For anyone else who has built this, do you get popping when you switch channels? Bypass is totally quiet, btw. Tried both wiring versions, same result. I never noticed at low volume, but now gigging with it...
I'd try two things... First, drop RPD down to 1M or so (it's specified as 2.2M). Second, add a 100k output pulldown resistor at the junction of R89, D1 and D2. This may help to bleed off DC that leaked through the C38, the output capacitor. I don't think this will have any impact on the tone but it will affect the output impedance slightly. (putting it more in line with what you'd see on a pedal) You'll have to just wire it to the nearest ground pad.
I haven't tried either of these, but comparing it with standard circuit that doesn't pop, these seem to be moves in the right direction.
Thanks for the suggestions. I used a 1M for RPD originally, and tried the 100k to ground, but no change. I'm considering a workaround involving a momentary switch to ground the output while changing channels. Unless there are other possibilities that might solve for this. It's too great to not have it on my gigging board!