thanks, definitely food for thought in the tone i seek. ok, it looks like i was half in the right ballpark. i thought it would be C7 and C9 because those are the two you replace with a single 220nf to do the tone bypass mod. if it’s not too much to ask could someone figure out which C and R numbers in the opamp schematic correspond to which C and R’s in the duncan tone stack calculator? i just can’t figure it out completely. maybe then i could experiment there a bit with some values before doing it in the pedal.