Hi all, I've got 4 PCC88 tubes (NOS Tesla) which I would like to run in a tube pre-amp that currently uses chinese 6N11's. (Pretty much an ECC88/6922).

They're not actually that bad at all, decent linear sound and very quiet.

I know the heater voltage is 6.3v and 7.0v (sometimes a bit higher) respectively, I just wondered if there was any sort of bridge that could be applied to the circuit to help raise the heater voltage or would it not really be necessary. Tolerances of tubes can be 10% quite easily and although that would be on the edge of whats 'ok', I'd like to give it a shot.

My concern isn't necessarily damaging the tubes but the caps and rest of the preamplifier.

I know SQ may not be as good as it could be if its under-heated, but it may be worth a try if its not going to damage anything.

Thoughts and advice appreciated.