kt77 plate volt question

[Luthierwnc]

I have a power trannie that should put about 475VDC on the plates. Is that too hot for the sweet spot on an HRM using JJ KT77's

Thanks, Skip

[phsyconoodler]

That should not be an issue.You will just have to adjust the bias accordingly.I like KT's in my amp a lot and they sound great for all sounds.The voltages just give a slight bit more clean headroom.

[Trace]

Generally speaking; The screens tend to be more sensitive than the plates regarding higher voltages. A word of caution - if the KT77's are JJ's I would make sure they are burned-in before using them, otherwise the chances of them shorting prematurely are greatly increased (unless they are 2-3 years old).


Hope it helps
Trace

[Luthierwnc]

Caution appreciated. A friend of mine and I both had JJ 7591's red-plate within a month of each other on stage. One minute they were fine and the next we were scrambling for a spare amp. Up until then I thought I could take them for granted. sh