Treble Grain? How to Eliminate?

I've had a DacMagic for about a year now, using it mostly with USB input. I recently began using it in a headphone system and am noticing that this dac exhibits a high amount of grain in the treble. It makes for some heavy listening fatigue. Is there anything I can do to improve this? What other dacs under $1000 have a notably smooth treble?

Thanks