Under load, batteries aren't completely quiet either, although the noise is higher frequency. I would still recommend filtering caps. I lost some links on the last computer crash but I read somewhere that one of those "super regulators" combined with an IE-core tranny outperformed a typical sealed battery for noise. Batteries do have the advantage of nearly instant speed and huge current to handle transients.
Tube amps typically have over 90 volt rails so many batteries would have to be in serial.
Tube amps typically have over 90 volt rails so many batteries would have to be in serial.