Thanks all. I did indeed try moving wires around with a non conductive stick to no avail. My heater circuit at this point seems as tightly wound and away from signal wires as any other example i’ve seen.
I’m no expert but it would seem to be a grounding or pot thing, right? Why would the hum go away at 12? If it were heater circuit, wouldnt the humming either be there or be worse at 12?
Any reason not to star ground everything? It would not be difficult to add 4 wires to individually ground each pot, the input jack, and the filter caps/220kohm-500ohm resistor junction.
Any reason to suspect the pots? I bought both regular 1M pots and these expensive plastic element ones. I could try the regular ones for kicks.
Also, I’ll switch over to the 125V power tap and see if that lowers my voltages any, and double check the heater circuit voltage before/after.
Thanks again for all your help – seeing the hum almost disappear at full volume makes me think i should be able to get it there at all volume levels, and then this would be one hell of an amp.