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?
A coaxial digital connection on your device looks like this:
It is a single female RCA connector that 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 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 digital 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.
Some people will swear blind that a more expensive cable designed for a specific purpose will sound better. I don’t agree.
A well-made coaxial cable doesn’t need to be particularly expensive. Something like this will be fine:
However, you can make your own choice.
Amazon even has their own AmazonBasics range of digital audio coaxial cables which will do the job for most tasks.
You can also use this type of cable to connect your AV receiver to a subwoofer.
How Is a Coaxial Cable Wired?
Internally, a coaxial cable has four main components:
- A center core which is usually made from copper wire.
- A dielectric (electrically insulating) plastic insulator.
- A braided metallic mesh (which acts as a shield for electromagnetic interference).
- An outer plastic coating to protect the inside of the cable.
This makes it a robust cable type that is used for many different applications.
What Does a Digital Coaxial Connection Do?
A coaxial digital audio connection sends S/PDIF digital audio signals between devices.
S/PDIF stands for Sony/Philips Digital Interface – who were the initial designers of this type of digital audio transmission.
Two connection types send this type of signal. One is the coaxial digital audio connection being discussed here, 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 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 a coaxial 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.
What Audio Formats are Supported by a Coaxial Digital Audio Connection?
A coaxial digital audio connection supports uncompressed PCM stereo audio and DTS and Dolby Digital 2.0/5.1 surround sound signals.
Dolby Digital EX, DTS-ES Matrix and Discrete 6.1 soundtracks will also play without a problem.
Coaxial does not support multichannel LPCM, Dolby Digital Plus, Dolby Atmos, DTS:X or high-definition audio such as DTS-HD Master Audio and Dolby TrueHD.
Due to licensing restrictions, you also cannot play DVD-Audio or SACD audio.
7.1 soundtracks are only available in high-resolution formats, and so they won’t play as intended either.
Your player’s manual will tell you how it will handle any unsupported audio formats sent via the coaxial output.
The most common solutions are to downmix the audio to stereo PCM – or the player may simply output a lower resolution version.
If you want to play this type of audio as intended, 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 from 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.
How Can I Extend a Coaxial Digital Audio Cable?
What can you do if your digital coaxial audio cable is too short?
Well, firstly, you could buy a cable that is the right length in the first place!
But, I appreciate my wise guy answer isn’t going to help you much in your hour of need.
Of course, you may be relocating your equipment and the cable that you were using is now too short.
So, can you extend a digital audio coaxial cable?
Yes, it’s quite easy.
All you need is to buy a female to female RCA adapter. Also known as a coupler:
Of course, you will also need another coaxial cable! If you already have a second coaxial cable, then it’s even better.
Then, just connect the two cables with a single coupler and you will be good to go.
Will this degrade the audio performance?
It shouldn’t do. The manufacturer says the ones pictured above are suitable for a digital audio RCA cable. I have used similar connectors in the past without problems.
If you are going to buy a different brand, then it might be worth checking that they are suitable for a digital audio RCA cable before you buy.
I guess in an ideal world, I would rather use a single cable that is the right length.
But adapters like these can be a cheap and easy solution if you need to have a longer cable run.
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.
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.
This 2-way optical/coaxial audio converter can accept either a coaxial or optical signal as the input, and then outputs both formats.
Therefore, it can not only be used as an S/PDIF audio converter, but 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.
How Do I Connect a Digital Audio Out To an Amplifier RCA Input?
Many amplifiers and AV receivers have coaxial RCA digital audio inputs.
These receive the digital audio output from your device that is generating the sound. Like a TV or DVD player, for example.
So, how do you connect the digital audio out to an RCA input on an amplifier?
Well, that depends on the type of digital audio output on your TV, DVD, or Blu-ray player.
As I explained previously, there are two main types of digital audio output – coaxial and optical.
Connecting a Digital Audio RCA Output to an RCA Input
If your output device has a coaxial RCA audio connection, then it is easy to connect this to the RCA input on your amplifier.
You just need to buy a 75-ohm RCA coaxial digital audio cable like the one below:
Then connect this from the RCA output on your TV/DVD player to the RCA input on your amplifier. Job done.
Just make sure that you buy the right length cable for your system.
Give yourself a bit of slack for re-routing the cable in the future – or if you move your equipment. But try and get roughly the right length for the job in hand.
Avoid buying a 10m cable for a 2m distance. Go to this article for some more home theater wiring tips.
Connecting an Optical Digital Audio Output to an RCA Input
If your digital audio output is optical, then it’s a little more tricky – but not much.
Ideally, you would connect the optical output to an optical audio input on your amplifier.
However, if your amplifier only has a coaxial RCA input, then you will need to convert the connection from optical to coaxial.
You can do this with an optical to coaxial RCA converter like the one below:
In this case, connect an optical cable from your output device into the converter’s optical input.
Then, connect the converter’s RCA output to the amplifier RCA input with a coaxial digital audio cable.
So, it’s a bit more difficult, but easy enough when you have the correct converter.
Can I Split Coaxial Digital Audio and Send It to Two Different Devices?
What if you wanted to send a single coaxial digital audio output to two different playback devices?
For example, you might want to send the audio output of a TV to a soundbar and a separate DAC. Or, from a CD player to an amplifier and a DAC.
The solution is quite simple. You can buy an RCA Y-adapter audio cable similar to the one below:
All you need to do is connect the single male RCA to your coaxial audio output. You then have two female RCA connections to send audio into the inputs of your two devices.
The two inputs on your devices may well be female connectors too.
So you will need an extra male to male RCA digital audio coaxial cable to complete each of the connections.
A Y-cable, like the one above, can also be used for connecting two subwoofers to an AV receiver with a single subwoofer output.
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.
This model will accept either a coaxial or optical digital audio signal, and output it as stereo analog audio. It supports five sample rates from your playback device – 32, 44.1, 48, 96, and 192 kHz.
This device can be used in any situation where you need to convert S/PDIF digital audio to analog stereo audio.
It even has a headphone out too.
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.
If you are sending the audio from the digital coaxial audio output on a TV, then you will need to set the audio output format to PCM. This ensures that the TV sends stereo audio to the converter.
How Do I Convert From RCA Analog Stereo to Coaxial Digital?
There might come a time when you want to send analog audio into a digital audio input.
An example of this might be where you have an old tape deck with stereo analog outs – but you want to hear this through your speaker system or soundbar that only has a coaxial digital audio input.
In this case, you will need to buy an analog RCA to digital coaxial audio converter.
With the converter pictured above, you would connect the stereo analog audio output from your tape deck into the RCA inputs.
Then, connect a digital audio coaxial cable from the output into your amplifier or soundbar.
This device also has the advantage of supporting an optical audio output too.
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.