do you agree that according to the layout drawing in post #5, the only path back to the HT CT from V1 (as well as V2) is via the input jacks and chassis?
yes. There are other paths to the chassis as well, like thru the volume pot, but what you suggest is the only direct path with very little resistance.
You did say, "I don’t think it will happen the way that your wiring diagram is wired,"
I meant that I did not see how AC ripple in the DC operating current is going to affect the signal at the input Jack.
I was agreeing with your assessment of the current flow. I just then understood the current path through the black wire at the U turn.but then in a later post you said, "that is the way I see it too,"
Fwiw, by "input jacks," I mean the ground or sleeve portion. If pulsating DC passes through there, the little field it creates is in very close proximity to the hot guitar signal, and noise can be induced. 2L man also commented on this.
That is a good point and something that I did not consider.
this could be tested for as peegoo has suggested. Build it both ways.
however, I still doubt it would happen. I think that the ground bus and the ground side of the input Jack all stay at ground potential. the small AC ripple in the DC operating current that flows through the V1 and v2 cathode, will impart a small AC voltage on the cathode resistor, developing across the cathode capacitor. The closest I envision that small AC voltage getting to the input Jack, is the circuit node where the cathode resistor meets the grounded ground bus.
I personally do not see how this small voltage has an opportunity to induce AC onto the signal portion of the input Jack.
If you think that other return current paths exist in that specific (and very common) layout, from the preamp ground bus back to the PT, where are they? Can you identify another path in that example?
like I said above, there are other paths to ground, but I agree with you that you have identified the only direct path to ground with nearly no resistance.