The lower Va (anode voltage) the lower Vh (heater voltage)?

Quite possibly so.


It can be seen on all electron tube textbooks, cathode temperature vs anode voltage curves, for example for diodes.


Would it be possible to operate an EF98 or EF97 with just 1.5 volts for both the heater and anode circuit? On a Pleiades V6 configuration?


Or is the EF183 triode connected the best electron tube on the planet?


Reference:


Pleiades V6 schematic