Liverpool bias (going down!)

[Reeltarded]

Amp is with 6P14P-EV. I think they need a little less push.

[Mark]

Amp is with 6P14P-EV. I think they need a little less push.

You can reduce the 68K resistor to 56K but you lose that craziness. You could try an 12AT7 in the P.I. to reduce drive to the output stage. I’m not sure biasing the valves cooler will result in forward conduction happening significantly later.

[Littlewyan]

… some cathode biased class AB amps are specced at 80%ish idle bias, some even biased cold at 55% and some at max dissipation. …

Bear in mind that bias can be tweaked to operate closer to class A. But another approach is to increase the load impedance. Might that align with the 55% example?
It’s about conduction angle, and the change in current from idle to max output, rather than idle dissipation per se.

I now remember! The 55% idle dissipation was to get a similar distortion level to a fixed bias set up and it was with an ultra linear set up.
And you're right, I think in a 5881 datasheet they give examples of both fixed and cathode bias, in the cathode bias they always bump the load impedance up a tad.

[Littlewyan]

If less drive is the intended outcome then I would have an actual voltage divider between stages 2 and 3 to bring it down a tad, whilst adjusting the coupling capacitor at the same time if needed to keep the bass cut the same.