I am having a problem with hum on Comcast. I had a filter on the input to the STB (Motorola D2007) but that was causing problems receiving some channels after Comcast made some changes (it did work until something at their end changed). I get a really severe hum when using the STB. If I remove the power cord from the STB, I still get the hum. If I remove the audio cables from the STB, it disappears. I'm really frustrated and Comcast is no help. Suggestions?