I'd say it would be pretty pointless to use batteries for filaments. As long as we're not talking directly heated tubes you might as well use AC. It makes no difference. Having a constant temperature is far more important than how clean the power is to an indirectly heated tube.
Dc for power supply
Anyone use 12v or 24v car battery as dc power supply for home audio. Or even for filament on tubes. I like to know if any members try different types of battery. Lithium, Lead Acid, NiMH, Agm, Gel etc... Can you tell me if it makes a huge differences on each type of battery. I like to use it to run my dc filament on a cd player. Please advise??