the cables could make a difference. i switched from plastic to glass toslink from my apple tv's or airport express units and there was a difference. i also go to a jitter device between the apple tv and the dac. another big improvement over going directly from the atv to the dac.
Apple TV sound quality as a transport
I recently switched from a DVD Changer into a Channel Island DAC to an Apple TV into the same DAC. I was under the impression that the DAC was ultimately responsible for the sound but I swear it actually sounds better. The only change other than the Apple TV is the switch from coaxial from the DVD to optical from the ATV. Is it possible that the ATV sounds better than my DVD changer as a transport?