Coaxial Digital Audio - Cable and Connection Explained

Coaxial Digital Audio - Cable and Connection Explained
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Updated: September 03, 2019

The coaxial digital audio cable is one of the most common methods used to transfer digital audio between devices.

However, it's not your only choice.

Here I take an in depth look at coaxial audio and look at when you might want to use it. In some cases it might well be the best solution for your system. Sometimes not.

I also discuss various ways of converting coaxial audio to different types of audio which may suit your system better.

What Does the Coaxial Connector Look Like?

Coaxial digital connection on the rear of a DVD player

A coaxial digital connection on your device looks like this. You can see it here in the example above.

It is a single female RCA connector which is often color-coded orange or black. You might find some that are not, so it's always best to double-check the labeling of the connection.

The port will often be labeled as 'coaxial', but may just say something like 'digital out' or 'digital in'.

It just requires one cable to transfer the signal, unlike analog stereo audio for example.

Your device may just have one input - or output - depending on whether it is designed to send or receive audio.

The device pictured above is a DVD player, so the coaxial connection is a digital output. Designed for sending the DVD audio to an amplifier or AV receiver.

As with all RCA connections, it doesn't matter which way round you insert the plug, it will plug-in regardless of the orientation. It should be a tight fit though, so you may have to push firmly.

What Does the Coaxial Digital Audio Cable Look Like?

Coaxial digital audio cable

Coaxial digital audio cables for transferring audio look like this.

They have one male RCA jack at either end, and the technical specifications say they should be rated at 75 ohms for accurate transfer of the signal.

Yet, in the real world, many AV cables may or may not be accurately designed to be 75 ohms. Whatever it may say on the packaging.

I wouldn't recommend spending large sums of money on expensive 'high-end' coaxial cables. 

There are some people that will swear blind that a more expensive cable designed for the specific purpose will sound better. I don't agree.

A well-made coaxial cable doesn't need to be particularly expensive.

However, you can make your own choice.

Amazon has some good quality and great value coaxial digital audio cables here.

How Is a Coaxial Cable Wired?

Internally, a coaxial cable has four main components:

  1. A center core which is usually made from copper wire.
  2. A dielectric (electrically insulating) plastic insulator. 
  3. A braided metallic mesh (which acts as a shield for electromagnetic interference).
  4. An outer plastic coating to protect the inside of the cable.
Coaxial Cable Wiring Diagram

What Does a Digital Coaxial Connection Do?

A coaxial digital audio connection is used to send S/PDIF digital audio signals between devices.

It supports stereo audio as well as DTS and Dolby Digital 5.1/7.1 surround sound signals.

It does not support DVD-A, SACD or high-definition audio such as DTS-HD Master Audio and Dolby TrueHD.

So, if you want to play back this type of audio, you will need to use an HDMI connection.

When Should I Use a Coaxial Digital Audio Connection?

The preferred method for transferring digital audio signals would usually be via an HDMI connector.

The reason for this is that HDMI supports every type of audio signal available and everything can be sent through one cable - video and audio.

However, if you don't have HDMI as an option, then a coaxial digital audio cable is an excellent way to send the audio between devices.

This type of connection will allow you to hear standard stereo audio and 5.1 surround sound.

A coaxial digital output is often used when sending multi-channel audio from a DVD player or computer to your surround sound system.

Or, from a CD player to a stereo amplifier. 

Your TV might have a coaxial out on the back. To send the audio to an amplifier or AV receiver. Although, newer TVs often seem to have an optical output for this purpose.

But, your TV might have coax instead.

It doesn't matter which. As long as you have the same type of input on your amplifier. And, even if you don't, you may be able to use a converter to switch from one to the other (see below).

Do I Have to Use a Coaxial Cable?

It is recommended to use a 75-ohm coaxial cable to transmit digital transmissions. This will help to avoid errors in the signal.

However, there's nothing to stop you using any RCA cable that you happen to have lying about. Like a composite video cable.

It should give you a working signal.

However, I wouldn't use one of these unless I had no other choice. I think a proper coaxial cable is best in this situation.

What Else Can You Tell Me About Coaxial Audio Connections?

This type of digital audio connection sends what is known as an S/PDIF signal.

There are actually two connection types which send this type of signal. One is this coaxial digital audio connection, and the other is an optical digital audio interface.

It is common to find both of these connections side-by-side on a device - or you may get one or the other.

If you have both it doesn't really matter much which one you use, it may just come down to the type of connection you have on the other device.

One advantage of using digital coaxial cables over optical audio is that these cables are quite common. You are more likely to have an RCA cable to hand than an optical one.

It is also likely to be more robust than the thin optical cable. Apart from that, the differences between the two methods are quite small.

Can I Convert Digital Coaxial to Optical Audio?

You're in luck. You can indeed.

If you need to connect a coaxial output to an optical input, you can buy a coaxial to optical converter to convert one S/PDIF type into another.

The one pictured below takes a coaxial digital audio output (e.g. from your Blu-ray player) and converts it to an optical signal that you can input into your amplifier.

Coaxial to Optical S/PDIF Audio Converter Coaxial to Optical S/PDIF Audio Converter

Other converters will do this conversion the other way around, so check carefully before you buy to make sure you get the right one that you need.

If you're still unsure, you could play it safe and get a converter that can handle both optical and coaxial S/PDIF audio.

Bi-directional Optical/Coaxial Audio Converter & Splitter Bi-directional Optical/Coaxial Audio Converter & Splitter

This 2-way optical/coaxial audio converter can accept either a coaxial or optical signal as the input, and then outputs both formats.

Therefore, you can not only use it as an S/PDIF audio converter, it can also be used as a splitter to send the audio signal to two different places at the same time.

In some circumstances, that can be really useful.

Can I Convert Coaxial Digital Audio to RCA Analog Stereo?

So, here’s the thing. You have a digital coaxial output on your playback device. Let’s say your Blu-ray player.

However, you only have stereo RCA inputs on your amplifier. How are you going to hear the audio from your movie over your stereo speakers?

The solution is to buy a coaxial digital audio to analog RCA converter, like the one pictured below.

Digital Optical Coax to Analog RCA Audio Converter Digital Optical Coax to Analog RCA Audio Converter

This model will accept either a coaxial or optical digital audio signal, and output it as stereo analog audio. It supports four sample rates from your playback device – 32, 44.1, 48 and 96 kHz.

This device can be used in any situation where you need to convert S/PDIF digital audio to analog stereo audio.

Bear in mind, if you are sending the movie audio to a stereo speaker system, then you will want to select the stereo soundtrack on the playback device.

Either that or many players can be set to downmix a surround sound mix to stereo.

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About Home Cinema Guide

Paul started the Home Cinema Guide to help less-experienced users get the most out of today's audio-visual technology. He has worked as a sound, lighting and audio-visual engineer for around 20 years. At home, he has spent more time than is probably healthy installing, configuring, testing, de-rigging, fixing, tweaking, re-installing again (and sometimes using) various pieces of hi-fi and home cinema equipment.

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