Ok, I unhooked the interconnect from the amp and put my ear up to the tweeter and still there is a slight hiss. I'm guessing then, it is from the amp. This baffles me though from reading Gonk's review of the 990 he mentions no hiss at all and he's using the 750 amp. I would expect the noise floor to be the same between the 7100 and 750 amp? Hopefully Gonk will chime in here....