I don't think it is a biasing issue. I have run my SV above 35mv for a while. Try doing the pencil test. Tap lightly on all your valves with a pencil and see if any of them are noisy through the speakers. I find some power tubes make a difference in tone. The Tung-Sol 6L6GC that i tried out were very bright compared to JJ's or Mesa 6L6's. Could be the AX7's you have in there as well. My amp has always sounded harsh in the treble. try cutting back some of the mids as well, you might be able to turn up the treble that way. One way for sure is turn the presence down. IMHO the presence is unusable above 12:00 O'Clock. Most of the settings i use have the treble almost backed all the way off with the exception of the cleaner tones i use. The treble needs to be up a little to cut it in the mix if your jamming. Maybe try some different power tubes? It is possible those valves have prematurely gone bad on you. Good luck. Cheers.