I have 2 Parasound amps which power my back four speakers in my HT; they are each 125 x 2 ; the side speakers hum appreciably; the back ones hum alot less, but still present; I have 500$ power cords in each; a recently purchased noise harvester from PsAudio.
Is this the famous "ground Loop" problem or is this a problem with the amp ?? Thanks. JCB
PS My Parasound 200 x 3 amp (fronts) does not hum at all.
Sounds like it to me. If the amps have balanced inputs, use them. If not, start by disconnecting any coax for cable or sat. If this stops the hum you need a ground break or try a cheater plug on the amps.

Try a cheater plug on the amps. Best 63 cents I ever spent.
I found Parasound amps to be incredibly susceptible to ground loop. Try the cheater plug as suggested above, unless your power cords have removable ground plugs, in which case . . .
I assume you have the HCA-1000? There is a ground lift switch on the back. Flip this switch and you have just done the same thing as using a cheater plug.

Good luck!