A CD player is an audio component designed to play music stored on compact discs. It uses a laser to read digital information from the disc and processes this data to produce an audio signal that can be sent to an amplifier and ultimately reproduced through loudspeakers.

A standard audio CD stores music digitally using two-channel PCM audio with a sample rate of 44.1 kHz and a bit depth of 16 bits. This means the audio is represented by a sequence of numerical samples rather than the physical groove used to store an analogue signal on a vinyl record.

When a CD is inserted into the player, a motor rotates the disc while an optical system directs a laser onto its surface. The player detects variations in the reflected laser light and uses this information to recover the digital data encoded on the disc.

The digital information then passes through the player's electronic circuitry where errors are detected and corrected and the audio data is prepared for playback. In a conventional CD player, an internal digital-to-analogue converter, or DAC, converts the digital information into an analogue electrical signal.

This analogue signal can be sent from the CD player's RCA or XLR outputs to an integrated amplifier or preamplifier. The amplifier increases the signal to the level required to drive the loudspeakers.

Many CD players also provide digital outputs such as coaxial or optical TOSLINK. These allow the digital audio signal to be sent to an external DAC or an amplifier with its own digital-to-analogue converter. When used in this way, the external device performs the digital-to-analogue conversion instead of the CD player's internal DAC.

A device designed primarily to read a CD and provide a digital output without performing digital-to-analogue conversion is generally known as a CD transport. A transport therefore requires an external DAC or another component containing a suitable DAC before the signal can be reproduced as analogue audio.

CD players can differ considerably in their construction and features. Differences may include the disc-loading mechanism, power supply, DAC design, analogue output stage and the range of digital connections provided.

Despite the growth of music streaming and downloadable digital audio, CD players remain an important source component for listeners with compact disc collections. They provide a straightforward way to play physical digital media and can be used either as complete audio sources or alongside external digital-to-analogue conversion equipment.