3 Ways To Use ADAT To Expand Your Audio Interface

Written By Kyle Mathias  |  Audio Gear, Mixing, Recording 

Many audio interfaces have optical ADAT connections. ADAT allows you to expand your I/O beyond the analog inputs and outputs built into the interface. In this video, we will look at three popular ways you can use ADAT to expand your studio.

Sweetwater sent me a Focusrite Scarlett 18i20, a Cranborne Audio 500ADAT, and a few optical cables so that I can walk you through the configuration needed for each setup that I’m about to show you.

Basic Setup, Cabling, & Clock

No matter which equipment you’re using, there are some basic steps you’ll need to follow.

ADAT Optical Cables

First of all, you’ll be using optical cables to connect everything together. One optical ADAT connection can carry 8 channels of audio at up to 48 kHz sample rate or 4 channels of audio up to 96 kHz sample rate. However, both the Focusrite 18i20 and the Cranborne Audio 500ADAT have dual ADAT connections, which means with two optical cables they can facilitate up to 8 channels at 96kHz!

I’ve connected the two outputs of the Focusrite Scarlett 18i20 to the two inputs on the Cranborne Audio 500ADAT and vice versa, but this doesn’t give me the ability to route 16 channels each way, as you might expect because the ADAT protocol is limited to 8 channels. 

The device sending the signal through its output will emit a light that travels through the fiber optic cable and into the input of the receiving device. You can actually see the light emitting from the end of the cable when an output device is connected.

It’s very simple – connect the output of the sending device to the input of the receiving device. That’s a lot easier than connecting these two devices with analog cables!

ADAT Clocking

Once you’ve got the cables connected, you’ll need to set up the clocking between these two devices. Because this is a digital connection, it’s critical that the two devices stay in sync with each other while passing digital audio signals back and forth.

There’s a clock built into both devices, but there can only be one primary clock. So, we need to set up one device as the primary clock, or master clock, that the secondary device will follow.

This part is very important, so read closely… If you’re only making one connection with ADAT, the sending device needs to be the primary clock because ADAT is not bidirectional. However, if you’ve got an ADAT loop (with the output of each device connected to the input of the other), either device can be the primary clock. 

In the case of a loop, I’d recommend picking the device that has superior clocking technology. The clocking in the Focusrite interface is very good, but the Cranborne Audio 500ADAT has extremely low-jitter clocking. So, I’ll set up each device to follow the 500ADAT as the master clock.

Let’s start with the 500ADAT. We need to turn on the correct dip switches on the back…

Do we want to receive clock information from the ADAT connection? No. That would mean it would follow the device connected to its ADAT input. 

Do we want to receive clock information from the wordclock connections? No. We won’t be using these connections in this particular scenario.

What we want is for the 500ADAT to follow its internal clock, so let’s flip the “Internal” dip switch to the “On” position. We also need to set the sample rate. I’m going to use 48kHz in this case.

Next, with the Focusrite interface connected to my computer, I’ll open up the Focusrite Control software and select the gear icon in the top left corner. I’ll set the clock source to “ADAT”, so it follows the clock information coming from the 500ADAT. And I’ll also set the sample rate here to 48kHz.

1) More Inputs With ADAT

The first way to use ADAT to expand your audio interface is to add more input channels.

Maybe you have an audio interface with only 2 microphone preamps, but you want to record a full band with several microphones. If your interface has an ADAT input, you can connect an external microphone preamp via ADAT to add more channels.

Of course, you’ll need an external mic preamp that has ADAT outputs in order to do this, such as the Focusrite OctoPre or a Cranborne Audio 500ADAT with a few preamp modules. Let me show you an example…

Let’s say I’ve already used the 8 microphone preamps on my Focusrite Scarlett 18i20 but I need two more. I can route two Camden preamps (within my 500ADAT chassis) into my interface through ADAT. Remember, we’ve already got the output of the 500ADAT connected to the input of the Focusrite interface.

Before we proceed, we need to open up the manual for the Focusrite 18i20 to determine which digital inputs in the DAW correspond with each ADAT input within the interface. Because the Camden preamps are in slot 1 and 2 of the 500ADAT, we will be looking for ADAT 1.1 and 1.2. It looks like ADAT 1.1 and 1.2 correspond to Digital In 3 and 4. So, let’s select Digital In 3 and 4 so that these preamps are routed to these tracks.

Of course, if you were using a Focusrite OctoPre or a fully loaded 500ADAT, you could use all 8 channels through a single cable! 

The added benefit here is that the superior analog to digital converters in the 500ADAT are being used for these two channels. That’s because the analog signal from the microphone is converted within the chassis and sent digitally to the interface to be recorded.

I also want to mention that additional ADAT inputs aren’t just useful for microphone preamps – mixers and other audio devices commonly have ADAT outputs that you can bring in with your ADAT-enabled interface.

2) More Outputs With ADAT

The second way to expand your interface with ADAT is by adding more outputs. There are a few reasons why you might want to do this… 

First, you might just simply need more outputs for creating multiple headphone mixes, feeding a second pair of monitors, or routing audio to an audio recorder with ADAT inputs. 

But the second reason might be less obvious at first glance. Think back to when I said the analog to digital conversion would take place within the device sending the ADAT signal to the interface. Well, the opposite is also true. Instead of using the digital to analog converters within my Focusrite Scarlett 18i20, I can use the far superior converters within the Cranborne Audio 500ADAT for my monitors. 

Again, the Focusrite Scarlett 18i20 (and most modern audio interfaces) have converters and internal clocks that are more than capable of producing professional records, but why not use the best converters that you have access to, right? 

With the ADAT output of my interface connected to the ADAT input of the 500ADAT, let’s set this up so that signal sent to my monitors is converted from digital to analog by the 500ADAT rather than the Focusrite 18i20.

I’ll go ahead and connect my monitors to the Mix Outputs on the back of the 500ADAT. Then, I’ll open the Focusrite Control software that comes with the 18i20 interface. I’m going to navigate to the ADAT outputs at the bottom of this list. Because slots 7 and 8 on my 500ADAT are empty, let’s use those for converting the signals that will be sent to my monitors.

If I wanted to use each ADAT output channel separately, I could toggle this “Stereo” button. In this case, I want to use these outputs as a stereo pair. So, I’ll leave the “Stereo” button engaged.

Now that ADAT outputs 1.7 and 1.8 are sending the monitor signal from the interface to the 500ADAT, I can use these “Mix Level” and “Pan” knobs along the bottom of the 500ADAT to bring up slots 7 and 8 in the mix.

And there we have it. I can hear the monitor output of my Focusrite interface playing through the monitors, converted to analog by the superior converters within the Cranborne Audio 500ADAT.

3) Inserts With ADAT

The third way to use ADAT in your studio is to set up inserts for outboard FX like analog EQs, gates, and compressors.

In order to do this, we will be using a connection from the Focusrite 18i20 to the Cranborne Audio 500ADAT as an insert send as well as a connection from the output of the 500ADAT back into the 18i20 as an insert return.

Let’s take a look at what this would look like inside the DAW. In Reaper, I’ll add the ReaInsert plugin to my bass track. This is going to create a point in the signal chain that goes out of the interface, through my dbx compressor module, and back into the interface where it continues along its normal path.

The dbx compressor is in slot 3 of the 500ADAT. So we will be using ADAT 1.3 for the insert send and return. This time, I’m going to unlink ADAT 1.3 and 1.4 so that I can use 1.3 independently.

Again, we can either check the manual for which DAW outputs correspond to ADAT Output 1.3, or simply verify which Playback output is routed to ADAT Output 1.3 by checking the Focusrite Control configuration. It looks like ADAT 1.3 is currently set to output Playback 15. I’ll select Output for my Insert send to Output 15.

The Digital Input that corresponds to ADAT 1.3 is Digital In 5. So, that will be the insert return channel in the ReaInsert plugin.

Now, at this point in the signal chain, the signal goes to the 500ADAT, gets converted to analog, passes through the dbx compressor, gets converted back to digital and continues along the signal path within the DAW.

I want to thank Sweetwater again for sending this 500ADAT and Scarlett 18i20 – I’ve really enjoyed the flexibility they’ve added to my studio!

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