What am I hearing from this amp?

I recently bought an Anthem MCA5 series II amp to add to my Integra 8.2 receiver and Kef ref 2~2 speakers. With the receiver connected to the speakers,the speakers are dead quiet with any setting on the volume knob. I added the amp from the pre-outs of the receiver with my 5 speakers hooked to it. At -55db from the right front channel I could hear a slight hiss 9" away from the Uni-Q driver(mid and high). I could hear a quieter hiss from the left front channel. All other channels were dead quiet. I unplugged all the interconnects leaving the speakers hooked to the amp. I then heard what sounded like air moving from the same speakers, but the hiss was gone. I could switch the spkr connects and the sound would move to whatever was connected to the front right and left channel. Is this a ground loop hum? or something else?
The amp went to Anthem and they say nothings wrong with it. Any suggestions or thoughts would be appreciated.

Mark