You may have noticed a jack on your computer, TV, or amplifier labeled S/PDIF OUT. But do you know what it is for and how to use it? In this article, we'll explain what S/PDIF is, what its advantages and disadvantages are, and how to connect it to enjoy quality digital sound.
What is S/PDIF?
S/PDIF (for Sony/Philips Digital Interface) is a digital audio data transmission format . It was jointly developed by Sony and Philips in the 1980s to allow digital audio devices to be linked together without loss of quality. S/PDIF can transmit up to two channels of audio (stereo) with a maximum resolution of 24 bits and a sampling rate of 192 kHz.
S /PDIF comes in two forms: optical and coaxial. The optical form uses fiber optic cable with Toslink or mini-Toslink connectors. The coaxial form uses coaxial cable with RCA or BNC connectors. The two shapes are compatible with each other, provided you use an appropriate adapter.
How to connect S/PDIF?
To connect S/PDIF, you need a transmitter device with an S/PDIF output (optical or coaxial) and a receiver device with an S/PDIF input (optical or coaxial). You must then connect the two devices with a suitable cable (optical or coaxial), respecting the polarity of the connectors.
You must then select the S/PDIF source on the receiving device , using the remote control or the corresponding button.
You must also check that the audio format sent by the sending device is compatible with the receiving device. For example, if the transmitting device sends Dolby Digital, the receiving device must be able to decode it. Otherwise, you must change the audio format on the transmitting device, using the corresponding menu or button.
Some examples of S/PDIF connection
Here are some examples of S/PDIF connections depending on the devices you own:
- If you have a CD player and a digital amplifier , you can connect the CD player to the amplifier with an optical or coaxial S/PDIF cable. You will be able to enjoy quality digital stereo sound.
- If you have a DVD player and a home theater system, you can connect the DVD player to the home theater system with an optical or coaxial S/PDIF cable. You will be able to enjoy multi-channel surround sound (Dolby Digital or DTS) depending on the disc you are playing.
- If you have a computer and digital speakers , you can connect the computer to the speakers with an optical or coaxial S/PDIF cable. You will be able to listen to music or watch videos with quality digital sound.
What are the advantages of S/PDIF?
The main advantage of S/PDIF is that it allows a digital audio signal to be transmitted without going through an analog/digital conversion (or vice versa), which avoids the quality losses associated with this process. S/PDIF is therefore ideal for connecting digital audio sources (CD player, Blu-ray player, game console, etc.) to amplifiers or digital speakers.
S /PDIF also allows the transmission of compressed audio formats such as Dolby Digital or DTS , which provide multi-channel surround sound (up to 5.1 channels) with reduced bandwidth. S/PDIF is therefore suitable for connecting audio-video sources (DVD player, TV decoder, etc.) to home cinema systems.
What are the disadvantages of S/PDIF?
The main disadvantage of S/PDIF is that it cannot transmit uncompressed audio formats such as Linear PCM or DSD, which provide higher sound quality but require greater bandwidth. S/PDIF is therefore limited for connecting high-resolution audio sources ( SACD player, network player , etc.) to amplifiers or high-fidelity speakers.
S/PDIF also presents some technical constraints, such as the need to use good quality cables of limited length (less than 10 meters) to avoid interference or transmission errors. S/PDIF also requires synchronization between the transmitter and receiver of the audio signal, which can lead to compatibility or sound lag issues.
Comparison table of S/PDIF audio formats
| Audio format | Number of channels | Resolution | Sampling frequency | Compression |
|---|---|---|---|---|
| Linear PCM | 2 | 16 to 24 bits | 32 to 192 kHz | No |
| Dolby Digital | 2 to 5.1 | 16 bit | 32 to 48 kHz | Yes |
| DTS | 2 to 5.1 | 16 to 24 bits | 44.1 to 96 kHz | Yes |
S/PDIF FAQ
What is the difference between S/PDIF and HDMI?
HDMI (for High Definition Multimedia Interface ) is a format for transmitting digital audio and video data. It can transmit up to 8 audio channels (7.1 channels) with a maximum resolution of 32 bits and a sampling frequency of 192 kHz. It can also transmit uncompressed audio formats such as Linear PCM or DSD, as well as compressed audio formats such as Dolby Digital Plus or DTS-HD Master Audio.
HDMI therefore has advantages over S/PDIF, such as better sound quality, greater compatibility and simplified connection (a single cable for audio and video). However, HDMI requires newer, more expensive devices , and may have copyright protection (HDCP) issues.
What is the difference between optical S/PDIF and coaxial S/PDIF?
Optical S/PDIF and coaxial S/PDIF are two forms of the same digital audio data transmission format. They have the same technical characteristics (number of channels, resolution, sampling frequency, etc.) and are compatible with each other.
The difference is in the type of cable and connector used. Optical S/PDIF uses a fiber optic cable with Toslink or mini-Toslink connectors. Coaxial S/PDIF uses a coaxial cable with RCA or BNC connectors.
The choice between the two forms depends mainly on the availability of sockets on the devices to be connected. It may also depend on personal preferences or practical constraints.
For example, some prefer optical S/PDIF to avoid electromagnetic interference that can affect coaxial S/PDIF. Others prefer coaxial S/PDIF for its robustness and ease of connection.
What devices are compatible with S/PDIF?
S/PDIF is a fairly widespread and standardized digital audio data transmission format It is therefore compatible with many digital audio devices, such as:
- CD, DVD, Blu-ray, SACD players , etc.
- Game consoles (PlayStation, Xbox, etc.)
- TV decoders (box, satellite, cable, etc.)
- Computers (sound card, motherboard, etc.)
- Amplifiers (integrated, home cinema, etc.)
- Speakers (active, wireless, etc.)
To check the compatibility of a device with S/PDIF , simply look if it has an S/PDIF socket (optical or coaxial) for output or input. You must also check that the audio format sent or received by the device is compatible with S/PDIF.
How good is S/PDIF sound quality?
The sound quality of S/PDIF depends on several factors, such as:
- The audio format used (linear PCM, Dolby Digital, DTS, etc.)
- The resolution and sampling rate of the audio signal
- The quality of the cable and S/PDIF connectors
- The quality of the transmitter and receiver of the audio signal
- The quality of audio devices connected to S/PDIF
In general, S/PDIF offers satisfactory sound quality for most common uses. It allows digital sound to be transmitted without loss of quality linked to an analog/digital conversion . It also allows you to transmit compressed audio formats that provide multi-channel surround sound.
However, S/PDIF does not provide the best possible sound quality. It cannot transmit uncompressed audio formats which provide superior sound quality. It may also have synchronization or interference issues that may affect the sound. If you want to connect your PC to your TV without HDMI , S/PDIF can be an alternative solution, provided that your devices have the corresponding sockets.
What is the future of S/PDIF?
S/PDIF is a digital audio data transmission format that has been around for over 30 years . It has been widely adopted by manufacturers and users of digital audio devices. It therefore remains a relevant and useful format for linking digital audio sources and systems.
However, S/PDIF faces competition from other newer and more efficient formats, such as HDMI or USB . These formats offer better sound quality, greater compatibility and greater ease of use. They are therefore increasingly present on digital audio devices.
S/PDIF is therefore not about to disappear, but it could lose its interest and popularity over time. It could remain a secondary or alternative format for connecting digital audio devices together .
Conclusion
You now know what S/PDIF OUT is and how to use it to enjoy quality digital sound . To summarize, the S/PDIF OUT is a socket that allows you to connect digital audio devices together without loss of quality . There are two types of S/PDIF OUT: optical and coaxial. You must choose the type that corresponds to the sockets available on your devices. You must also check that the audio format you want to listen to is compatible with S/PDIF OUT.
