We have a Dell Dimension 4700.  About 2 years ago, we had our computer audio output connected to our Denon DRA 295 Stereo Receiver.  The receiver is also connected to a Denon CD player and tape player.  The receiver in turn is connected to speakers in several rooms of our house.  All of wiring and connections were handled by a local audio store and everything has been working fine until yesterday.

We often listen to Internet radio and of course, play this through the Denon receiver.  Beginning yesterday, we now have a low hum through the speakers when running the Internet radio option.  I've tried the other options, radio via the receiver, the CD player and tape player and no hum from these sources.  This tells me the computer is causing the hum.  I did check the plug at the back of the computer and it is seated properly.  Could this be a problem with the computer sound card or what????

john