Help with pop and then ground loop

[Intamin]

Ok...so a while ago I moved some stuff around to a different location. It didn't work. I put it all back. I then started getting an occasional static pop, not a hum like a ground loop issue, just an occasional pop. First, I unplugged everything and only had the amp and speakers connected, no pop. I added the preamp, and again no pop. Added my m5, and I got a pop. I used a different cd player to see if it was the source causing the issue, so when I hooked up a new cd player I still got the pop. So then I left the new cd player in, and unplugged the amp. I then connected my stuff to my Rotel amp. I left it on all night, and never heard a pop. I then unplugged the rotel, plugged in the multi 2 to the rotel's spot on the power conditioner, and reconnected everything. Turn it all on, and now I have a ground loop issue. I've also tried running the multi 2 and preamp on a different circuit and the cd player plugged into my conditioner, but that didn't get rid of the occasional pop, and I've tried having all of my 2 channel on a separate circuit, but still had the pop. I also never have a pop when using my HT equipment. So, having tried everything I've tried, where do I go from here? Is it something wrong with the amp that's causing the pop that I could take it in to get repaired? Thoughts? Thanks!