Applies to all Focusrite audio interfaces with ADAT inputs and outputs compatible with Scarlett or Saffire Mix Control

Many Focusrite audio interfaces feature digital I/O to expand the inputs and outputs available. Compatible Focusrite interfaces feature a combination of S/PDIF and ADAT inputs and outputs.

ADAT uses the TOSLINK optical connection and transmits up to eight channels of audio and a clock signal.

S/PDIF uses both RCA coaxial and TOSLINK optical connections and transmits two channels of audio and a clock signal. Support for optical S/PDIF varies based on the interface. Check the user guide for your device for more information.

Consider the following factors before expanding an interface with digital IO:

• The host
• The expander
• Sample rate
• Clocking

What device is the host?

The host is the device you physically connect to your computer. This is the device you select in your DAW.

The host device doesn't have to be clock leader and can sync to an external clock source.

What device is used for expansion?

The expansion device connects to the host to expand the inputs and outputs. Expansion devices can be a dedicated device, like an OctoPre, or another audio interface you configure in a standalone mode. You can configure all Focusrite audio interfaces with ADAT outputs as expansion devices. Not all interfaces from other manufacturers can be configured as an expansion device.

The expansion device doesn't have to be a clock follower and can be the clock leader.

What sample rate should the system you use?

When synchronising multiple digital audio devices, the sample rate needs to match across all devices. The sample rate also affects how many audio channels you can transmit over the ADAT connection.

• At single-band sample rates (44.1kHz/48kHz), one ADAT connection transmits eight audio channels.
• At dual-band sample rates (88.2kHz/96Hz), one ADAT connection transmits four audio channels.

In most cases, Focusrite interfaces, disable ADAT expansion at quad-band sample rates (176.4kHz/192kHz).

Focusrite interfaces support RCA coaxial S/PDIF at all sample rates. Optical S/PDIF support varies based on the interface and sample rate. Check the user guide for your device for more information.

To learn more about sample rate see Sample Rate, Bit Depth, and Buffer Size Explained

What device is the clock leader?

Digital audio equipment uses a clock to synchronise when each sample starts. In a digital system with multiple devices, all the devices must have the same common clock source. This ensures each sample starts at the same time for each device and, along with matching sample rates, lets the devices synchronise correctly.

You can transmit clock in several ways; this includes 

• Word Clock via BNC
• ADAT via optical port
• S/PDIF via RCA or optical port

All other digital audio devices used are clock followers and sync to the clock leader.

Expansion Setup

This article teaches you how to configure a host and expansion device in Mix Control. If the interface you’re using is not compatible with Mix Control, see the articles below.

How to use the digital inputs and outputs to expand my interface using Focusrite Control 2

How to use the digital inputs and outputs to expand my interface using Focusrite Control

ADAT and S/PDIF are universal protocols — you are able to use ADAT/ S/PDIF devices from other manufacturers to expand your Focusrite interface or your Focusrite interface to expand other audio interfaces. See the documentation for the device you’re using to configure it.

1. In Mix Control, go to the Device Status section.

2. Set the sample rate of the setup.
3. Set the sync source for the setup.
   • If the host is the clock leader, set the sync source to internal.
   • If the host is a clock follower, set the sync source to the external clock source used.

If expanding the outputs of your interface, you will need to route the desired host outputs to the S/PDIF or ADAT outputs.

In the routing section, set ADAT Outputs 1-8 to additional playback channels to increase the outputs from your DAW as shown below. This is ideal for connecting outboard equipment or a mixer. 

Or

Set ADAT Outputs 1-8 to a mix; this is ideal for creating extra headphone mixes for artists with near 0 latency.

1. In Mix Control, go to the Device Status section.

2. Set the sample rate of the setup.
3. Set the sync source for the setup.
   1. If the expansion device is the clock leader, set the sync source to Internal.
   2. If the expansion device is a clock follower, set the sync source to the external clock source used.
4. In the routing section, set ADAT outputs 1-8 to analogue inputs 1-8.

If expanding the outputs of your interface, you will need to route the ADAT inputs to the analogue outputs.

5. In the routing section, set analogue outputs 1-8 to ADAT inputs 1-8.

Below you can find a few example setups that show specific instructions and settings for each setup. Use these examples to help configure specific setups.

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