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

  • Updated

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

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Focusrite Control 2 and its remote control mobile app now support Scarlett 3rd Gen, Clarett+, Clarett USB, and Scarlett 2nd Gen (6i6, 18i8, and 18i20) — if you're having issues with Focusrite Control, we recommend upgrading to Focusrite Control 2 if your operating system is supported.

Thunderbolt Claretts aren't supported with Focusrite Control 2 or the Focusrite Control 2 mobile app.

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.

ADAT Setup

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

Host setup

  1. In Focusrite Control, click the settings cogwheel to expose the settings tab as shown below.
  1. Using the Sample Rate drop down menu, set the sample rate of the setup.
  2. Using the Clock Source drop down menu, set the clock source for the setup,
    • If the host is the clock leader, set the clock source to internal.
    • If the host is a clock follower, set the clock source to the external clock source used.
  3. Using the drop down menu, set the Digital I/O 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 expanding the outputs of your interface, you need to route the desired host outputs to the ADAT outputs.

  1. In Focusrite Control, click the output routing tab at the top of the screen.
  2. Scroll through the outputs list to find ADAT outputs 1-8,
    • 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 custom mix; this is ideal for creating extra headphone mixes for artists with near 0 latency. On Scarlett 18i20 3rd Gen, if you want to communicate with your artists through the built-in talkback microphone, use the Custom Mix + Talkbox option.

Expansion device setup

  1. In Focusrite Control, click the settings cogwheel to expose the settings tab as shown below.
  1. Using the Sample Rate drop down menu, set the sample rate of the setup
  2. Using the Clock Source drop down menu, set the clock source for the setup
    1. If the expansion device is the clock leader, set the clock source to internal.
    2. If the expansion device is a clock follower, set the clock source to the external clock source used.
  3. Using the drop down menu, set the Digital I/O mode.
    1. If connecting a single ADAT input or output, use RCA S/PDIF.
    2. If connecting two ADAT inputs or outputs, use Dual ADAT.
    3. If connecting an Optical S/PDIF source, use Optical S/PDIF.
  4. In Focusrite Control, click the output routing tab at the top of the screen.
  5. Scroll through the outputs list to find ADAT outputs 1-8,
  6. Set the source to Hardware Input > Analogue 1-8 to route the inputs on the interface through to the ADAT output.

If you are also expanding the outputs of your interface, the ADAT inputs need to be routed to the analogue outputs.

  1. In Focusrite Control, click on the output routing tab at the top of the screen.
  2. Scroll through the list of outputs to find Line Outputs 1-8,
  3. Set the source to Hardware Input > ADAT 1.1 > 1.8
  4. In the settings tab, set the Monitor Controls to none. This prevents the monitor dial from affecting the output level.

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.

Example setups

18i8 3rd Gen and OctoPre

This example shows how you can connect a Scarlett 18i8 3rd Generation and an OctoPre for eight additional inputs. In this setup, the OctoPre will be the clock leader and runs at 48kHz.

  1. Connect the ADAT output on the OctoPre to the ADAT input on the 18i8.
  2. On the front panel of the OctoPre, set the clock source to internal and the sample rate to 48kHz.
  3. Open Focusrite Control and click on the settings cogwheel to expose the settings.
  4. Set the Sample rate to 48kHz, the Clock Source to ADAT and the Digital port mode to ADAT.

18i20 3rd Gen and OctoPre SMUX for dual band sample rate

This example shows how you can connect a Scarlett 18i20 3rd Generation and an OctoPre using SMUX to run at dual band sample rates. In this setup, the OctoPre will be the clock leader and will run at 96kHz.

  1. Connect ADAT output 1 on the OctoPre to the ADAT input 1 on the 18i20.
  2. Connect ADAT output 2 on the OctoPre to the ADAT input 2 on the 18i20.
  3. On the front panel of the OctoPre, set the clock source to internal and the sample rate to 96kHz.
  4. Open Focusrite Control and click on the settings cogwheel to expose the settings.
  5. Set the Sample rate to 96kHz, the Clock Source to ADAT Port 1 and the Digital port mode to Dual ADAT.

Clarett 8PreX 16 channel ADAT Input and Output with two Clarett+ OctoPres

This example shows how you can connect two OctoPres to a Clarett 8PreX for 24 inputs and 26 outputs. In this setup, the Clarett 8PreX will be the clock leader and will run at 48kHz.

  1. Connect ADAT output 1 on the first OctoPre to ADAT input 1 on the 8PreX.
  2. Connect ADAT output 2 on the first OctoPre to ADAT input 2 on the 8PreX.
  3. Connect ADAT input 1 on the first OctoPre to ADAT output 1 on the 8PreX.
  4. Connect ADAT input 2 on the first OctoPre to ADAT output 2 on the 8PreX.
  5. On the front panel of both OctoPres, set the clock source to ADAT, the sample rate to 48kHz and enable ADAT > Line.
  6. Open Focusrite Control and click on the settings cogwheel to expose the settings.
  7. Set the Sample rate to 48kHz, and the Clock Source to internal.
  8. Navigate to the output routing tab and set the ADAT outputs 1.1-2.8 to additional playback channels.

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