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Coaxial Digital Audio: What You Need to Know

two coaxial digital audio connections on the back of an AV receiver

Digital audio has become an integral part of our daily lives, from music streaming services to home theaters and gaming systems.

The coaxial digital audio cable is one of the most common methods for sending digital audio between devices.

Coaxial cables have a unique construction that allows them to carry digital audio information in electrical signals and are commonly used to connect audio components such as CD players, digital audio interfaces, and surround sound systems.

However, it’s not your only choice.

Sometimes, it might be the best solution for your devices – but often, it’s not.

This article will explore the basics of coaxial digital audio and how it works, including its advantages.

Whether you are a seasoned audio enthusiast or a newcomer to the world of digital audio, this article will provide a comprehensive understanding of coaxial digital audio and how it can enhance your audio experience.

Coaxial Digital Audio Cables Comparison

FosPower Digital Audio Coaxial Cable
  • Size: 3/6/10 feet
  • 24K gold-plated connectors
  • Color-coded connectors
Amazon Basics Digital Audio Coaxial Cable
  • Size: 4 feet
  • Gold-plated, split-tip RCA connectors
  • Easy-grip and color-coded for easy use
KabelDirekt Digital Audio Coaxial Cable
  • Size: 3/6/10/15/20/25 feet
  • 75 ohm impedance
  • Reliable build-quality

What Does the Coaxial Connector Look Like?

A coaxial digital connection on your device looks like this:

Coaxial digital connection on the rear of a DVD player

It is a single female RCA connector that is often color-coded orange or black – although 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.’

Unlike analog stereo audio, coaxial digital audio only requires one cable to transfer the signal.

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 that sends the DVD audio to an amplifier or AV receiver.

As with all RCA connections, it doesn’t matter which way round you insert the connector, and 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 digital signal transfer.

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

You don’t need to spend large sums on expensive ‘high-end’ coaxial cables – although some people swear blind that a more expensive cable will sound better.

A well-made coaxial cable doesn’t need to be particularly expensive, and something like this will be fine:

Good Value Coaxial Audio Cable
FosPower Coaxial Digital Audio Cable
What Is It: A cable for transmitting optical digital audio between devices.
  • Well-made cable with good shielding
  • Available lengths: 3, 6 and 10 feet
  • 75-ohm impedance for reliable signal transfer
  • Color-coded
  • Limited cable lengths

However, you can make your own choice.

The cable’s construction will be more critical over longer runs, so you may want to increase your budget a little if you need to buy a long cable – say, 20 feet or more.

Amazon even has its 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:

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

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 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 which one you use, and 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 pretty common, so 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 pretty small.

What Audio Formats Does a Coaxial Digital Audio Connection Support?

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.

However, a coaxial digital connection 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.

Audio format support for s/pdif coaxial and optical audio connections
Optical and coaxial connections audio format support

7.1 soundtracks are only available in high-resolution formats, 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 any unsupported audio as intended, you need to use an HDMI connection.

When Should You Use a Coaxial Digital Audio Connection?

The preferred method for transferring digital audio signals is via an HDMI connector.

This is because 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 to send multichannel audio from a DVD player or computer to your surround sound system – or a CD player to a stereo amplifier.

Your TV may even have a coaxial out on the back, which you can use to send TV audio to an amplifier or AV receiver – although modern TVs often have an optical output for this purpose.

If you have both, it doesn’t matter which you use as long as you have the same input type 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 You Have to Use a Coaxial Cable?

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

However, there’s nothing to stop you from using any RCA cable that you happen to have lying around – like a composite video cable.

It should give you a working signal.

However, it’s best not to use one of these unless you have no choice, so a proper 75-ohm coaxial cable is best in this situation.

How to Extend a Coaxial Digital Audio Cable

What can you do if your digital coaxial audio cable is too short?

For example, you may be relocating your equipment, and the cable you used is now too short.

Can you extend a digital audio coaxial cable?

Yes, it’s pretty easy.

All you need is to buy a female-to-female RCA adapter, which is also known as a coupler:

Of course, you will also need another coaxial cable to connect to the other side of the coupler – so if you already have a second coaxial cable, that’s great.

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. They will probably be fine for a digital audio RCA cable, so you shouldn’t get any glitching.

However, sometimes you just have to try it and see how you get on.

But, the longer the cable you create, you will increase the chances of the signal dropping out.

You can also use this coupler to extend a subwoofer cable, along with component video and composite video RCA cables.

In an ideal world, it would be best to use a single cable that is the correct length – but adapters like these can be a cheap and easy solution if you need to extend a cable run.

Can You 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, which converts one S/PDIF type into another.

The one pictured below takes a coaxial digital audio output – like from your Blu-ray player – and converts it to an optical signal that you can connect to your amplifier.

Top Coaxial to Optical Audio Converter
ROOFULL Optical to Coaxial Bi-Directional Digital Audio Converter
What Is It: A converter for changing Toslink optical audio to coaxial - or from coaxial audio to optical.
  • Use it if you don't have the correct digital audio connections on your device
  • Bi-directional so you can convert both ways
  • Supports uncompressed stereo PCM audio and 5.1 Dolby Digital and DTS
  • Works up to 30 meters
  • Power connection required

Be careful when buying one of these.

Some converters will only work one way – from coaxial to optical, for example – so it’s important to buy the correct one for the job.

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

The one suggested above is bi-directional, meaning you can convert digital audio signals either way – from coaxial to optical or from optical to coaxial.

However, a converter that only works in one direction, might be slightly cheaper.

The model suggested above also sends the signal from both outputs at the same time.

Therefore, it can be used as an S/PDIF audio converter and as a splitter to simultaneously send the audio signal to two different places.

In some circumstances, that can be really useful.

How Do You 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 the source device, like a TV or DVD player.

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 explained previously, there are two main types of digital audio output – coaxial and optical – so here is how you would connect them both.

Connecting a Digital Audio RCA Output to an RCA Input

Connecting to your amplifier’s RCA input is easy if your output device has a coaxial RCA audio connection.

You just need to buy a 75-ohm RCA coaxial digital audio cable like the one below:

Good Value RCA Coaxial Cable
Mediabridge Ultra Series Digital Audio Coaxial Cable
What Is It: A good quality coaxial RCA cable for digital audio signals or subwoofer cables.
  • Well made and from a popular brand
  • Dual shielding to reduce interference
  • Available lengths: 2, 4, 8, 15 and 25 feet
  • Gold-plated connectors

Then connect this from the RCA output on your TV or DVD player to the RCA input on your amplifier. Job done.

Connecting a Coaxial Digital Audio Output to an RCA Input
Connecting a coaxial digital audio output to an RCA input

Just make sure that you buy the correct length of 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.

So, try to avoid buying a 10m cable for a 2m distance, for example.

Follow the link for some more home theater wiring tips.

Connecting an Optical Digital Audio Output to an RCA Input

If your digital audio output is optical, 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, 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 to the converter’s optical input.

Then, connect the converter’s RCA output to the amplifier’s RCA input with a coaxial digital audio cable.

Connecting an Optical Digital Audio Output to a Coaxial RCA Input
Connecting an optical digital audio output to a coaxial RCA input

So, it’s a bit more complicated but easy enough when you have the correct converter.

How to Split Coaxial Digital Audio and Send It to 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 a TV’s audio output 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:

Top Short RCA Y-Adapter Cable
Mediabridge Ultra Series RCA Y-Adapter Cable
What Is It: A one male to two female Y-adpater cable - for splitting an RCA audio output signal.
  • Suitable for digital audio or subwoofer connections.
  • Short cable adapter for easy installation
  • Pro-grade connectors and build quality
  • You'll need to buy extra RCA cables for each connection.

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 connection.

Like the one above, a Y-cable can also be used for connecting two subwoofers to an AV receiver with a single subwoofer output.

Can You Convert Coaxial Digital Audio to RCA Analog Stereo?

So, here’s the thing. You have a digital coaxial output on your Blu-ray player – however, you only have stereo RCA inputs on your amplifier.

How will you hear the audio from your movie on your speakers?

Like the model pictured below, the solution is to buy a coaxial digital audio-to-analog RCA converter.

This device will accept either a coaxial or optical digital audio signal and output it as stereo analog audio.

This converter can be used anytime you need to convert S/PDIF digital audio to analog stereo audio – and it even has an internal volume control.

If you want to send movie audio to a stereo speaker system, then a converter like this can make this a simple process.

An advantage of this device is it accepts more audio formats than most converters. You can send stereo PCM audio from your TV or disc player – or it even decodes 5.1 Dolby Digital and DTS.

Many converters will only accept a digital PCM audio signal. While this is OK for some devices, many digital audio outputs only support Dolby Digital or DTS audio.

Of course, if you only need PCM audio, then you can get a cheaper converter that doesn’t have built-in decoding.

How Do You 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.

For example, you might have an old tape deck with stereo analog outs that you want to connect to your speaker system or soundbar with only coaxial digital audio inputs.

In this case, you will need to buy an analog RCA to digital coaxial audio converter.

Top Analog to Digital Audio Converter
Musou RCA Analog to Digital Audio Converter
What Is It: An adapter that converts an analog stereo audio signal to optical or coaxial digital audio.
  • Supports uncompressed 2-channel PCM/LPCM stereo audio
  • Converts to S/PDIF coaxial or TOSLINK optical audio
  • Sampling rate: 48 kHz
  • Not bi-directional - analog to digital only.

With the converter pictured above, you would connect the stereo analog audio output from your tape deck to the RCA inputs.

Then, connect a digital audio coaxial cable from the output to your amplifier or soundbar.

This device also has the advantage of supporting an optical audio output too.

Frequently Asked Questions

Here are some quick answers to popular questions about coaxial digital audio:

What Is a Digital Audio Coaxial Cable?

A coaxial cable for digital audio transfers S/PDIF stereo and multichannel audio between devices. It has a male RCA connector at each end, a coaxial build and a 75-ohm impedance rating for the cable and connector.

What Is the Coaxial Output on a TV?

The coaxial output on a TV is for sending digital audio. You would use it to connect the sound from your TV to a speaker system or soundbar.

What’s the Maximum Length of a Digital Audio Coaxial Cable?

While there is no specified limit, a well-built cable should transmit digital audio up to 50-feet (15 meters) – and maybe more. However, much will depend on the construction of the cable and the electronics in the source and destination devices. As with most audio cables, it’s usually best to keep the length to a minimum.

What’s the Difference Between a Coaxial and Optical Digital Audio Connection?

In many ways, coaxial and optical digital audio connections are very similar. They both transmit S/PDIF digital audio and support uncompressed stereo PCM audio and compressed 5.1 DTS and Dolby Digital audio. The main difference is the connector and cable. While TOSlink optical audio uses thinner optical fiber cables, coaxial digital audio is sent with 75-ohm coaxial cables, which are more robust over a longer distance.

Can You Use an RCA Cable for Coaxial Audio?

Firstly, a standard coaxial digital audio cable is an RCA cable because it uses RCA connectors. However, the question is more likely, can you use the cheap RCA cables that come with your DVD player or TV for digital audio? The answer is yes. Although cheap RCA cables are unlikely to be coaxial and rated at 75-ohm, they will work in most cases – although probably only over a short distance. However, to be sure of a good signal, it’s best to buy a 75-ohm coaxial cable.

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About The Author

Paul started the Home Cinema Guide to help less-experienced users get the most out of today's audio-visual technology. He has been 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. You can find out more here.

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