I am currently using it with the iMac's optical out, as well as with the front plug when using my excellent NVX Audio XPT100 headphones - the downside is that there is absolutely no configuration possible via the Audio MIDI Setup app, and no volume control (since all of this is handled directly by the DAC). I am interested in using it with my ALAC music collection, as well as increasingly HD-grade music. So my question is: should I connect the DAC with USB instead of optical? Can I use optical for the sound and USB for the configuration? Which one normally provides the best/cleanest audio connection? I am really new to audiophile-related discussions and would welcome any expert advice out there...thanks.