What Is the Purpose of the S/PDIF Port?


Computers and DVD/CD players come with ports for many things. Some of these input and output devices seem mysterious until you know what cable goes where and what it hooks into. The S/PDIF port is one of the output devices whose function is not readily apparent by the name or label on your computer, but it serves a purpose: to get audio from your computer or other player to your home theater and speakers.

Basic Function

  • S/PDIF stands for "Sony/Phillips Digital Interface." The S/PDIF port allows you to transfer digital sound to an amplifier or television. It can play PDM and Dolby Digital audio and is not restricted by file type or sampling rate. The sampling rate of an audio track is how many samples per second the track has. Samples are the bits of data that contain the audio track when they are put together. S/PDIF can handle various sampling rates to get quality sound to your television speakers or an amplifier.

What it Looks Like

  • The audio port for S/PDIF is round and is often colored orange. It may be labeled "S/PDIF," "Digital Audio Out," or "Coaxial." The cord is an unbalanced coaxial cable. It has a conductive core, an insulating layer around that, another layer of conductive copper, and then a final layer of insulation. Unbalanced means that the two conductive layers transfer electric signals differently and are connected to something that is grounded. The cord is round with a male plug for the S/PDIF port resembling the plugs for many game systems: a silver cylinder with a blunt, rounded tip. These are called RCA connectors. The cords are usually black with silver plugs.

Optional Toslink

  • You can also use the S/PDIF port with an optical cord rather than coaxial. Optical cords transfer signals from light using plastic or glass fibers, rather than the copper used with electrical signals. This is provided by a Toshiba Link, or Toslink. It is a somewhat rectangular port labeled "Optical" under the Digital Output. It has a plug to protect the red laser inside when it is not in use. This cord is also often black and silver.

Professional Version

  • The S/PDIF port is meant for home use. A version is available for professional use with higher signal voltage. This is called the AES/EBU. This does not have an optical version, and the port and cord look different. The S/PDIF equivalent is the AES3id. The port is a silver cylinder with a pin, and the cord has a slot for the pin to go in. There is a version with even higher signal voltage that does not utilize coaxial cables, called AES3. Conversion between home S/PDIF and any AES/EBU needs to be done with electric circuits and not adapters.

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