SOLVED Gain Pot (Knob) Does Nothing

M

Mr. Strypes

Member
I decided to build the Virgil today. (Bad monkey! Bad!) Everything works fine other than the gain knob, which does nothing. What I have currently is a limited EQ pedal. Level, low, and high pots all work, but the gain does nothing. The sound is clear and clean.
I resoldered that section of the board to make sure there was good connection. The gain section still does nothing.
I also replaced IC2 with a new JRC4580. Same issue.
(I get the same results inside and outside the enclosure.)

Using a DMM, I checked the gain section of IC-2 (pins 1 and 2).

The resistance (unpowered) between pins 1 and 2 is 9k94

The voltage reading (powered) for:
Pin 1: 5.37 v
Pin 2: 5.32 v

I have no idea if those numbers are correct.

Side note: I noticed that the unit's power draw is 33 mA, which seems to be high.
 

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swap the 4580 for something else like a 4558 and see what happens.

almost everyone that has built one of these with 4580 has had issues.
F

DEMO Post in thread 'Virgil Overdrive (Digitech Bad Monkey)'

Adding another report that 4580 led to zero change with the gain pot. Changing out to 4558 allowed the gain pot to do it's job. I tried with NE5532 which responded the same as 4580 - any changes in the gain knob were imperceptible. I just swapped everything over to 4558s, same as every other pedal. Tossed all the 4580s despite having a wide variety of lot codes, didn't work in virgil or pathos.

MichaelW

DEMO Thread 'Virgil Overdrive (Digitech Bad Monkey)'

So I guess I missed all the controversy as of late for this pedal involving JHS. I'm not exactly sure what the controversy was and too lazy to look into it too much (and really don't care.... :ROFLMAO: )

But out of curiosity I built the pedal and tbh I think it sounds great!

You could say it's a YATS with a Bandaxall tone stack and wouldn't be too far off but the eq is pretty powerful and can pull some of the mids out.
It reminds me a bit of the Boss OD-1 (Oddity) but with more eq control and more bass. It can be pretty "big" sounding.

But I found that my favorite sound was with the...
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owlexifry said:
swap the 4580 for something else like a 4558 and see what happens.

almost everyone that has built one of these with 4580 has had issues.
F

DEMO Post in thread 'Virgil Overdrive (Digitech Bad Monkey)'

Adding another report that 4580 led to zero change with the gain pot. Changing out to 4558 allowed the gain pot to do it's job. I tried with NE5532 which responded the same as 4580 - any changes in the gain knob were imperceptible. I just swapped everything over to 4558s, same as every other pedal. Tossed all the 4580s despite having a wide variety of lot codes, didn't work in virgil or pathos.

MichaelW

DEMO Thread 'Virgil Overdrive (Digitech Bad Monkey)'

So I guess I missed all the controversy as of late for this pedal involving JHS. I'm not exactly sure what the controversy was and too lazy to look into it too much (and really don't care.... :ROFLMAO: )

But out of curiosity I built the pedal and tbh I think it sounds great!

You could say it's a YATS with a Bandaxall tone stack and wouldn't be too far off but the eq is pretty powerful and can pull some of the mids out.
It reminds me a bit of the Boss OD-1 (Oddity) but with more eq control and more bass. It can be pretty "big" sounding.

But I found that my favorite sound was with the...
  • Like
  • Love
Click to expand...
Holy moly, it worked! Thanks, bro! I was wracking my brain trying to figure out what I'd missed.
 
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Nostradoomus said:
ballsy move writing digitech right on it
Click to expand...
Yeah, I know. I don't plan on selling it or anything. After a couple hundred builds, I became concerned that I'd eventually start forgetting what some of the pedals were based on. You've been at this longer than me, though. Is that something I could get prosecuted for, Nostradoomus?
 
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owlexifry said:
damn that's a cool print.

wish i had a clue about that stuff 😓
Click to expand...
It took a lot of practice. I use a Word doc. I insert a picture of the drill template from the build guide, then put a rectangle with rounded corners over it. The rectangle's dimensions are 2.44" (W) x 4.64" (H). Then I insert text boxes for each of the knob labels. Next, I insert an image (sometimes drawn, sometimes downloaded, sometimes AI generated). I right-click and send the picture to the back, then right-click and bring it forward so it's in front of the drill template. From there, it's just adjusting the position of the picture and changing fonts. Finally, I print it on glossy photo paper. I use an inkjet printer, and it seems to work fine (versus an inkjet). Oh! I lightly spray the print with my wife's hairspray. LOL! Hairspray acts as the perfect protective lacquer. I let it sit for 24 hours so it dries thoroughly.
 
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Mr. Strypes said:
Yeah, I know. I don't plan on selling it or anything. After a couple hundred builds, I became concerned that I'd eventually start forgetting what some of the pedals were based on. ...
Click to expand...


That's why some people use something similar, like if the pedal is called "2000lb Bee", they'll call their pedal the "Heavy Wasp" — all the DIY PCB suppliers are already doing it, for the most part*. Everybody has a clone of the TS-808, for example, commercial pedals and DIY suppliers alike, so the good names get used up pretty fast...

Of course, I'm not telling you anything you didn't already know.


Here's the reason behind my post, a suggestion:
Name your builds whatever you want, can be completely unrelated to the original pedal it's based on — then with a permanent-ink pen/marker or a paint-pen, jot down the original name on the front vertical face, the back (partially hidden under the top-jacks), inside on the lid — whatever/wherever your preference.

Again, I offer nothing new, just a reminder of what could be done.


ASIDE: What is with this circuit? Robert is a stickler for PPCB's accurate reproduction of a circuit, so the original BMs must've had the 4580 — so why does the commercial version work with the 4580, but not the Virgil? I don't recall there being a successful 4580-Virgil yet.
🤷‍♂️
👖


Your pedal...
Great graphic, very-good-looking pedal.
Thanks, too, for sharing your graphics method. My builds need graphics, so I'll give your method a crack.









*Only just now, did I look up "Virgil the monkey" — I didn't even know there was a show called Muppets Tonight ! If that's even what the obscure Virgil reference is making the connection to the Bad Monkey...
Hmm maybe I'll name my build "The DODgee Monkeh!" GRAPHIC: Ed Roth style...Have a Green Monkey in a monk's robe (instead of Ratfink) driving a classic Dodge convertible, something like this:

2c8b50920f3a5d2925e41209d4854233.jpg
 
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Feral Feline said:
If that's even what the obscure Virgil reference is making the connection to the Bad Monkey...
Click to expand...

www.imdb.com

Project X (1987) ⭐ 6.2 | Comedy, Drama, Sci-Fi

1h 48m | PG
www.imdb.com www.imdb.com

Feral Feline said:
ASIDE: What is with this circuit? Robert is a stickler for PPCB's accurate reproduction of a circuit, so the original BMs must've had the 4580 — so why does the commercial version work with the 4580, but not the Virgil? I don't recall there being a successful 4580-Virgil yet.
Click to expand...

Your guess is as good as mine... I need to build another one so I can play around with it a bit more.

The only thing I can think of is some sort of parasitic oscillation that the 4580 doesn't like. It's not a particularly high gain circuit nor is the layout overly crowded, so it's puzzling for sure.
 
Last edited:
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Oh right. I DO remember the Project X reference now, mentioned elsewhere on the forum. Never saw the movie, though, so I guess that's why I forgot the reference.

Maybe the BM you got to trace was an aberration ... nope — all gutshots on the web I can find clear enough to show the chip show 4580.
Maybe Digitech craftily relabelled all their 4558s going into their BMs, to thwart the cloners... It's a con's piracy Italia.




Aside from that: Why does searching "Virgil the Monkey" link to Muppets Tonight host "Clifford"?
Still... doesn't "Virgil" nee "Clifford" remind you a bit of Tim Minchin❓

Clifford muppet.webp
9da83fb9d400b242d26e05dc24f757ca.jpg


Coincidence⁉️ I THINK NOT‼️
 
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