• 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.

Pioneer SM83 and 500k pot

I have a pioneer sm83 amplifier which has a 500k dual gang pot. It is rather dirty despite cleaning but finding a new high quality pot that meets this spec seems difficult most seem to stop at 250k. The amp has ECC83 preamp valves and 220k biasing the anode should I change this value as well?

Any thoughts on the best make of new 2 gang pots for valve amps in general