And by fuck, I love it. It's such a fucking brutal amp, and so un-ENGL like. Under the mic, it can get incredibly similar to my 6534+, but a bit more... refined, I guess, and more focused. It can get very ENGL-like if you desire, of course, but for the most part it's just an incredibly polished, huge, tight amp. I wish I could keep it but I'm only borrowing. Doing as many reamps as I can, while I can 
Does anybody happen to know if there's a difference between presence A and presence B, or is it simply there in order to set up two different settings to flick between?

Does anybody happen to know if there's a difference between presence A and presence B, or is it simply there in order to set up two different settings to flick between?