Thanks for the answer, I hear you concerning taking off the top cover. It's just that I have exactly the same problem with both my Evo's for a couple of months now after working fine in thebeginning; also when I touched the top cover or ls-cables the hum diminished. So I tried swapping everything there is to swap (cables, chords, different group panelboard, etc.). I brought them both three times to two different repairshops, twice of which to the official service repairhandler of NuPrime here. They couldn't find anything wrong; it just worked fine over there. Just after they came back from the repairshop they worked fine here too but after a while the hum came back and I couldn't get rid of it. The Evo's are only about two years of age but I bought them secondhand so there's no official guarantee anymore. Reading the story of sresener gave me hope that there is a "simple" fix by replacing the "amp board". Or are there also other known causes for the hum?