[infinitesymphony]

Sounds like a broken amplifier. If the sound is distorted, try not to test it too often; it may be sending harmful signals to your speakers. Amplifier clipping is the number one speaker killer.

Try running the receiver's front-channel pre-outs into an input on another receiver (remember to turn up the volume on the Yamaha). This will tell you if the problem is only in the amplifier section of the RX-V850. If the sound is clear, you may still be able to use it as a preamp.