I have a new (two week old) Denon 3802. It's been great up until tonight. When I turned it on, the speakers sounded like there was a test tone pattern going to them (all five speakers). I checked and this is happening with any source. Mute works and the noise goes away. Also, turning it all the way down works as well - other than that, volume control does not work and the sound is a constant hum. The unit is performing the video switching properly, and all cables appear to be connected properly. Any advice? Thanks.