Rivera Knucklehead - needs biasing when new tubes are installed?

[Traps]

Hello -

I am about to buy the KH-100, old model, I believe from '91. The seller has put new 34's in it, and is telling me that you must bias the amp whenever new tubes are put in, even though they are the same 'type' of tubes the amps always seem. Does this make sense? I thought you only had to re-bias if you changed the type - say 34 to 6L6...

He says the Rivera is NOT fixed/cathode biased, this is why.

Any input? Which is greatly appreciated...

[Big White Tele]

He's right. They must be biased, unless they have the original Rivera labelled tubes, which are numbered, then just relace them with another set of the same from Rivera.

[Traps]

cool, thank you

[jcollins]

Hello -

I am about to buy the KH-100, old model, I believe from '91. The seller has put new 34's in it, and is telling me that you must bias the amp whenever new tubes are put in, even though they are the same 'type' of tubes the amps always seem. Does this make sense? I thought you only had to re-bias if you changed the type - say 34 to 6L6...

He says the Rivera is NOT fixed/cathode biased, this is why.

Any input? Which is greatly appreciated...

He's right about the amp needing bias...He's not right about the fixed/cathode bias thing though. Fixed bias is not the same thing as cathode bias.

[02Singlecut]

Yes....and you can call Paul or Paul Jr. and they will instruct you where and how to....

[Traps]

Appreciate the inputs.