I'll vote for it being an issue with the 950. This was one of the problems that led me to ultimately return the 950 I had (along with a second one, just in case the first was defective).

I got a loud pop, not limited to the subwoofer, whenever I changed from ANY digital input to ANY analog input. Switching from analog to digital was quiet, just as you described. I never found a solution for this, unfortunately. Too bad, because the 950 performance with a steady input source is really quite impressive!

-Gary