Manual vs. Auto Bias

Marakanetz,
Thanks for bringing up that point. The builder of my Coincident amp as I recall did mention soft startup for the tubes in this design, and said tube life is very long.

More over I'd say that if I ever go back to tubes, I'll make sure I'll buy an auto-bias amp or if price is convincably low for fixed-bias unit, I'll DIY implement it(most-likely with SS parts for less space and money).

Not sure why the discussion of auto bias vs. fixed has come about since the OP is seeking info on auto vs. manual bias, where neither is fixed. Anyway, my manual bias amps also have the soft-start feature, which certainly is good to save tube life.

Manual bias adjustments here with a 2 minute soft start (Lamm ML2.1).

Need a decent true RMS voltage meter (I use a Fluke) and one has to make adjustments to both plate voltage and current on each monoblock. The measuring jacks and adjustment pots are right on the top, with the required values written adjacent - very easy access. It's a ten minute job and the drift over time is small. It's not a problem.

Regards,

Tube auto bias circuits are SO cool...I wish they had 'em in guitar amps. They get rid of an issue I've always had with high end tube amps.