bluesbreaker with drivemaster eq

[fixxe]

Alright, I finally got around to build this. I marked the cutting point for both circuits at the 1k resistor, taking the BBs overdrive and the Drivemasters tonestack.
Problem now is, that the engaged pedal is very quiet and I don't get any distortion. Could it maybe be, that the tonestack now needs VRef instead of going to ground? Or what could be the problem?

[RobA]

I think you'll need the output cap from the gain stages before the Marshall tone stack (C12 on the schematic, the 220nF).

I'd start there, but I'm not sure that's going to fix everything. The volume losses in the two output sections could be very different and that might be made up by the different input levels into them. It could be that you need a simple gain stage after the tone stack to make up some of the lost volume.

Which parts did you include in the initial gain stage? If you were to use the parts listed as alternates on the schematic, it seems to me that you wouldn't have much gain going into the second stage.  It didn't list it, but is the "Gain" pot supposed to change too if you change the two resistors?

[fixxe]

Thanks for the detailed reply. I used the normal values for the bb. I'll try the 220n cap. If that doesn't work, do you have the schematic of a good gain stage?

[RobA]

Thanks for the detailed reply. I used the normal values for the bb. I'll try the 220n cap. If that doesn't work, do you have the schematic of a good gain stage?

It depends a bit on what you want to do, op-amp versus transistor, etc. but the output transistor stage from the Big Muff would work. You'd need to adjust the resistors to get the right amount of gain and fix the bias point for that, but it'd be pretty easy to do.

If the circuit doesn't work right after you add the 220nF cap, then I'd audio probe the circuit at that point to see if you are getting enough volume before it hits the tone circuit. It could be that there is something happening before that point.

Edited: I don't know if you can do this at the point you're at in this build, but if I were doing this from scratch, I'd add in an op-amp based output boost and then use the second op-amp from the pair as a buffer for the bias voltage. Not that this is really needed in the circuit, but it'd be pretty much the easiest thing to do and it would help a bit.