Power Tube load sharing

[g1]

He didn't think matching tubes was a thing, or even from side to side on a Twin as far as I know.

The later SF Twins etc. did have the 'output tubes matching' trim pot, but it was all about nulling audible hum, not balancing power output (or symmetrical clipping).
Modern Fender's no longer have this, but they come equipped with matched power tubes, so excess hum due to mis-match is not an issue.

[Helmholtz]

The later SF Twins etc. did have the 'output tubes matching' trim pot, but it was all about nulling audible hum, not balancing power output (or symmetrical clipping).

Not so sure about the last part, as minimum power stage hum is a consequence of equal gain on both sides of the primary, which typically means balancing.

[Enzo]

Equal gain? Or equal idle current?

[Helmholtz]

Equal gain? Or equal idle current?

Equal gain (at idle) I think, but might be wrong.
Hum cancelling requires AC currents through both primary halves to be identical (and in-phase).
I'm not sure if equal DC currents can ensure that with somewhat different tubes.

With similar tubes, equal gain at idle typically (though not always exactly) goes along with equal idle currents.

Neither equal gain nor equal idle currents ensures symmetrical clipping, but chances are good, if tube characteristics
- especially saturation voltages - don't differ much.

[g1]

Well a bit of 'chicken or egg first' scenario then. The instructions were to adjust for minimum hum. Maybe that was actually the goal, or maybe they thought it was the simplest way to get to symmetrical clipping.

[Helmholtz]

Well a bit of 'chicken or egg first' scenario then. The instructions were to adjust for minimum hum. Maybe that was actually the goal, or maybe they thought it was the simplest way to get to symmetrical clipping.

What I meant say is, that I think it's both "chicken and egg"".

Adjusting for least hum allows any untrained user to get decent balancing without using a meter.