I'm contemplating using a pair of 6AU4GT damper diodes for a full-wave
bridge, with a 700 VAC CT tranny.

Yet the spec sheet for the tube has these limits:

Heater positive with respect to cathode:
DC: 100V
DC + Peak: 300V

Heater negative with respect to cathode:
DC: 900V
DC + Peak: 4500V


I assume that during an AC cycle the cathode will "see" -350 volts relative
to the heater which would normally be operating near ground.

Looks like I'd be in trouble without floating the filament at a minus
potential.

Is that a real concern in this application? And if so, is floating the
filament a -300V (using SS rectifiers) a practical work-around?

Else would I be better selecting another device or topology?

TIA,

Jon