I currently have a bellari vp130 hooked up to my MF 5.1. When I turn on my amp the speakers visibly oscillate at a low frequency that gradually speeds up. This occurs when my turntable is off. I am able to get rid of the noise by hitting the mute button on my phono amp or by pressing the rumble filter button on the phono amp. It seems that the problem is the phono amp. Could this be due to an old tube? Anybody experience similar issues?