1 or 2 bias pot?

[sergio]

In an amp with 4 tubes is better use 2 bias pot for a fine adjustment and balance two pair tube?
Thanks

[LooseChange]

Any way to individually control the bias on your power tubes is better than one universal control.

The best would be a pot for each tube. Have you ever played an amp with a pair each of 6L6's and 6V6's? How about four unmatched NOS RCA? EL34's and 6550's? One each of each type listed above?

[Luthierwnc]

With 4 tubes you can usually mix and match to get the sides tolerably balanced. sh

[Firestorm]

The data sheets for KT66, KT88, etc. say that it is "essential" to have a separately adjustable bias supply for each tube. Of course, they say a lot of other stuff that we ignore ...

[llemtt]

Balancing currents in the two halves of the OT is very important when max headroom and bandwidth is mandatory: for instance bass amps!

In a guitar amp isn't always a good idea unless you do balance also the PI levels to preserve symmetrical clipping of the output tubes.

teo

[sergio]

Well , there are different ideas about this.