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Projects => General Questions => Topic started by: JackSkellington on November 05, 2018, 11:27:11 AM

Title: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 05, 2018, 11:27:11 AM
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.
This snap is barely audible when I engage the Vemuram Jan Ray (in the same box).
I tried anyway to use a pulldown resistor input or output, but the problem is in that big boost of the compressor.

I really need help, the pedal is for a friend.

Thanks!
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: zombiesonore on November 05, 2018, 11:42:12 AM
Hi.
I've build one this summer, maybe I'll be able to give you some help.
Do you have build the full 5 pots version?
I remember, when using this version, that a good clean compression could be hard to get. The pots interacts at lot.
Please let me know how you sets each pots.
 
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 05, 2018, 11:52:41 AM
I'm using just three pots. Ratio and Volume and Attack. I followed the instruction to exclude, or better to keep the fix value for the other pots.

The compression sounds clean and nice (not distorted), but I get this thing really strange to me, that make this compressor a bit hard to play without the right touch. And I get this loud volume after the release time. This cause the loud attack of the first hit, and probably the loud snap when I switch off.
I guess that the overdrive effect after the Engineer's Thumb attenuates the snap becuase it attenuates even the compression.

Edit: The LM13700 come from Tayda. Some bad experience with this chip from Tayda?
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: zombiesonore on November 05, 2018, 01:14:46 PM
What value did you used for the "Release" resistor?
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 05, 2018, 03:38:27 PM
You can find the instructions to exclude the Release, Threshold and Attack pot on the Sabrotone page.
Anyway, I used 1M resistors for Threshold and Release, I guess it should be like if both was at max.

By the way, this kind of reaction I found it some years ago when I tried to build an auto wah DOD FX25, using an LM13700. Even this effect was sensitive to the picking (like the compressor). When I let it for a few seconds and then I hit the strings I got a quick loud bump of low frequency before the normal volume wah sound of the effect. The same things when I let the strings release by their self, the same loud bump of low frequency in the tail of the decay of the wah. Unusable, so I rejected.

Thinking this now I get the exact thing, though with a different effect: in this case I have a bump of volume.

Unfortunately, I have just another LM13700, even this bought from Tayda, it is right that LM13700 coming from the dismissed DOD FX255, now used for a Snow White Auto Wah, without this bad issue but with an unexplained not working Decay pot that I left anyway.

Or both this LM13700s bought with at least three years of distance are defeated, or all the LM13700s coming from Tayda are defeated. Or all this behaviour is normal and I don't know what mess I did.
Anyway, my Engineer's Thumb sounds too weird to be normal and usable with no worries.

This building is enough urgent. :-[ :-[
Thanks for the help.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: jkokura on November 05, 2018, 08:25:38 PM
My first thought was either your chip is bad or you've got parts in the wrong places. Perhaps you've got the wrong value in one of the key places?

Perhaps walking through the debugging steps and ensuring the parts values and orientations, swapping out the chip, taking some measurements might help.

Jacob
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: midwayfair on November 05, 2018, 10:28:05 PM
The thumb clamps down pretty hard after the initial attack. I'm not sure if that's what you're talking about.

There's absolutely a compression artifact where the first note's attack is significantly louder than the rest of the compression. I didn't notice it as much with my guitars but with higher output pickups I can't unhear it.

I stopped building these because I wasn't able to satisfactorily deal with it without using the input LEDs, which will add distortion with high-output pickups.

If you didn't use the input LEDs, add those first and see if they help.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 06, 2018, 02:09:27 AM
I prefer the chip is bad, because I didn't see anything wrong. But I'll check again.
I'll take out the chip for the measurement, too.

What I get is right a loud initial attack. When I play harder I get less volume than when I play softly, but this maybe depend from the settings, and this could be almost handle. But the loud attack is a bigger problem, especially when cause the loud snap when I turn off the effect. It's not the usually pop, but an high pitch click.

Later, I included even the two LEDs, but the problem was the same. Initially I didn't think this issue was a thing so bad. But now with the footswitch... I can't give this pedal to my friend.
He should engage the overdrive before to turn off the compressor. Not so cool.

Edit: I bought these two LM13700 from tayda, when the cost was 1,50 $. Now it's 2,02 $. Musikding has it at 1,75 Ä.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 06, 2018, 04:05:09 AM
Voltage LM13700:
1 - 2.24v
2 - 0v
3 - 4.50v
4 - 4.49v
5 - 4.49v
6 - 0v
7 - 0v
8 - 0v
9 - 0v
10 - 0v
11 - 0v
12 - 0v
13 - 0v
14 - 8.99v
15 - 0v
16 - 0v

I measured it without the LM13700 and without cables.

Resistors value are correct, as well the orientation of the BC327 and the diodes. Caps orientation and value correct. Position of the components is right.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: midwayfair on November 06, 2018, 07:52:50 PM
I prefer the chip is bad, because I didn't see anything wrong. But I'll check again.
I'll take out the chip for the measurement, too.

What I get is right a loud initial attack. When I play harder I get less volume than when I play softly, but this maybe depend from the settings, and this could be almost handle. But the loud attack is a bigger problem, especially when cause the loud snap when I turn off the effect. It's not the usually pop, but an high pitch click.

Later, I included even the two LEDs, but the problem was the same. Initially I didn't think this issue was a thing so bad. But now with the footswitch... I can't give this pedal to my friend.
He should engage the overdrive before to turn off the compressor. Not so cool.

Edit: I bought these two LM13700 from tayda, when the cost was 1,50 $. Now it's 2,02 $. Musikding has it at 1,75 Ä.

It actually sounds like you might be talking about something different from what I was, then. The click I was talking about was fairly subtle and the LEDs clip the initial signal a bit to prevent it, so if it's really that noticeable you might have something else going on.

I've definitely had bad 13700s from Tayda. To the point where I wasn't sure they really were what they said on the package.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 07, 2018, 02:25:27 AM
I really would like to solve changing the LM13700. That will be so easy!
By the way, I tried, just to be sure, the other LM13700 (Tayda) from the Snow White (without this issue, but with a not working Decay pot, as I said. Maybe there's a link?) and the result is the same.

To tell this issue with few words the effect (the LM13700?) work, but bad. Because I guess it boosts too much, so I got this very loud initial attack (at least three time the normal volume), and, I'm trying to guess, for the same reason I heard this high pitch click when I switch off the effect after the release time, and a bit when I turn on, It's not the usually bump when we got without the pulldown resistor. And I got a bit too much volume jump: louder when I play softly (because the too much boost) and less loud when I play harder (because the compression, perhaps the good working part).

This issue is absurd, the Engineer's Thumb has pro and cons, but I get an effect unusable, I don't think that nobody notice this, except me. :o

The funny thing is that the same loud initial attack I got in the Auto Wah DOD FX25 I dismessed, it was loud even in the decay, just with a bunch of low frequency, but that was the wah effect like in the heel position.

Midwayfair, how did you realize that Tayda had bad LM13700 chip? It doesn't work at all or you got a sort of issue like me?

By the way, I even more sure I'll never buy transistors or ICs from Tayda.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 09, 2018, 03:33:24 AM
I ordered a new LM13700 from Musikding. Waiting to test it. ::)

I also ordered some stuff I usually order from Tayda.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 16, 2018, 09:04:04 AM
Hello guys, I'm really disappointed, mad and desperate with this effect. I replaced the Tayda's LM13700 with a Musikding's LM13700 (it looks printed finer), but the problem persists.
It's like a big boost that causes a really too loud initial attack and the snap when I disengage the effect.
I tried even to replace the BC327 with another one bought from Musikding. But nothing.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: jkokura on November 18, 2018, 07:09:03 AM
I wish I could offer more for you than to keep working the debugging steps, or try again. I don't know if the Sabrotone layout is verified or not, I suspect it is, but you can never rule out our own mistakes. I'd try it again at the stage you're at now, although I'd reuse whichever parts you can from the first try.

Jacob
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 18, 2018, 12:58:12 PM
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. ???
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: Matmosphere on November 18, 2018, 01:19:49 PM
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. Iíve messed up plenty with vero and it can be a bitch to figure out.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: jimilee on November 18, 2018, 03:33:48 PM
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 didnít work either?


Sent from my iPhone using Tapatalk
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on November 19, 2018, 02:33:16 AM
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.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on March 03, 2019, 03:07:09 AM
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.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: zombiesonore on March 03, 2019, 07:21:32 AM
Quote
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...
 

Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on March 04, 2019, 02:10:49 AM
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.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on March 04, 2019, 11:13:33 AM
Update:

This is the original schematic with the indications for the extra knobs:
(http://www.valvewizard.co.uk/engineersthumbschem.jpg)

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.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on March 06, 2019, 03:19:16 AM
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.
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: jkokura on March 06, 2019, 10:34:28 AM
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
Title: Re: Engineer's Thumb: Is this issue normal?
Post by: JackSkellington on March 07, 2019, 02:17:18 AM
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:
(https://i.imgur.com/vNd6NlR.gif)

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:
(https://i.imgur.com/WyMO7hT.jpg)

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.