I just a got a used Crest CA9 power amp and it can't be within a foot (literally) of my old Alembic F2B preamp without emitting a subtle hum that gets louder as I turn up the power amp up. (I didn't have this problem with my QSC PLX.) If I turn off the F2B or move it to the side of the CA-9, the hum dissapears...and the tone is awesome. I guess they won't be sharing a rack together anytime soon, but it's a bit inconvenient. Not too big of a deal since the CA9 deserves it's own 2-space rack due to its weight. Maybe this is just a bedroom volume issue....I don't know. Anybody have any thoughts on how best to shield the F2B? Or, do I just get longer cables and put the CA9 on it's side next to the cab or something? Is this an issue with other tube pre+"lead sled" power amps? Thanks!