Pre-amplifer for magnetic phono pick-up.

[ppppenguin]

Sounds like a job for a couple of transistors or an opamp. Power either from the heater supply or even dropped from the HT with a zener to stabilise it. Apart from lower noise and hum, another advantage of solid state is less loading on the mains transformer.

If you must use a valve then look at the Quad 22, or Leak/Radford/Rogers designs of the 1960s.