Apple TV and Brightness

I recently purchased a new Apple TV gen 2 and have ripped a lot of my Cd collection into iTunes in WAV format and have it running to an external DA converter using an 'acoustic research' toslink. It was the only toslink I had lying around from their 'master series'.

After doing several A/B comparisons back and forth between dedicated transport (using a Moray James digital interconnect) and the Apple TV I was under the impression there was very little if no difference. In fact I thought the Apple sounded better in some respects.

Fast forward a few days later and I've noticed a thinness to the sound, the high frequencies are there but it's rather harsh, almost like it's shouting at me and not as even keeled. The bass seems to be leaner as well. Am I realizing I made a mistake or perhaps through cabling can I tone things down a little bit?

Any suggestions? Would a different toslink help? Another crazy idea I had was to get an Audioquest NPR power cable for the apple TV? Are there any gains to be had based on personal experience?