Nothing unusual. My 558.2 hums on saturday mornings and the 559 is completely silent. ive just got used to it but if anyone knows of a fix, i`ll try it.

G98, HD621, 568.25, 558.2, 559, B&W 803Ds, HTM2D, 4xSCM1, ASW850, Pioneer PDLX5090 50" Plasma, Cables by Atlas and Chord