Dual boost strange behavior

[rankot]

Just finished dual boost pedal - one half is Zazen Boost by Andy, another half is old-fashioned JFET boost. I put a switch, so I can pick which one is making output, and they both share the same input circuitry. dDRIVE pot affects only JFET boost, but when I switch to that one, rotating zGAIN pot also affects tone slightly, although output of Zazen Boost is disconnected (see schematic). I can't figure out why does this happen???

[iainpunk]

it might be wise to also disable any interaction going in to the inactive circuit with a DPDT selector switch, instead of SPDT.

cheers

[rankot]

You are right, I'll try that, too.