Audioengine D1 Premium 24-Bit DAC (digital-to-analog converter) means that you can bypass your computer&0s soundcard or headphone output & send audio through USB (Universal Serial Bus) or optical to listen to on your active speakers, hi-fi system or through headphones. The obvious choice of active speakers are of course either the Audioengine A2 or Audioengine A5+ but you can connect the D1 DAC to any music system with an audio input. The D1 will improve the sound of all your music stored on your computer!