Inside a typical one-box CD player there are two main components, the transport that spins the disc and picks up the digital signal and a digital to analog converter for those bits, the DAC. Some players have outputs only for the two channels of the analog signal after it's been converted from digital. Some also have a digital output that gives you access to the signal before it is converted to analog by the DAC.
Some higher-end players also have a digital input that lets you take a digital signal from another source, run it through the DAC inside the player and output a two-channel analog signal.
Narrod is right that you can't use it as a DAC because it doesn't have a digital input but you may be asking if you can use it as a transport for an external DAC. It does have a digital output so if you had an external DAC that was better quality than the one inside the 955 you could go that route for better sonics.