Ditto this and what matt said a few posts above. I generally use my odac in my bedside rig, but I have listened to it quite a bit through my modded crack->hd800 as well. It is an excellent little dac.
You just want to make sure it is getting a clean usb signal. The cheap monoprice cable jds includes, with a ferrite choke, works perfectly. When I tried a longer and more expensive cable, without the ferrite bead, there was quite a bit of audible distortion. Bass was also flabby and nothing like what you hear when it is functioning correctly.