That dreaded hum

Hello all, I hope I'm in the right place and my question is what can I do to get rid of a ground loop hum in my rig. The particulars: I have my audio and video hooked together and when I want to watch dvds I have to disconnect my cable from the wall to eliminate the hum. I know Mondial used to make a box for this problem but that was many moons ago. I thank you in advance and happy Memorial day.