ok ive got a Butler td475 and im getting a repeating popping sound thats very loud and no audio from my source while its popping. the weird thing i am experiencing here is when the amp is turned on and then the speakers are hooked up it is fine but if i hook the speakers up then turn the amp on it goes wild and pops like crazy. i am testing this on a bench so there is no external ground issue as far as i know. anyone have any ieas as to why this is happening?