Adam, I had the same problem with one of my AA Transtracs last summer. It ended up being one of the output tubes causing the hiss. Luckily I had some extra tubes to troubleshoot and replace the faulty tube.
Adam, one other thing. The AA amps should be dead quiet. No hiss, no noise just a very slight audible hum with the volume full when your ear is about an inch away from the midwoof.
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.
