Greetings:
I have been collecting single digit vacuum fluorescent display tubes of Russian vintage to make into clocks.
These have a cathode filament voltage of about 0.9-1.5V. The grid cutoff voltage is about -3V, so it's fairly easy to get enough cut off voltage without worrying about having symmetrical AC drive via a CT transformer. Additionally, the low filament voltage vs. the 24-30V anode voltage, makes the luminance gradient unlikely to be perceived and thus not an issue if driven from DC.
The remaining consideration then, for deciding whether to drive the filaments with AC, is lifetime.
Does electro-migration occur and shorten the filament life if driven by DC? Is this effect really significant for a filament that is only at a "dull-orange" heat?
Thanks for reading!