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How to Use SPDIF on Audio Interface: Connecting Your Devices

How to Use SPDIF on Audio Interface_ Connecting Your Devices

Whether you need more inputs or outputs or collaborate with another audio producer with a custom setup, knowing how to connect audio interfaces and sync their SPDIF clocks is always useful. 

Unlike analog audio, digital audio runs on a clock. So you need to be able to sync them to avoid having errors in your audio. 

In this article, we’ll walk you through how to sync both audio interfaces using SPDIF.


  • Using more than one audio interface is possible and easy to set up!
  • Sound signals are converted and transmitted at regular intervals within split seconds
  • Using more than one audio interface cause the signals to be out of sync with each other and disrupt your work
  • SPDIF digital clocking solves this by giving your devices the same timing information
Table of Contents

How to Connect Your 2 Audio Interfaces

Here are the steps to connect two audio interfaces properly:

Step 1: Set Your Primary Device

First, you must ensure that both audio interfaces have SPDIF connections. Next, choose which audio interface will be the primary and slave devices. 

Step 2: Connect Them Both

Now you need to connect one end of your ¼-inch RCA cable to the output plug of your primary device. 

Then, connect the other end of the same cable to the input plug of your slave audio interface.

How to Use SPDIF in Your Audio Interface

Here is the way to use SPDIF for any of your audio interfaces!

Step 1: Connect Your 2 Audio Interfaces to SPDIF

After connecting them both on your computer, open their respective DAWs.

Step 2: Setup the DAWs

Then, proceed to the setup menu and select the SPDIF clock option on both DAWs. 

Next, set your sample rate as 48KiloHertz for both devices. You could also set it at 44.1 KiloHertz, but it’s best to set it at the highest.

It’s also perfectly fine to set your audio interfaces at any sample rate you’d like, as long as it’s the SAME SAMPLE RATE FOR BOTH.

Your two audio interfaces are now in sync!

What Is SPIDF?

Sony and Philips developed it. It’s a digital communication of audio postcode modulation sent out as a stereo signal using 1 RCA connection.

An audio interface would have 1 RCA SPDIF out and another RCA as SPDIF in. SPDIF also includes a clock for the sampling rate. SPDIF is most commonly used between a CD player or some other musical instrument and to HiFi system.

At the same time, audio interfaces can also be used as HiFi so that we can connect them. But we can also utilize the clock to synchronize the 2 audio interfaces.


Optical digital uses light to transmit audio through the cable’s optical fibers. Optical is mostly used in homes, with its ability to deliver Dolby Digital and DTS surround sound. 

It’s the more popular connection compared to coaxial, and it can be found in most amplification or DAC end connections.


Coaxial digital uses electricity to transmit audio. It uses a circular RCA connector, the same one used for analog connections. 

It looks similar to a dedicated coaxial digital cable, but you can’t use them interchangeably as they have different impedance values and can cause errors in your work. 

Coaxial is less popular and used by fewer audio producers, so it can’t always be found in devices, especially the new ones. 

Which is Better, Optical or Coaxial?

Coaxial will deliver better sound quality. 

Coaxial has higher bandwidth available, so it can support high-quality audio up to 24-bit/192kHz, while optical can only support up to 96kHz. 

You should always choose coaxial unless you use DAC connections. 

This is because optical can filter noise from the source when it reaches the DAC circuitry, something coaxial can not do.

Other Digital Connection Types

Here are the other digital connection types to look out for!

ADAT Optical

ADAT is the optical audio data transmission type that includes eight digital audio data channels.

It uses the same interconnect as the widely adopted TOSLink two-channel standard.

ADAT optical is popular for digital I/O connection on mixers and recorders.


Also known as Sample Multiplexing, SMUX is for transporting high bandwidth digital audio utilizing lower bandwidth technology.

It’s what you can use to transmit a 96 kHz digital audio stream utilizing S/MUX based on lower sample rates.


Short for Audio Engineering Society or European Broadcasting Union, the AES/EBU is an audio interface used by professionals to transmit digital audio from CD and DVD players to amplifiers.

Despite being unrelated to any sample rate or audio format, AES/EBU is frequently used to transmit PCM and Dolby Digital 5.1.

Frequently Asked Questions (FAQs)

Curious about a few more things? We’ve got you!

How Could We Benefit From S/PIDF Ports?

SPDIF connections transfer digital audio signals from one device to another without the need to first convert to an analog signal, preserving the quality of the audio transmitted.

SPDIF gives you a higher sound quality straight from the source. 

What Is the AUX Mode?

AUX mode is usually used to connect audio devices like phones and tablets directly to your speaker as long as it’s compatible with a 3.5mm AUX output plug.

What Is Digital Clocking?

When audio is transmitted to an audio interface, it has to be converted from analog to digital, then from digital to analog again. 

This conversion in the audio interface takes only a split second. However, when using 2 audio interfaces simultaneously, the sounds can get out of sync. 

This is because the audio has to be sampled at very specific and regularly repeating intervals within those split seconds. 

Digital clocking solves this problem. 

The digital clock of the master audio interface gives the same timing information to both devices so that conversions from analog to digital and digital to analog will always be at the same times and have the same intervals. 


And that’s all we have for connecting more than one audio interface and syncing them using SPDIF!

We hope this article has been helpful in your audio creation work. 

If you have any more questions or tips and tricks that you would like to share, let us know in the comments!

About the author


After becoming obsessed with the beats that were the soundtrack to his youth, Nick became a student of hip hop, digging for vinyl records, looking for the perfect break. Before he got his hands on an MPC sampler, he would mash these records, beats, and breaks into mixtapes and live DJ sets.