The Emotiva ERC-4 Differential Reference™ CD Player and Digital Transport combines a high-quality digital CD transport and a superb balanced DAC (digital-to-analog converter) in one convenient and attractive package. In addition to serving as an audiophile CD player and transport, the ERC-4 offers both Coaxial and Optical (Toslink) S/PDIF digital audio inputs, so you can also use it as a DAC with any of your other digital audio sources that includes a coaxial or optical output.