another LM13700 building an DOD FX25 auto wah. It had a loud attack and a loud tail. I dismess it and I used that LM13700 to build a Snow White, it worked, except the decay pot.

[JackSkellington]

Hi!
I built it again, and this time with all the five knobs. Actually, I guees I never told that I my old version include just three knobs: Level, Ratio and Attack. Following the instruction in the comment I used some resistors e some links to set the Threshold and Release control at max. If I set this two pots at max I get the same issue with the old one I built, and of course the problem get worst when the Ratio is higher.
I found that the problem is the Release control. At 1M is very very high, I can't believe that nobody noticed that. The volume after some seconds encrease a lot and the initial attack is very loud, just before the compression effect starts. The thing get better if I keep the Release pot at 50% about.
I'll do some further tests.

What value did you used for the "Release" resistor?

Zombiesonore had understood something, but maybe fater ask me he miss this topic.

Let me know what do you think about this news.

[zombiesonore]

Zombiesonore had understood something, but maybe fater ask me he miss this topic.

No, I've followed the topic but when Jkokura and Midwayfair jumped in, I humbly leaved the topic because they know better! ;-)
So, after all, you seemed to have experienced the same "issue" that I had with my build. I've used a 1M for "release" and it was unusable... I don't remember if I've finally used something around 470k or a jumper...
 

[JackSkellington]

I didn't try it with this last one I built because it's still without footswitch, but the other one had a loud pop when I engaged and disengaged it. I don't have the old one right now and I can't verify, but I guess this issue occurs just when the release encrease the volume, there's almost no pop when the compression was in action. It was enough pick softly the strings, or make some noise with it to decrease the volume. Else youo get a loud attack before to get a normalize volume.

I just hope that with a release of 470k or even a bit lower I don't have any pop noise when I use the footswitch.
I really can't understand how some people can use this pedal with no regret. And I have to say that I like it enough, but this bug was annoying and dangerous.

[JackSkellington]

Update:

This is the original schematic with the indications for the extra knobs:


Im' having a lot of setting problem with this circuit!
Defintely the 1M Release resistor have to be no more than 470k (like an old version of the schematic I seen). But even the Threshold pot have to be set fine.
If I don set well this two pot/resistor I get several issue I got when I built the first time.
The release increase the volume of the soft picking, and the threshold decrease the volume of the hard picking. I can't play reverse!
I really need to find a good balance. 470k the release (between 1 & 2 lugs). And 220k the Threshold (between 1 & 2 lugs).
Early, I found a good set of this two potentiometers and I get more "compression effect" more attack and fast reaction and squishy, that I liked, than the version with fixed resistors. But trying again now I have some distortion (I have no leds). Anyway, with Ratio at max the issue tend to come up again. I would like to set it fine even with extreme settings.

[JackSkellington]

Sorry for the third post, but I'm really disturbed about this circuit!

Looking some version of layout, schematic, document, etc... I found a different suggestion to replace the 1M threshold resistor.
Sometime it is just a variation of that value, so we need the lug 1 and the lug 2 and 3 connected together to change that value. Sometimes, how the Sabrotone layout does, the lug 2 of the pot goes to the positive of U1b, the lug 3 to the 4.5V the lug 1 to the positive of the U1a.

Having the Threshold and the Release pots should give us more setting, but the setting of this two pots are very tricky and get the way to play with this compressore is really dinamycally unnatural. I have to play softly to get loud and I have to play hard to get less volume!

It shouldn't be my mistake, because this is my second Engineer's Thumb and the issue is the same.
I could set the Release with a resistor, and for the Threshold a resistor or a trimpot (flying, probably). It depends from the right wiring of it.

[jkokura]

Not sure if you've posted this already or not, but what PCB layout are you using for this circuit? I only ask, because if you're using something that's unverified, then I'd want to examine the layout to see if there are issues.

Jacob

[JackSkellington]

Hello, I have a problem with the Engineer's Thumb using Sabrotone layout.
https://www.sabrotone.com/?p=2901
All the informations about it, here:
http://www.valvewizard.co.uk/engineersthumb.html

The effect seems work, a sort of, indeed I get the compression, but with some weird issues.
When I don't hit the strings I can hear the hiss and the volume rise up, and when I hit the strings I get a loud attack, then the compression act and I can play normally, though I got another strange thing: depends by the settings, but if I hit the strings harder the compression low the volume more than when I play softly.
I think this depends from the volume that rise up too much, it cause the loud attack and the loud volume when I play softly.
This issue cause a third problem. When I wired it into the box with footswitch and all the rest, this loud attack cause a high pitch snap when I switch off the effect, especially after I waited 6-7 seconds the release time.
[...]

That was my first stripboard, where I followed the instructions on the Sabrotone page to set fixed resistors for Threshold and Release, both at max.
Here's my update image with instructions included:


I included even the two leds (you can see in the original schematic in Valve Wizard page) in my first board. I didn't notice changing, but maybe it was because the Threshold and Release settings.

I can get a better usability, though a have little distortion in the peak in the attack with humbucker, and just at high setting of the Ratio. This time I don't have leds. I hope that will help.

To adjust the setting, after some test, I could set the Release resistor around 330k, but for the Threshold I have to understand the right replacement of that resistor. Just change the value of 1M or get the dual action of a trimpot.

Here's the original schematic, 2016:


Sabrotone version is based in the 2012 schematic version, just some little difference.
- C8: from 100nF to 1uF. Less noise?
- Release resistor was 1M but now not over 470k and not under 100k.
- 33R in line from the 9v (I think to reduce noise).
- 1k resistor (R11) left out and replaced with a jumper between pin 4 of LM137000 adn pin 6 of IC2 TL072 (look Sabrotone Layout). I don't know why.

Edit:
It's been even used some parts of the LM137000 early not used.
And I just noticed that there's a newer version of the schematic, with some adding and modified parts.
I just would that my version work fine and not so weird.