Mattheus,
It's indeed most likely an AC problem, but probably otherwise then is stated before. I've had the same thing occuring with my auditioning of an AA Capitole mkII. In my case I had the AAC correctly plugged in my MIT Z-center (wich is very important with AAC), but my poweramp in the wrong way. Indeed pain in my poor ears! First I also tried other cables, but this didn't chanched anything of course. Everything plain on the mains, that was the moment I discovered my mistake with the poweramp.
So check if the rest is connected in phase on the main.
Good luck, Edzard