Wessel Dirksen wrote:

I just thought of something which has to do with the above post.

Obviously I have been adjusting bias of the power tubes at every step
which made me realize the following (kinda like Homer Simpson . . .Doh)
. As in bias adjustment in power tubes, it is probably better to match
measured current (voltage over Rk) than B+ potential. True?

It is elementary dear Wessel, to match currents in tubes where
appropriate.

Both channels in your system should have the same B+ voltage and same
idle current in the tubes at the same circuit points for each tube.

The gains should then be equal, but may not be, especially if no
applied loops of NFB are used, and if this is the case,
tubes with the same gains should be chosen for your amps.
This isn't so hard, as medium µ triodes which are new, and
from the same maker are usually with a couple of percent.

For perfect balance, some sort of resistance divider can be placed
judiciously so that gains can be trimmed until equal.

Patrick Turner.