AudioQuest RF Stoppers

Has anybody out there tried these little guys? I have a fair amount of tube noise (I think) from my AI L1, but could it be RF from cables? The noise comes equally from both speakers and doesn't increase as I turn up the volume; it's a dull hiss and is constant. I have kimber PBJ's for IC's and python M1 speaker cables. For what it's worth, I also have my DVD player plugged into the preamp "video" channel. Thanks for any help out there, you guys are great. Mark