OK, I'm back. Sorry to hijack the hiss discussion. Yes I was using a UL310, epic fail. Really awful with a P bass(rounds), tolerable with a Jazz(also rounds). Switched to my trusty old Goliath cab the other night, much better. But still too much upper mids happening. I'm on the road till Friday and can't try anything till then, but if you have suggestions, please suggest.
I've been trying to use the head 'flat' for the most part, with Gain at 1 o'clock, a slight Bass bump(1 o'clock), Mid cut(11 o'clock) and treble at 12 o'clock, or slightly less. Voice at setting 3('flat'). I have tried the number 2 filter setting but felt it took away too much 'punchiness', whatever that means to you. To me it means 400hz or so, the control is centered at 540hz. The Mid knob doesn't reduce the offending frequencies without taking other stuff with it.
Maybe there is an odd (to me) way of dialing in a better sound, like Chef was talking about defeating the Hi Pass filter by pulling the bass knob, then reducing bass, etc...I want to work with it some more if I can. It is a nice piece, if I can make it work. The power/size/weight combo is unbeatable, which is why I bought it. But that 900hz bump has me stumped. No obvious way to reduce it that I can see, and a P bass is already really strong in that region, so....?
For an idea of where I'm coming from, I really, really, REALLY like the sound of my Demeter HPB-1 /power amp sled. Got the M6 to reduce the schlep factor.