The THX Onyx is a DAC Dongle for Your Headphones

To get the absolute best-quality audio you can between your device and your headphones, the Onyx DAC from THX makes it easy. This tiny USB dongle plugs in to deliver clean DAC with 4 options for sound: standard, high resolution, Direct Stream Digital (DSD) and Master Quality Authenticated (MQA). Works with PC, Mac, Android & iPad.