(02-26-2016, 12:29 PM)Hangman Wrote: Here is my opinion: I don't think most of this is particularly necessary. Ampeg biases these amps pretty cold (around 60% max plate dissipation), and they actually sound good that way. I have tried biasing them hotter, but they get pretty muddy and lose definition.
I second this, just for the record. Also, below 60% doesn't sound bad at all either! I think I prefer it lower, personally, but that is just me. Plenty of mids can be dialed in (or out) on this amp, unlike most other tube amps. It's fenders or marshalls or voxes, where the bias becomes a tonal thing that's useful. Here, hot bias just isn't needed, especially if you run the amp relatively clean (and maybe beyond).
There's nothing quite like the big fat lows this amp provides, though, and those shine best and most defined at 'cool' bias, which in this amp, is relative, as the plate and screen voltages are far from 'cold/cool' given the tubes specified.