Just thought i would throw this out, the amp has a small fan located in the back.
on 90% of them, there's issue with the motor being slightly out of balance and causing the internal metal case to vibrate. it's a 12V/DC brushless motor, unsure of the size that you can replace fairly easily if you absolutely have to have it. I ended up placing the amp in the closet behind me and running the wires through the wall to avoid the noise.