I just got a pair of Sony MDR-NC20 headphones. The noise canceling feature works much better than I was expecting. Although I have yet to try them on an airplane, it does a great job of blocking the window A/C unit near my desk at work.

Here's the "problem" -- while at work I plug the empeg in with the AC adapter and attach the headphones to the back of the empeg (MK2A) using a stereo RCA to 1/8" stereo miniplug adapter. With these new headphones I hear a very low hum when the player is paused and during quite periods of songs. This does not occur if --
(a) the noise canceling circuitry is turned off,
(b) the headphones are detached from the empeg, or
(c) other non-NC headphones are attached.

One more "clue" ... if I touch the metal housing of the empeg the hum totally disappers (it sounds perfect) until I stop touching it. Is this some sort of ground loop? I welcome any suggestions on what I should do to correct this (short of keeping my hand on the empeg at all times). Does anyone else have these same headphones, and if so do they experience the same problem? Thanks in advance. ...Mark