A CD player is an electronic device that plays audio compact discs. Modern units can play other formats in addition to PCM audio coding used in CDs.
DACs are commonly used in music players to convert digital data streams into analogue audio signals. The are digital to analog converters, and there are several DAC architectures; and there have been several phases of evolution in their design as digital recording has contiunued to increase its resolution.
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A CD transport is responsible for reading the transcribed audio information on the compact disc with a special laser and that is transferred back to a sophisticated series of electronics and that digital signal is converted into an analog signal for playback. Transports are often CD players but can also be a primary drive.