Applies to all Focusrite audio interfaces with ADAT inputs and outputs compatible with Focusrite Control 2

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 Focusrite Control 2. If the interface you’re using is not compatible with Focusrite Control 2, see the articles below.

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

How to use the digital inputs and outputs to expand my interface using Mix 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 Focusrite Control 2, go to More Options > Preferences > Sample rate & clocking to open this window:

2. In box 1, set the sample rate.
3. In box 2, set the clock source.
   • If the host is clock leader, set the clock source to Internal.
   • If the host is a clock follower, set the clock source to an external clock source.
4. In box 3, set the Digital Port mode.
   • If connecting a single ADAT input or output, use RCA S/PDIF.
   • If connecting two ADAT inputs or outputs, use Dual ADAT.
   • If connecting an Optical S/PDIF source, use Optical S/PDIF

If you're expanding the outputs of your interface, route the host's outputs to the S/PDIF or ADAT outputs.

1. In Focusrite Control 2, click the routing tab.
2. In the Digital outputs,
   • Set the source to a playback channel to increase the outputs from your DAW, this is ideal for connecting outboard equipment or a mixer.

Or

• Set the source to a mix; this is ideal for creating extra headphone mixes for artists with near-zero latency.

1. In Focusrite Control 2, go to > Preferences > Sample rate & clocking to open this window:

2. In box 1, set the sample rate.
3. In box 2, set the clock source.
   • If the host is clock leader, set the clock source to Internal.
   • If the host is clock follower, set the clock source to an external clock source.
4. In box 3, set the Digital Port mode,
   • If connecting a single ADAT input or output, use RCA S/PDIF.
   • If connecting two ADAT inputs or outputs, use Dual ADAT.
   • If connecting an Optical S/PDIF source, use Optical S/PDIF.

If you are using a 4th Generation Scarlett interface, you can use the ADAT expansion mode in Focusrite Control 2 to automatically configure the routing for ADAT. To access this, go to More Options Preferences Device and select ADAT Expansion

5. In Focusrite Control 2, click the routing tab.
6. In the Digital Outputs, set the ADAT output sources to the Analogue Inputs.

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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