SOLVED Can someone please help me troubleshoot a Virgil overdrive?

[aetguitars]

Hi. I built a Virgil Overdrive and everything works except that the gain pot doesn't change anything at all. I tested the pot and it seems to be good.
Can someone help me troubleshoot?
Thanks!

 

[swyse]

Is your issue that its always quite gainy? There isn't a schematic for this project yet, but I believe this may be the minimum gain resistor and its 100k rather than 10k.

 

[aetguitars]

Is your issue that its always quite gainy? There isn't a schematic for this project yet, but I believe this may be the minimum gain resistor and its 100k rather than 10k.

View attachment 50844

Hi @swyse!
No, the issue is actually the opposite... no gain at all.
I checked the resistor you point out against @MichaelW here and it has the same value.

 

[swyse]

It's always hard to tell in pictures especially on these blue resistors, but I thought his had a red band and yours had an orange one, either way if theres no gain then that's not your problem. I'd check for continuity across these spots, I'm not 100% sure if the traces are right as I'm not sure how much the store picture reflects the actual traces, the 220n one would be tricky and have to pull the board so I'd do that last.

 

[aetguitars]

It's always hard to tell in pictures especially on these blue resistors, but I thought his had a red band and yours had an orange one, either way if theres no gain then that's not your problem. I'd check for continuity across these spots, I'm not 100% sure if the traces are right as I'm not sure how much the store picture reflects the actual traces, the 220n one would be tricky and have to pull the board so I'd do that last. View attachment 50845

Yeah, I have continuity on all those spots.

 

[aetguitars]

Found the problem! Bad op amp.
Replaced both with a 4558. There shouldn’t be any noticeable difference vs 4580, right?

 

[aetguitars]

Thank you @swyse for your kind support!

 

[swyse]

Glad you got it sorted! I wouldn't expect there to be an audible difference between a 4558 and 4580 in this circuit.

 

[GizzWizzKing]

Odd that this was the exact same issue Michael had in his build. Good to keep in mind.

 

[Bricksnbeatles]

It’s a known issue, with unknown reasoning. Mine is also two 4558s. By all logic a 4580 should work fine, but Michael, myself, and a few other have run into this issue, and it sounds great as is, so I haven’t given it much more thought

 

[BenB]

I have had the same issue. I tried two different PCBs and neither worked with 4580s. But, once I read your post and swapped out for 4558s I have an amazing pedal! Thanks for posting!

 

[jcpst]

Glad I found this. 4580s from mouser, gain pot did nothing. Swapped for 4558s, now I’m good to go.

 

[Matthewdunne]

Wow! This opamp issue is very strange, I had the same issue- gain pot did nothing. Pulled chips out and place them back in and it worked. I did a second Virgil and it took a couple pulls to get working.