I have a NAD T753. When i put in bourne ultimatum in my toshiba hda20, and it loaded, when my nad jumped back and forth between the digital source, it made a loud pop sound. It has done this now a few times with different dvd's. I'm not sure if it's something wrong with the digital automatic switching in the receiver or not unless for some odd reason it's the dvd player. Also with my dish network vip622dvr, when listening to different programs there will be an occasional popping sound randomly. I hope someone here can enlighten me with what might be wrong. It's starting to become a nuisance. Thanks.