S / PDIF audio connection, what it is and what it is for

SPDIF audio connection, what it is and what it is for

SPDIF is an audio connection that we can find in many devices, although its use is less and less common because it has been overtaken by other interfaces, for example the HDMI port and the DisplayPort. In this article we explain what the S / PDIF connection is, what its advantages and what it is for .

S / PDIF is a digital audio interface that was developed jointly by Sony and Philips. It is a port that is only capable of transmitting audio, so it is not suitable for devices that also use video. An advantage of using S / PDIF is that it transmits audio digitally, so the final quality is higher than analog devices. Digital signals are not affected by noise and interference caused by other nearby devices.

The characteristics of S / PDIF

In what situations can using the S / PDIF interface be useful? In the event that we have audio devices that do not include an HDMI or DisplayPort port . Some examples of these devices are professional CD players with MiniDisc drives. S / PDIF cables are very thin, much thinner than DisplayPort and HDMI cables, which can be a huge advantage in some usage situations.

In order to use an S / PDIF connection, both the sender and the receiver device have to include this type of connection , otherwise it will be impossible and you will have to resort to other types of audio interfaces such as RCA. To this must be added that S / PDIF uses two types of connectors at the consumer level coaxial (RCA) and optical (Toslink). These two connections are not compatible with each other, not even with the use of adapters.

SPDIF port

The coaxial type S / PDIF connection is based on a mono RCA connector , normally this type of connector is orange so that the user can easily identify it, and do not confuse it with other RCA connectors that have other functions.

Coaxial SPDIF audio connection, jpeg

As for the optical type S / PDIF connection , it is based on a square connector called Toslink . These Toslink connectors have no other use, so it is impossible for the user to confuse them. Toslink connectors are based on fiber optic cable, a much more advanced technology than RCA-type copper cables.

There is a second type of optical type S / PDIF connector, this is based on a 3.5 mm jack connector , the same as the one used to connect headphones. This type of door has the advantage that it can be easily integrated into many devices, including laptops. There are adapters between the two types of optical S / PDIF connections.

SPDIF Toshlink to 3.5mm jack adapter

The following table summarizes the main technical characteristics of S / PDIF:


75 ohm coaxial or fiber optic


RCA or Toslink

signal level

0.5 to 1 V



Subcode information

SCMS copy protection information

Maximum resolution

20 bits (24 bits optional)

S / PDIF connection usage examples

The most common use for the S / PDIF interface is to set up home theater equipment . In this case you will have two main components, the transmitter that will be the cinema equipment itself, and the receiver that will be the television to which you are going to connect it. There will also be cases where you have an amplifier which sits between the two devices.

SPDIF on home theater equipment

Audio amplifiers typically don't include HDMI and DisplayPort ports. Therefore, the only way to use a digital audio signal in these cases is through the S / PDIF interface. If you're not using an amplifier and just want to connect your home theater equipment to the TV, you can choose to use an HDMI cable. This cable will transmit both the video and audio signals to you.

You may also have quite old audio equipment that doesn't include an HDMI port . In these cases you would also be forced to use the S / PDIF connection to transmit audio. To this you will have to add another type of connection to send the video signal to the television.