I'd like to see the schematic of the BHA-1. Is there one floating around somewhere? The Bryston website has schematics for most of their products but the BHA-1 is one that is missing.
BTW, I've listened several times to my BHA-1 used as a pre-amp compared to both my BP-17 and later my BP-26 and always prefer the preamps. I'm not much good at describing how things sound to me but it doesn't take long before I know which I prefer.