100 ohm heater artifical center tap and lead dress question

[wyatt]

I never use the Center Tap because they never measure...well...centered. At least with 2x100-ohm resistors, measured and matched, I know the artificial CT is centered. The nice thing about the CT is you don't lose any heater current to it.

I do occasionally use a 20-turn 200- or 250-ohm trimpot humdinger, though I doubt the need for it so far. Tthe wire runs in an amp are so short, I can't believe they can be uneven enough to unbalance the voltage.

[Cygnus X1]

Dumb Q.
Is there a way to use a diode to prevent cathode current from going back into the chassis ground?

As I mentioned...when I lift the filament using the cathode it injects serious hum from other devices connected to the input.
Difference in ground potential is the cause (I guess).

[pdf64]

when I lift the filament using the cathode it injects serious hum from other devices connected to the input.
Difference in ground potential is the cause (I guess).

I can't see how the ground referencing arrangement of the heater can be the root cause of a ground loop between equipment?
Pete

[martin manning]

As I mentioned...when I lift the filament using the cathode it injects serious hum from other devices connected to the input.
Difference in ground potential is the cause (I guess).

The heater circuit should have one "ground" reference only, that being the power tube cathode in this case. It is isolated from any other ground reference.

[Cygnus X1]

I might have a floating ground then.
I'll check and report back.