Both of my Aragon 4004 have transformer noise. My old Adcom 5802 had the same problem but Emotiva filter cured it. More of a humming roar, varying up and down in volume. Read on forums that it is due to DC offset on my AC line. Measuring about 160 mV max. Tried a few DC line filters (not sure if I should name manufacturers here). Most had no effect, one had eliminated the noise, but sound became totally dead and cold - also a phenomenon described on forums. Has anybody been able to solve this problem? Isolation transformer perhaps? Live with noise? Switch to different amps? Move to another apartment? Or city?