WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
I stock Russian made 6n3p-E (ECC42) and 6n1P (ECC88). Low noise double triodes of similar specification with pin 9 as a screen (not heater centre tap as in ECC83 etc).
Fairly inexpensive too!