Not sure how to deal with this, but it's driving me crazy. My Series 3 is in a wood cabinet, sitting on top of a Series 2. It emits a really, really annoying low frequency humming sound, that is cyclical in nature. HUMMMMMMhummmmm_________hummmmmmHUMMMMMMhummmmm and so on one cycle is roughly 5 seconds long. At first I couldn't even locate it, because it's not a very directional sound. It is also enhanced by the cabinet, which seems to work as a resonance box for it (it still makes the humming noise though when I pick it up). I have no idea how to deal with this, and I don't know what causes it, but it's really, really starting to annoy me. It also resonates throughout the house (which is very small), so I can't escape it... Anyone experienced it? Know how to fix it?