Sounds like a faulty unit. Check with Bryston; they'll probably suggest you send it in. Bummer to be without it for a while, but at least you've got the 20 year warranty.
Other possibilities: some kind of impedance mismatch with your preamp or whatever is in the signal path immediately in front (unlikely). Suboptimal setting of the current/voltage switch in the back -- try flicking it the other way and see if the sound improves. Also, it may not be sufficiently broken in (unlikely). Gook luck.
Other possibilities: some kind of impedance mismatch with your preamp or whatever is in the signal path immediately in front (unlikely). Suboptimal setting of the current/voltage switch in the back -- try flicking it the other way and see if the sound improves. Also, it may not be sufficiently broken in (unlikely). Gook luck.