What effect does tube supply (high) voltage have?

[Frankgb]

Hi,

I'm rebuilding a Matchless Hotbox, but this time I was thinking of using a DC supply from a DIY Valve Mic Preamp.  The Valve Power Supply gives 245v while the older Hotbox one gives 290?

Would there really be any sound difference???

cheers

Frank

[Mike Burgundy]

not really, at those levels.  It does make quite a difference when either the voltage is different enough or you run the tubes low. Below 100VDC things really start to change, because the tube starts operating in a  progressively non-linear region, and dynamics and headroom also suffer.