audio problem with my AES

hi all, i have a revision 3-6 model AES (200,000+ serial) and there is loud noise/static interference with the sound, especially when there is any deep base to the sound effects/music. It's the same through MONO out of the back or the Stereo at the front. is this a common problem or a bad issue? maybe the connection isn't grounded properly or something but i have no idea.