You're correct, the cable box and modem have no ground prong on their plugs. Your suggestion is supported by my observation that when I attach the ground breaker, or unplug the coax from the wall jack, the humming decreases. What is a ground loop problem? Are there any solutions? Thanks for the advice.
RF Induced Humming??
I have cable TV and cable modem on one line. I can hear a humming sound coming from my speakers when my amp is on and nothing is being played. When I add a ground breaker to the cable coax at the jack in the wall the humming dissappears, but then I lose reception in my local TV stations and my cable modem loses connection. Does anyone have any solutions to this? Thanks.