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. The ERC-4 is a great way to get the best sound quality possible from your CDs and from the Red Book CD layer of hybrid SACDs. The heavy-duty transport mechanism handles your discs gently but firmly and the precision DAC in the ERC-4 ensures that you hear every detail and nuance of the music recorded on your discs. And if you have a computer or other digital audio source with a coax or optical digital audio output the digital inputs on the ERC-4 will enable you to upgrade it to deliver the same superb audiophile sound quality.