hey there - got this GenzBenz Intro 90 amp today, mailed to me. looks fantastic and even sounds pretty good - but there's a small problem I wonder if you guys can help me with. Anytime I plug anything into it, it buzzes like a bastard - like 60 Hz AC hum, only it's just the high pitched part, coming thru the tweeter. I've tried every cable I can find, and it's only when something (a jack or even a finger) is touching the tip of the opposite cable end. Now, I'm not going to expect a refund from the guy or anything silly like that, just wondering if somebody can help me track down the issue - anybody knowledgeable in amps specifically? thanks for any assistance!