What is SPDIF & Optical? (S/PDIF vs Optical): Detailed Comparison

S/PDIF vs Optical: What is the difference between SPDIF and optical? S/PDIF and Optical ports are available on many home entertainment devices, including Blu-ray players, set-top boxes, game consoles, PCs, etc. You can use these ports to connect a source device to a receiver, amplifier, speaker system, or soundbar. Both standards are capable of carrying digital audio signals.

However, it seems like many get confused between S/PDIF and Optical often. Odds are you’ve seen these ports behind your TV or other media device, now wondering what they are and how they’re different. This “SPDIF vs Optical” comparison guide will answer your questions and clear your doubts regarding the audio interfaces.

What are S/PDIF and Optical?

Let this be clear: it’s possible to plug in both optical and coaxial cables in a S/PDIF jack, but the optical port only accepts optical (TOSLINK) cables. If you have an optical cable, you can use any of the interfaces to connect your TV to a speaker system.

Furthermore, both interfaces are digital, even though the coaxial cables for S/PDIF use the same type of connector found on analog RCA cables. However, don’t mix the digital coaxial and analog RCA cables as they’re different.

What is S/PDIF?

S/PDIF is an acronym for the Sony/Philips Digital Interface and the Sony/Philips Digital Interconnect Format. As the name suggests, Sony and Philips designed and developed this interface way back in the ‘90s.

Since S/PDIF is a data link layer protocol, it can transmit signals over either fiber optic cables with TOSLINK connectors or coaxial cables with RCA connectors. The particular format remains an interconnectivity medium for audio in today’s home entertainment systems and other Hi-Fi components.

Based on the AES3 standard, S/PDIF can carry two uncompressed PCM audio channels or compressed 5.1/7.1 surround sound. However, its inability to transmit lossless surround sound formats is notable due to the bandwidth limitations.

What is Optical?

Optical or TOSLINK (also known as Toshiba Link) is an audio interface that can convert digital audio signals to light beams and transmit them through a glass or plastic fiber optic medium. It utilizes the same software layer as S/PDIF, but it uses fiber optics over the electrical copper of coaxial cables.

With TOSLINK, the output electrical signals convert to red light beams that travel through the cable. The receiver on another end converts the optical signals to electric so that the input device can read them. Optical cables are also immune to external electromagnetic and radio frequency interference, unlike coaxial ones.

Optical can carry two channels of uncompressed PCM audio or compressed 5.1/7.1 surround sound formats, e.g., Dolby Digital, DTS Surround Sound. However, the bandwidth limitations make it incapable of carrying lossless Dolby TrueHD or DTS-HD Master Audio signals.

S/PDIF vs. Optical: Detailed Comparison

Followed so far what S/PDIF and Optical are? Now, we’ll walk you through the differences and similarities between them.

• Judging by how they work, optical can be S/PDIF while S/PDIF can’t necessarily be optical. You can consider TOSLINK as a subset of the S/PDIF connector rather than a different signal transmission system.
• Optical cables with TOSLINK connectors are generally shorter in length and more fragile than coaxial “S/PDIF” cables with RCA connectors. It’s because of the materials used in these cables.
• The optical interface makes use of fiber-optic cables. Compared to the primitive coaxial cable generally used with S/PDIF, it reliably transmits signals and consumes less power. Plus, the use of light beams for data transmission makes optical insusceptible to EMI or RFI and signal loss over longer distances.
• In contrast to the fragile glass or plastic fiber optics used in optical cables, coaxial S/PDIF copper cables are more durable. Granted, they aren’t as flexible or slim as TOSLINK cables, but they can survive bending, kinks, and pulls without permanent damage.
• Optical TOSLINK cables use an odd-shaped, squarish connector, whereas coaxial cables use the RCA phono connector. The optical cable’s connector goes in one way, and the connection doesn’t nearly feel as secure as the coaxial cable’s RCA jack.
• Both interfaces support a wide array of compressed audio formats regardless of the different connector types. However, they fall behind HDMI in terms of audio quality and bandwidth.
• Neither optical nor S/PDIF (coaxial) can carry lossless or uncompressed surround sound audio formats.
• Both S/PDIF and Optical are digital audio interfaces. The latter generally refers to the ADAT protocol over a fiber-optic TOSLINK cable, whereas S/PDIF makes use of a coaxial copper cable.
  Optical can carry up to 8 channels at 44.1/48 kHz or 4 channels at 88.2/96 kHz. S/PDIF can carry only two channels (stereo). Note that the optical interface can carry stereo S/PDIF signals too.
• When it comes to connecting modern TVs with speaker systems, game consoles, AV receivers, and other media devices, the use of optical is more relevant. S/PDIF, on the other hand, is seen on older media devices like DVD players and HTPCs, ones that only accept coaxial cables with RCA connectors.

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Pros and Cons of S/PDIF (Coaxial) and Optical

As you can see, the similarities and differences are less about S/PDIF and Optical and more about the cable and connector they use. Therefore, without going too much into detail, here are their main pros and cons:

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S/PDIF vs Optical: Wrapping up

With that, this “SPDIF vs Optical” comparison guide comes to an end. Assuming you now have a clear idea about S/PDIF and Optical, the decision about what to use depends on what’s available to you. If it’s an option, we’d also recommend going with HDMI for connecting AV devices.

Once again, S/PDIF refers to a data format, where the data transmission can take place over various types of cables and connectors. Optical or TOSLINK is a physical medium, through which the signals go from one end to the other. It doesn’t even necessarily mention the connector type.

For the sake of the comparison, we’ve often associated S/PDIF with coaxial cables here, as the “S/PDIF” connector on most media devices accepts only the coaxial RCA cables.

Similarly, the “Optical” connector supports only TOSLINK cables, but it doesn’t tell us whether it uses the S/PDIF or ADAT protocol. That’s something you should look for in your device’s user manual.