6vdc heaters?

[joesatch]

I'm familiar and have seen 12vdc heaters used but not familiar with running 6vdc heaters (valve wizard describes) off the heater supply. Is this a good idea? If so, why do folks buy transformers for 12vdc heaters?

[uki]

Probably because the type of tubes used in tube amps for guitar and bass, I've on seen only one device using tubes that use 6v, a reel-to-reel recorder.

[pdf64]

DC requires rectification and smoothing, perhaps even regulation. Each of those functions requires heavier duty / beefier parts as the DC current draw increases.
For a given number of active devices, if their heaters are arranged for 6V, they’ll draw twice the current as at 12V.