what are you using as a pre/pro? Do you use coax or optical for digital sound hookup? Have you disconnected you TV/Sat cable from the tv to see if its solved? Do you have a cable/sat box hooked to your pre/pro via coax for audio? Switch to optical.
WHen my directv is hooked directly to the TV i get no hum, when i hook it up and turn on the parasound amp i get a hum. as soon as the amp is off nothing. All of ym equipment is 2 pronged where my Parasound is 3.
Are your DVD and direct TV hooked up via coax or optical to you pre/pro/receiver? Try connecting all via optical. If you have a sub see if unplugging the sub coax cable helps. If you have a surge protector try running your direct tv coax cable into the surge protector then to the tv. This may ground it. Or if your pre/pro/receiver has a FM tuner hookup that accepts tv cable run a piece from it to your surge protector. And before you try any of the above try running a piece of wire from your amp to pre/pro/receiver to see if you can ground them together. Use a screw on the casing of the units to attach the wires too.
I never had a problem with the video being hooked up it was just the digital coax. When I replace them with optical, the hum disappeared. If you still get the hum even after replacing with opticals try:
1. Removing Sub coax cable hooked to receiver/prepro 2. Try grounding the amp to receiver/prepro buy connecting a piece of wire between the two. Use screws on the casing. 3. If you have a surge protector with coax hookups run some cable from your sat to the surge then back to your tv. Or if your receiver/prepro has a FM tunner hookup on back that accepts TV cable run a piece from it to the surge protector.
Hopefully one of these solutions will ground your setup. For me it was running the cable from my receiver to the surge protector.
Try one of these. Model VRD-1FF. I just ordered one. Several people on the sound and vision forum have resolved that same issue with it. I ran my Satelite and Cable coaxals through my Power Conditioners which reduced the hum significantly. The problem I have left is the noise shows up in my video as a faint rolling scanline/pixel. It too was resolved for someone on the other forum after using the Model VRD-1FF. You can find it at http://www.jensen-transformers.com/iso_vid.html It's an in line transformer.
I'll let you know how it works out for me as well.
I also have a ground loop hum caused by my cable and I recently bought one of the Dayton video isolation transformers from Parts Express to solve the problem. While it did solove the hum problem, it doesn't pass through the entire digital cable signal without degrading it somewhat. A few of the digital cable channels are unwatachable, and it loses the signal momentarily quite often with some of the HD channels (on a Motorola 6412 DVR). I noticed after looking at the specs the Dayton transformer operates in the 100MHZ to 1000MHZ range, while the Jensen VRD-1FF operates in the 2MHZ to 1300MHZ. I just ordered the Jensen VRD-1FF and I'm hoping that it will solve the hum problem with no side effects. Unfortunately it's 5x the cost of the Dayton transformer. I will post again once I have received it.