Speaker hum from amp

I have my main speaker outs on my Yamaha 5660 AV receiver connected to a Harman Kardon PM665 amp and I'm getting a hum only when the TV is turned on. I'm using 12 foot gold tip phono connectors and I'm going into the amp through the tape 1 input.
First question, is that the proper input?
I have a phono video cable from the DVD and an RF cable from the VCR connected to the TV. I have disconnected the cables from the TV and left the AC plugged in and I still get a hum. I have run AC to the amp from a different room and still get a hum.
When I turn the amp off the hum stops.
I hope this gives you enough information to help me with this situation. Thanks, Enduser