Optical Digital Audio Cable & Connection Explained

Optical digital audio connections are a popular way to send high-quality audio between devices. They are also known as TOSLINK connections.

However, you might have several different options for the audio for your sound system, so what is optical audio exactly?

Is optical always the best choice – and what are the advantages and disadvantages over HDMI?

Also, is optical audio better than a coaxial connection? And, can you buy optical audio adapters to convert optical to coaxial – or into stereo analog audio?

Read on to find the answers to these questions and more.

Best Optical Audio Cables Comparison Table

What Does the Optical Connector Look Like?

An optical digital audio connection on your device will look something like this:

Clue – it’s on the right, hiding above the word optical!

In this example, there is an optical output and a coaxial connection above it – plus some other connections that don’t matter right now.

When connecting two devices, one device will have an optical output. This is the device sending the sound – like your TV, for example.

The other will have an optical input. This is the device receiving the sound – like your amplifier.

In the picture above, the optical port has a protective ‘door’ that will move out of the way when you push the cable in.

Some optical ports have a protective cap over the hole, which needs to be removed before you can plug in the cable. As is the case in the picture here with this optical digital audio out:

When you remove the cap, you will see the bright red light inside the device.

What Does the Optical Audio Cable Look Like?

An optical audio cable looks like this:

When you insert the optical cable, it should click into place. It is designed to fit one way only; one side is squared-off while the opposite is angled on the corners.

If you look carefully, you will see that this matches the shape of the port on your device.

This can often confuse people when connecting an optical cable to their TV or amplifier.

You will find that some cables have a thicker wire between the connectors. This won’t affect the sound, so don’t worry too much about this.

What Does an Optical Digital Audio Connection Do?

An optical digital audio connection sends stereo or 5.1 S/PDIF digital audio between devices.

An everyday use for this type of connection is the digital audio output on the back of your TV.

By connecting this output to an amplifier, you can quickly improve the sound of your television.

Other devices that typically have an optical out are Blu-ray and DVD players and game consoles.

Devices that commonly have an optical audio input are amplifiers, AV receivers, hi-fi DACS (digital to analog converters), and soundbars.

What Audio Formats Are Supported by an Optical Connection?

Optical audio connections support the following audio formats:

• Lossless 2.0 (stereo) PCM audio
• Compressed Dolby Digital 2.0/5.1 and Dolby Digital EX
• Compressed DTS Digital Surround, DTS-ES Matrix 6.1 and DTS-ES Discrete 6.1

Due to bandwidth restrictions, optical outputs do not support multichannel LPCM, Dolby Digital Plus, Dolby Atmos and DTS:X – or high-definition audio such as Dolby TrueHD and DTS-HD Master Audio.

Discrete 7.1 soundtracks are not supported as they are only encoded in higher resolution audio formats.

Due to copyright restrictions, optical connections also do not support SACD audio and DVD-Audio.

If you try to play unsupported formats on your player via an optical output, the player will usually downmix to stereo – or play a lower resolution version of the audio.

The manual for your player will tell you how it will handle any unsupported audio formats.

Check out the home theater glossary if you don’t know what these types of audio are.

When Should You Use an Optical Connection?

A common question is, do you need to use optical audio with HDMI?

If your AV equipment has an HDMI port, then in most cases, it would be best to transfer the audio signals via HDMI.

This is because HDMI supports all types of audio signals, and you can send all the video and audio signals via one cable.

However, if you don’t have HDMI as an option, then an optical audio cable is an excellent way to transfer the audio between devices.

You will be able to play uncompressed stereo audio and compressed DTS or Dolby Digital 5.1 surround sound over an optical connection.

Some older devices with HDMI ports don’t support audio transfer via HDMI. Therefore, this would be another instance of utilizing this alternative digital interface.

Another everyday use for this type of connection is connecting your TV to your hi-fi sound system or soundbar – or wiring your CD player to an amplifier.

For example, if you get your TV transmissions via an internal tuner or a smart TV app, you might want to send the audio from your TV into your home theater speaker system.

Most modern TVs have an optical audio output for this purpose.

Simply connect the optical audio output on the rear of your TV to an optical input on your AV receiver or amplifier.

What Else Can You Tell Me About Optical Audio?

This type of interface is often referred to as a TOSLINK port, and the wire a TOSLINK cable. This refers to the developer of this connection type, Toshiba.

The digital signal is converted into light in an optical connection and transferred via a cable made from optical fiber.

This fiber optic cable can be pretty thin, so you need to be careful when handling it. You can break the core if you bend it too much.

Optical cables for digital audio are usually constructed with multimode plastic optical fiber (POF).

This is cheaper than alternative options such as glass or silica optical fibers – but is ideally suited to short runs typical in home audio applications.

Plastic optical fiber is also more flexible, another benefit when wiring a sound system.

Aside from an HDMI cable, there are two primary ways of connecting devices to send digital audio – optical and coaxial digital audio.

Both of these connection types are also known as S/PDIF connections.

S/PDIF is short for Sony/Philips Digital Interface. Sony and Philips were both involved in the initial design of this audio connection.

Regardless of the connection type used, there is no difference in the transferred data.

You often find these two connections side-by-side on a device – as in the picture at the top of the page – or you may get one or the other.

If you have both, deciding which one to use will usually come down to something simple such as the type of connection you have on the other device.

How to Connect an Optical Cable From Your TV to Home Theater

Connecting an optical cable from a TV to a home theater system is relatively simple. The basic steps are:

1. Remove any protective caps from the optical cable, TV optical output and home theater system optical input.
2. Connect the cable from the TV’s optical out to the home theater’s optical input – making sure to line up the connector correctly as it will only insert one way round.
3. Switch on the TV and amplifier and ensure that the TV’s output is enabled and the correct input is selected on the home theater system.

For more detailed information on this, go to how to connect an optical audio cable to your TV and soundbar.

Does Your TV Pass 5.1 Surround Sound Through the Optical Output?

A common issue for some people is they can’t get 5.1 surround sound from their TV’s optical output to their sound system or soundbar.

This can be a problem because the optical audio outputs of some TVs don’t passthrough a surround sound signal from external devices.

For example, you might have a TV, a DVD player and a soundbar.

The DVD player connects to the TV via HDMI, and the TV’s audio is sent from the optical output to the soundbar.

So far, so good.

But when you hear the DVD’s movie audio on your soundbar system, you only get stereo audio – not 5.1 surround.

The likely reason is that your TV doesn’t support passing through the 5.1 audio from the DVD player to its optical output – and it will only downmix the sound to stereo.

Some TVs will passthrough Dolby Digital 5.1 audio and not DTS – or vice versa. While others may downmix all external audio to stereo.

So, if you think this might be a problem in your setup, you should check if the new TV you buy supports 5.1 audio passthrough via optical.

If you already have this problem with your existing equipment, there are a couple of solutions that may work, depending on the hardware that you have:

1. Connect your DVD player directly to the soundbar rather than the TV. This will require your soundbar to support multiple inputs.
2. Connect your TV and soundbar using HDMI ARC/eARC, rather than optical
3. Use an HDMI audio extractor to split the 5.1 audio from the DVD player’s HDMI output, and send the optical signal directly into the soundbar. You may also need an optical audio switch if your soundbar only has one optical input.
4. Use an AV receiver and speakers for your surround sound, rather than a soundbar. You can then connect the DVD player directly to the receiver.

This article summarizes the 5.1 passthrough support for many new TV models.

This issue is only likely to affect audio from external devices, and the audio from streaming apps on the TV itself should pass surround sound OK.

However, if you have an issue with surround sound from an app like Netflix or Disney+, always check your TV’s support for streaming audio via the optical output.

And that the show you are playing does have a 5.1 soundtrack!

What is the Best Optical Cable?

Optical cables used for digital audio come in a wide range of lengths, colors – and prices!

You may be tempted to buy the most expensive optical cable on the market because… well, it’s going to sound better, right?

Not really, no.

You won’t get extra special audio by spending an excessive amount on a cable. Just buy a good value, well-made brand – and note the emphasis on well-made.

The cheaper cables are pretty thin, so you should be careful when connecting your equipment together.

More expensive cables will usually be thicker and have more shielding – more like a standard RCA digital audio cord – but the thickness of the wire won’t influence the performance.

However, the more expensive cables may prove more robust and should cope better if you regularly reconfigure your wiring. They will also likely perform better if you run the cable over a long distance.

You may see cable manufacturers claim that their optical cables support the transfer of high-resolution audio and Dolby Digital Plus.

While this might be technically true in terms of bandwidth, you are unlikely to find many devices that will support these audio formats via their optical connections.

So, where can we go and buy an optical audio cable?

Many choices are available on Amazon, so just check the reviews and buy one there – or you can support your local AV store.

The AmazonBasics digital optical audio cable should do the job just fine – however, there are other good value brands there too, like this KabelDirekt digital optical audio cable:

Just make sure you double-check the length of the cable you are buying and get the right size for your needs.

There’s nothing more annoying than buying a cable and then finding out it’s too short.

Been there. Done that.

What Is the Maximum Length of an Optical Audio Cable?

A well-made optical audio cable should work well up to 5 meters. You may even find that you will get a good signal at 10 meters or more.

However, by the time you get to this length, you are more likely to run into problems.

It would certainly be worth considering buying a higher-quality digital optical cable for longer runs.

However, bear in mind that your equipment will also impact this.

The electronics built into your hardware can vary in quality, and you may find that some devices will work over a long cable run – while others don’t.

You may just have to try it and see.

Alternatively, you could consider buying a set of optical audio extenders like this:

These extenders use Cat5 or Cat6 cable to send the optical audio signal over very long distances.

They work up to a distance of 300 meters and also support coaxial audio connections.

Which Is Better – Optical vs HDMI?

Many people wonder which connection they should use to send audio between their devices – optical or HDMI cables.

Firstly, do they sound different? No, they don’t.

If you are sending the same audio format, it will sound the same regardless of whether you are using optical or HDMI.

The main advantage of HDMI over an optical connection is that HDMI supports more audio formats.

Optical and HDMI both support uncompressed stereo – and 5.1 Dolby Digital and DTS audio.

However, HDMI also supports Dolby Digital Plus and high-resolution audio like Dolby TrueHD, DTS-HD Master Audio, Dolby Atmos and DTS:X.

Also, HDMI has the advantage of HDMI ARC and HDMI eARCconnections, where you can send audio from a TV to a soundbar or AV receiver.

This can sometimes save you from installing an extra cable in your system.

Here is a handy table comparing the differences between optical and HDMI ARC and HDMI eARC connections:

The bottom line? HDMI supports more audio formats and might save you an extra cable if your system supports ARC or eARC.

However, an optical connection will sound just as good as HDMI if you don’t need anything more than stereo or compressed 5.1 surround sound.

Which Is Better – Optical or Coaxial Audio Connections?

Optical and coaxial offer comparable audio quality for the same audio format – and both send S/PDIF digital audio signals.

TOSLINK connections were originally designed to run to a maximum of 48 kHz. However, many newer devices increased the supported resolution to 24/96.

This is commonly thought to be the maximum resolution of optical audio – although there is a question of why many devices don’t support higher resolutions.

Coaxial connections commonly support 24/192 resolution audio, so higher resolution audio formats may be one reason to choose coaxial over optical audio.

A potential benefit of optical connections is that they won’t be affected by electromagnetic interference. In theory, coaxial could be.

Another consideration is that the sound quality may vary by device.

Before you hear a digital audio signal, it needs to be converted to analog audio.

A DAC performs this process, so a poorly designed device may create audible differences when using the optical or coaxial inputs, whereas a high-quality device shouldn’t sound any different.

There won’t be much difference between the sound quality of optical and coaxial connections in the real world – and the one you choose will usually depend on your devices’ connections or the cables you have available.

How Do You Convert Digital Optical Audio to RCA Coaxial?

There are times when you can use an audio converter to solve problems passing audio between devices.

For example, you might have an optical output on your Blu-ray player but wish to send audio directly into your amplifier – which only has a coaxial digital audio input.

However, there is a simple solution. You can buy an optical audio converter to change the audio to an RCA coaxial output, like the one pictured below:

This will take an optical output and output the audio signal via coaxial.

Terrific!

The one highlighted above is bi-directional, which means that you can also use it to convert a coaxial output to an optical input. This can prove to be really useful in some situations.

Converters can solve many potential problems when mixing and matching different audio types and connections.

You just need to make sure that the converter will pass all the signals you want.

For example, some may only send stereo audio and not multichannel surround sound. The one above supports both.

Can You Convert Optical Audio to Stereo Analog RCA?

Another solution to the problem of the wrong inputs on your amplifier would be to convert the optical digital audio to analog and connect to your amplifier using an old friend, the stereo analog audio connection.

But how can you possibly do this? Well, buy a digital optical to analog RCA audio adapter, of course.

You can see an example of one pictured below:

This device will accept either an optical or coaxial digital audio connection and output the audio as stereo analog.

For more detail on these converters, take a look at how to convert optical audio to RCA stereo.

How to Convert Analog RCA to Digital Optical Audio

In the previous example, you learned how to convert digital to analog audio.

However, what if you needed to convert the audio the other way? From analog to digital.

An example might be where you have a device like an old tape deck – and wanted to send the audio to the optical input of an amplifier or soundbar.

You can do that with a converter like this:

The above device also converts to a coaxial output as well as optical.

Before buying any converters like these, always make sure you know the audio output and input format.

If you get a device that converts the wrong way, it won’t work.

What Is an Optical Audio Switch Used For?

Another potential issue you may come across is that you have a limited number of optical inputs on your AV receiver or soundbar.

In this scenario, if you have two or three devices that you want to connect into your amplifier via an optical connection, then you can buy an optical audio switch, like the one pictured below:

This little box of tricks will accept the optical audio outputs of up to three devices and output them into a single input on your amplifier.

The model above comes with a remote control to switch between the different audio inputs.

Frequently Asked Questions