Cathode voltage 6L6gc query

[g1]

700 volts seemed too high for the 6L6GC's..

That's in the ballpark of the Musicman 6L6 amps using the same cathode drive arrangement. I would think this amp somewhat of a copy of that, at least the power amp.
See page 4 of attached schematics.

[stephen_G1]

Very interesting, thanks for the information.