Bass Overthruster problem (solved)

[John Kallas]

just finished mounting it in an enclosure with a relayed true bypass. the strange thing is, on some extreme settings it’s still pulsing in & out (and that’s with a 10K for R6!) but i’m done with it. I’m going to chalk it up to being a somewhat poor design (no offense!) but i do really like some of the sounds that I’m getting out of it,so I’m leaving it like it is.

pics of the build below:

[Barry]

No offense taken, John. I’m glad you’ve found some sounds you like and that you’ve got it working well enough for your purposes. I wasn’t able to reproduce the signal-cutting issue on my own build with either an Allan Woody Epiphone (passive) or Ibanez (active), so without being able to isolate where it’s occurring in yours, I don’t want to speculate about the cause. Thanks for documenting what you found and for giving the project a try.

[John Kallas]

just for the heck of it, i just tried replacing the TL072 with an OPA2134 and it’s no longer cutting in and out on any setting (YAY!). and that’s with an 8K2 resistor for R6, so I’m much happier with it now.

i also have a Powerstage pcb which is nearly the identical circuit so i think i’ll use an OPA2134 in it too.

 

[Barry]

Glad to hear it.

I knew something was up because you had me literally beating the shit out of my pedal with both my Allan Woody and Ibanez, and I just could not make it happen no matter what, and I have a ton of dirt.

Hitting the op amp hard is the point of the design to get that filthy drive, but apparently the TL072 has less margin with some basses/pickups than I anticipated.

I am going to make some mild compromises to account for more basses and bass pickups because they are all a little different.

Thanks for hanging in there with it and for helping me figure this out.

[brd]

And the pedal looks awesome too.

[John Kallas]

no problem. i knew it could be solved with a little tweaking.

[John Kallas]

thanks.

[Author]

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