Input and concertina Phase splitter

[acorn]

Hi all

I have been reading Morgan Jones notes on his amp using a ECC88 for input and the concertina driver stage. He said that because there is insufficent voltage you cannot use a 6sn7 type valves, the sn7 family needs more HT, but there is 285 volts availabe ? and he is using 187 volts on the anode of the concertina and half that on the cathode.

I dont quite understand that because I thought these valves were quite happy running at lower voltages, am I missing something here

Regards Acorn