Rebiasing amps

[errrrrl]

Do you guys rebias your most played amps often? And if so how often?

I recently blew 2 yr old gold lion KT88's in my Ultralead. Finally got a replacement set and checked the bias and it was at 74-77mA. I know its gonna be off since its a different tube set but wasn't expecting it to be that off. I think last time I set the bias it was at 55mA in August 2020.

So it got me thinking maybe it blew cause it needed to be rebiased? Fkrs were only 2 yrs old, not played too much and never really left the house, stationary for the most part. So often do you guys rebias your amps?

 

[Rick Lee]

I check the bias anytime I have the chassis out. But the bias numbers mean nothing without knowing your plate voltage. Dissipation needs to be a function of your plate voltage, not some set number you read in the manual.

 

[BesaMoogie]

Checking Bias more often makes sense with new tubes. Once they are settled in, I assume it`s gonna stay that way.

 

[errrrrl]

Ah... that makes sense. It just got me thinking overall. Most of my amps I never check or retube so was just wondering if I should do like some kind of annual maintenance or something.

@Rick Lee I just use a weber bias rite and set the mA according to what is recommended. So last night someone at Fryette told me between 45 to 55mA. I settled on 52 and it sounds awesome.

 

[midnightlaundry]

Never had a set drift that much except for when I bought from Tube Depot.
Fuck Them. I bought a Quad of KT88's and they were unusable..
Burned in and matched is the way to go.