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Optical Digital Audio
- Cable And Connection Explained

Optical digital audio connections are a popular way to send high quality audio between devices. You might have a number of different choices when it comes to the audio for your system, and optical is always a good choice.

So what are they exactly, and what are the advantages and disadvantages?

What does the optical connector look like?

Optical audio connection on rear of amplifier

Optical digital audio uses a connection on your device like this one on the far left (clue - it's hiding underneath the word optical!)

In this example, there is an optical output on the left and a coaxial connection on the right - as well as other connections that we're not interested in right now.

When connecting two devices together, one device will have an optical output (the device sending the sound like your TV), and the other will have an optical input (the device receiving the sound like your amplifier).

If the optical port hasn't been used before, there should be 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.

When you remove the cap you will be able to see the bright red light from inside the device.

What does the optical  audio cable look like?

Optical Audio Cable

An optical audio cable looks like this.

When you insert the cable it should click into place. It is designed to fit one way only, one side is squared-off while the opposite is rounded on the corners. If you look carefully you will see that this matches the shape of the port on your device.

What does an optical digital audio cable do?

An optical digital audio connection is used to send digital audio signals between devices.

It supports stereo audio and Dolby Digital and DTS 5.1 multichannel audio for people with surround sound systems.

It does not support SACD, DVD-A or high-definition audio such as Dolby TrueHD and DTS-HD Master Audio. Check out our home theater glossary if you don't know what these are.

When should I use an optical connection?

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 a good way to transfer the audio between devices. You will be able to hear standard stereo audio and 5.1 surround sound transmissions over an optical connection.

Some devices with HDMI ports don't actually support the transfer of audio via HDMI. Therefore, this would be another instance where you could utilize this alternative digital interface.

Another common use for this type of connection is for connecting your HDTV sound to your speaker system. If you get your TV transmissions via an internal tuner, or a smart TV app, then you might want to get the audio into your home theater speaker system.

Most modern TVs have an optical audio output for this purpose. You connect the optical audio output on the rear of your TV to an optical input on your amplifier or receiver.

What else can you tell me about optical audio?

This type of interface is often referred to as a TOSLINK port - and the interconnect a Toslink cable. This makes reference to the developer of this connection type, Toshiba.

In this type of connection, the digital audio signal is converted into light and transferred via a cable made from optical fiber.

Aside from an HDMI connection, there are two main methods of connecting devices to send digital audio - optical and coaxial digital audio. Both of these methods of sending digital audio are also known as S/PDIF connections. Regardless of the connection type used, there is no difference in the actual data transferred.

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

Optical audio switchOptical Audio Switch - 3 In 1 Out

The main advantage of using fibre optic digital audio over coaxial is that optical digital audio cables are smaller and more flexible, and aren't affected by electrical and magnetic interference. However, a well-made coaxial cable with good shielding shouldn't have many issues in this respect either.

If you have a limited amount of optical inputs on your AV receiver, then you can buy an optical audio switch, like the one pictured above,  to channel two or more optical outputs into one. You can also get an optical splitter (1 in - 2 out) to send the same signal to two different devices at the same time.

Similarly, an optical to coaxial digital audio converter is available to convert one S/PDIF type into another.

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