I have just set up a brand new Denon AVR 990 receiver. Beautiful sound but found an unusual problem. While playing a source using the receiver's Direct and Pure Direct settings I get loud popping and crackling sound from the front left channel. I have checked speaker connections, dvd/cd player connections and settings, changed digital connections between player and receiver, and have tried a different dvd player. It only occurs in the left channel, not on the right. I also switched speaker connections, still noise only from left channel. Anyone ever encounter this issue?