Did you ever resolve this? I have this going on for years as well.. I just bought a new PC and moved my XFI to it and it's the same thing all over again. This time it's Windows 10 and not 7 like before. I'm connected via optical out to my Logitech Z-5500.. As soon as sounds starts it pops loudly and then plays fine. The only thing I was able to do to "kinda" prevent it is to play some audio file on the loops with 0 volume then it doesn't pop because it thinks that sound is already "started".. soooo annoying..