Noisy cable?

I'm trying to isolate where the slight hiss/buzz is coming from after installing some new monster cable to my Bryston 3BST. I've removed the TV coax from the environment, dedicated the circuit to my audio rack...what else could it possibly be? I used the same model cable 5 yrs ago with absolute silence, with a 4BST at the time too.....meantime my audioquest cbl was dead silent when I was using it...anybody know what it could be?