What Volatge on 66' Bandmaster export model

[David St. Hubbins]

I just got a 1966 Blackface Bandmaster head with the "variac" switch to change the voltage. Preset voltages are 117, 200, 210, 220, 230, and 240. Of course the amp says "for export only" on the back.
What should the switch be set to for best performance here in the US?

Thanks

[Teleologist]

Leave it set on 117 or you risk frying tubes. Setting it to something else does lower the tubes plate voltages, but it also significantly lowers the filament and bias voltages. If the filaments aren't hot enough, you get something known as Cathode striping - the coating on one of the tubes internal elements literally sheds and shortly after the tube shorts or dies.

There's been a lot of confusing articles about people using variacs. EVH for example uses one to get a consistent 120V regardless of what's coming out of the wall socket. Other's who brown out amps that way have full-time amp techs and replacing tubes is not an issue. Hendrix used to use 6550 power tubes in Dual Showman heads and his tech replaced power transformers on a regular basis.

Some amps(Mesa's) have a Variac switch that lowers plate voltages. These are wired up differently and don't affect the filament voltages. Not the same as a true Variac or the Export switching used on other amps.

[David St. Hubbins]

Thanks, thats great info!!!!! I'll leave it at 117....
The tubes get a cool blue glow at that setting also. I'll have to turn my Bandmaster atround when I gig. :hee