DEMO Virgil Overdrive (Digitech Bad Monkey)

[MichaelW]

So someone smarter than me would have known this without even trying it, but flipping Q2 around makes it act like it’s not even there. I ended up putting Q2 back in…decided it does actually help control the bass in a usable way.

So you flipped backwards from the board silkscreen?

 

[Gsatterw]

So you flipped backwards from the board silkscreen?

Yes. It makes it like it wasn’t even installed.

 

[maertz13]

can anyone with a fully functioning BM measure and post what the bias on Q1 is? and if mine is low, can i adjust R4 to compensate? the J201's i source tend to be a little inconsistent

 

[falkry05]

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.

 

[southpaw-dd]

Glad I found this thread! I'm having the same issue with the gain knob not changing the signal (looks like unity gain through the op-amp on o-scope). Changing to 4558 did not help my situation - both sets of op-amps purchased through Mouser. Any other ideas?

 

[MichaelW]

Glad I found this thread! I'm having the same issue with the gain knob not changing the signal (looks like unity gain through the op-amp on o-scope). Changing to 4558 did not help my situation - both sets of op-amps purchased through Mouser. Any other ideas?

Did you try the 4558 on both IC positions?

 

[southpaw-dd]

Did you try the 4558 on both IC positions?

Hey @MichaelW - yes, tried that and didn't have any luck. I may have a different issue because I found a bad WIMA film 220n cap in that part of the circuit and replaced it, then the signal looked much better, but resulted with the 'unity gain' issue using both 4580s and 4558s (in both IC spots). I'm wondering if the 220p op-amp cap needs to be replaced, too. All of the resistors were checked and they are good.

 

[MichaelW]

You might want to start a thread in the troubleshooting section and get some help.

 

[fuzztone]

Thank you forum people for your valuable insights. I just did the swap to 4558s from 4580s on my Virgil, and my gain pot now responds as it should. My 4580s have code C135A. Again, thanks for saving my project.