I was getting popping noises on any audio when using the optical audio cable and HDMI. I was previously running it fine with no popping through AV cables. I am running the audio to an Sony STR-DG520 receiver. I was able to fix the popping noise by changing the digital audio input decoding priority on the receiver from auto to PCM. If you have the same receiver it's in menu 5 Audio - DEC. PRI. Hope this helps someone out.