Well I don't believe it, but I disconnected the house cable line, and the noise went away. This line goes to a 4way splitter which supplies the TV, TiVo, and VCR/DVD.
I believe the splitter has a DC pass through.
I reconnected the house cable with none of the devices connected, and then reconnected seperately to determine which device was the source. Unfortunately when any single device is connected the noise returns.
When I do any of the following the hum goes away.
1-AC ground video splitter.
2-House cable through Panamax coax Isolation line.
3-AC ground denon chassis. (not a good solution)
4-drive front speakers with denon only.
For items 1 thru 3 there is a very very low level high frequency noise almost impossible to hear.
I'm wondering are items 1 & 2 good solutions, and what should I do about the residual noise?
Please note the TiVo, Wii, Playstation, and xbox go to a Philips AV switch that outputs to a 720 upconverter, which than supplies an hdmi signal to the TV. The TV supplies a digital audio to the denon reciever. Not sure if that helps.