I just built a subwoofer and bought a used Bryston 4B to power it. (I'm using a Pioneer Elite 45TX receiver). Now, when I power on & off (on the receiver), change inputs and mute, I get a "thump" from my sub. This did not happen with my internally powered Paradigm sub that I had been using. All I did was switch the subwoofer cable from the Paradigm to the Bryston - I made no changes to my receiver. Can anyone help? Is this a problem with the Bryston, or is it something with my receiver, and what can I do? Thanks, Steve V.