Applies to all OctoPres

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.

OctoPre Set Up

This article teaches you how to configure an OctoPre as an expansion device for use with your audio interface. If the interface you’re using is manufactured by Focusrite, see the articles below on how to configure the host.

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

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

1. Connect the ADAT output on your OctoPre to the ADAT input on your audio interface. 
   • When running at dual-band sample rates (88.2kHz and 96kHz), you need two TOSLINK cables to connect the ADAT outputs of the OctoPre to the ADAT inputs of your audio interface
   • If clocking externally via word clock, connect the word clock BNC cable.
   • If your OctoPre also features ADAT inputs, you can connect to the ADAT output of your interfaces to also expand the available outputs.
2. On the front panel, using the sample rate button, set the sample rate of the setup.
3. Using the clock source or sync button, set the clock source.
   • If the OctoPre is the clock leader, set the clock source to Internal.
   • If the OctoPre is a clock follower, set the clock source to an external clock source.

If setting up an OctoPre with a Focusrite audio interface, see the links above for advice on how to set this up, along with some example setups. If using a 3rd party interface, see any documentation for your interface on how to set up an ADAT expansion device such as an OctoPre.

If this article hasn't helped you, please feel free to search again at the top of this page or, to contact support, please click here.