First off, I love this setup - it sounds accurate and great, and powers anything. No, it's not "high-end", but for those of us on a teacher's budget, it's perfect.
I just traded in my MacBook Air for a new iMac, and now I'm hearing a humming and buzzing out of my right ear. This didn't happen with the MacBook Air - well, I shouldn't say "didn't", but it only happened when I was too close to my external monitor.
I have a good USB cable with a ferrite bead, and very good Monoprice RCA cables (short ones) connecting them together. I notice that the humming/buzzing goes away after about five minutes of the unit being on, although it does NOT go away if they're on different power strips/surge protectors. Very strange.
Do I need a new USB cable, maybe? Would that help? I've tried plugging it in to different things - different ports on the computer, a USB hub, etc. I just can't figure it out, except that it must be USB cable related.