The Codex is a DAC, a headphone amp, and a preamp all rolled into one, packaged up in a small box that can fit right on your desk! Now if you know me well, you know I try to figure out all the different ways to use audio gear, so the Codex turned out to be a real brain teaser. Let's think about this... The most obvious use is as an incredible headphone amp in a desktop situation. You simply connect a good USB cable from your computer to the Codex, tell your computer to send the audio to the Codex, plug in your favorite headphones, and you are all set! The front panel has connections to drive a normal or balanced pair of headphones. In this situation, we are using both the DAC and the headphone amp. To put in perspective just how good this is, I think the Codex is probably equal to if not better than the great sounding Ayre QB-9 DAC and it sports a headphone amp that made Neil Young happy.