What's Your Favorite 6550 for a JCM800?

[FourT6and2]

Yes, it was years ago on this particular amp but I remember being surprised by such a difference.
Btw I also remember finding the difference in sound & feel minimal for such a plate voltage difference, which surprised me too; the amp was less noisy after the recap though (which was the main reason for me to do it in the first place).

Depends where you saw the 40V increase. If all the power amp and preamp voltages went up by 40V across the board, that's a large enough change to feel it in my experience. +40V at the plates, +40V at the PI, +40V at the CF, +40V at V1 node... The amp will absolutely be tighter and brighter, with later onset clipping. If Vp went by 40V but the preamp saw smaller and smaller increases as you go down the B+ rail, that'll yield a smaller change.

I know exactly how much voltage changes affect the sound of the amp because when I build or mod an amp, I use a 5W 50K pot to tune the B+ rail and I can play and adjust the voltages in real time. 40V is significant.

 

[7704A]

I know exactly how much voltage changes affect the sound of the amp because when I build or mod an amp, I use a 5W 50K pot to tune the B+ rail and I can play and adjust the voltages in real time. 40V is significant.

Hey that's pretty nifty, and better than just variacing it to check. Might have to get one.