Loud Hum

I recently bought two Brystons 7Bst's to power my Revel Salons. I also have a Bryston 1.7 and I am getting a LOUD hum from ALL speakers (I run the center and rears with a Proceed HPA 3 while I purchase other 7BST's). The Proceed did not make the HUM while I was using it to power the two Salons and center channel, but now that I am using it to power the center and surrounds it is VERY loud. My Revel B 15 ALSO has the HUM (although not so loud).

Any suggtestions?

Thank you!