For the Phase Inverter Master Volume in this circuit - is there any reason to use a push/pull POT to completely remove it from the circuit when not in use, or is a standard 1M Audio pot a good choice here. It's pretty much the easiest thing to swap out. I have mine mounted on the rear of the chassis so i just need to fly a couple of wires over the circuit board. I tested it out with some alligator clips a few days and and it seems to work fine. I'm thinking - and i don't know why i didn't do this out of the gate - of adding an impedance selector switch to the rear here. Anyone have any advice on where i should: add a selector switch (which means drilling another hole) reclaim the line-out jack and wire it as a second impedance speaker output I'm leaning this way as i hate drilling a hole in completed amps if i can avoid it and i don't think i'll use the line out.