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Routing Configurations for Two MOTU AVB Audio Interfaces

The heart of each AVB interface is its built-in Routing Grid. It's the internal patch bay which links the on-board 48-channel digital mixer, To and From Computer audio streams, and the physical input and output jacks on the body of your interface.

For signal from any source to reach any destination, attention to the AVB Routing Grid is imperative, especially when working with two or more devices on the same AVB network.

To maximize your AVB interface's potential, users should be Routing Grid masters. If the system is new to you, or you still need to round out your skills, read this article first for an in-depth look at the MOTU AVB Routing Grid. Once the basics are mastered, this document will provide insight on the theory behind routing signal between two AVB audio interfaces.

This document will use both the 16A and the 24Ai as examples, however the same theory can be applied to any two MOTU AVB interfaces.


When using multiple MOTU AVB audio interfaces, there are two major considerations to keep in mind, Clocking and Routing. The remainder of this article will discuss routing, however, correct clocking should be established initially.

Note: Correct clock sync is required when using any two audio interfaces together, not just MOTU AVB interfaces.

There are a variety of clocking options and scenarios available to the MOTU AVB devices, however when using two AVB interfaces, achieving sync through the Network connection is preferred.

Connect the two units directly to each other with a Cat-5e or Cat-6 cable. In most cases, one unit would be connected directly to the computer, and the second unit is only connected to the first via this network connection (aside from its audio connections).

In this setup it is generally assumed the 16A would be the device that is connected to the computer (via ThunderBolt or USB), and the 24Ai would be connected to the 16A with the Cat-5e or Cat-6 cable. In this case, standard workflow would find the 16A to be the master unit, and the 24Ai to be the slave unit (although the opposite is possible).

Access the 16A through the MOTU AVB Web App as shown to the right, and view it's Device tab pictured on the bottom left. Along the left-hand column of the pictures below, you will see both the 16A and the 24Ai listed under "Devices", and an indication that the 16A is selected. The fastest way to achieve sync, is to click the Become Clock Master button in the Clocking section of the 16A's Device tab (outlined in red on the left). The clock status light will blink, and settle with a grey/white icon.

The clock mode for the 16A will be set to Internal. If you toggled over to the 24Ai's Device tab, you will notice it's clock source is set to the 16A, (as shown on the right).


Once sync is established, it is time to route signal. From here, steps may vary based on your specific workflow and goals, but a common scenario is to record input signal from both devices in your DAW at the same time.

For the purposes of this document, we will record 24 analog inputs from the 24Ai, and 16 analog inputs from the 16A.

The first step is to route the 24Ai's input signal to the 16A. Click on the 24Ai button on the left-hand column of the MOTU AVB Web App, and visit its Device tab. Scroll down and enable 3 AVB Output Banks in the AVB Stream Setup section, as shown below.

Each bank carries 8 independent audio streams, so three banks covers all 24 analog input channels on the 24Ai. You do not need any AVB input streams enabled for the 24Ai, (as no signal in this example will be sent back to the 24Ai via AVB).

If you are only recording analog inputs, you can disable the Optical Input banks in the Input Banks section, and all Output banks in the Output Banks section to conserve resources (and improve efficiency), as shown below. You also do not need any Mixer Input channels, To Computer or From Computer audio streams enabled; all three can be set to 0.

Pro-Tip: Disabling unnecessary elements in the Device tab will help keep your Routing Grid concise and organized.

Once done, switch over to the 16A's Device tab by clicking the 16A button on the left-hand column, and scroll down to the AVB Stream Setup section. Here, enable 3 AVB Input Banks. Once done, an AVB Stream Connections section will appear, asking you to match which AVB stream on the network will feed each of the 16A's AVB input banks.

Manually connect each stream sequentially, as you will see the 24Ai's three AVB output streams as options; set Input Stream 1 to 24Ai:1, Input Stream 2 to 24Ai:2, and Input Stream 3 to 24Ai:3. You do not need to enable any AVB output banks.

Just like on the 24Ai, disable the Optical Input and Output banks in the Input Banks and Output Banks section for the 16A. You may want to keep the Analog Output bank enabled so you can send your full mix to your speakers connected to the 16A for playback.

Scroll down to the bottom of the Device tab where you'll find the Computer Setup section. You will be recording 40 independent audio tracks in your DAW, so enable 40 To Computer audio streams. This provides 40 discrete audio streams from your 16A to your computer. Enable 2 From Computer audio streams so you can hear playback via the 16A's Analog outputs. You can set the number of Mixer channels to 0.

Now that Device Tab setup is done, it is time to view the Routing Grid.

Swing back over to the 24Ai, and view it's Routing tab. If you followed the exact Device Tab setup as described above, the routing will be quite easy; you should only see one input bank across the top (Analog Input), and three output banks across the left (3 banks of 8 AVB output streams). Expand all four banks (if they aren't already) so you are viewing the full 24 by 24 gird.

Click at the intersection of Analog 1 and AVB Stream 1 1, and drag diagonally down and to the right (south-east) to the intersection of Analog 24 and AVB Stream 3 8 (the 24th output stream). This routes each analog input on the 24Ai to its own AVB output stream which will feed the 16A.

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Jump back over to the 16A's Routing tab. Here, you should see five input banks across the top, and two output banks on the left if previous Device tab setup was followed exactly.

(Notice how the three AVB input bank names across the top have assumed the name of their connected streams; instead of reading AVB Stream 1, AVB Stream 2, AVB Stream 3, they are named appropriately 24Ai:1, 24Ai:2, 24Ai:3).

Expand the Analog Input bank across the top, and the To Computer output bank on the left. Click at the intersection of Analog 1 (input) and To Computer 1, and drag diagonally down and to the right (south-east) to the intersection of Analog 16 (input) and To Computer 16. This step routes the analog inputs on the 16A to the first 16 audio streams being sent to your DAW.

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With the To Computer output bank still expanded, expand the three AVB Input banks (24Ai 1-3) across the top. Click at the intersection of 24Ai:1 1 and To Computer 17, and drag diagonally down and to the right (south-east) to the intersection of 24Ai:3 8 and To Computer 40. This step routes the 24Ai's analog inputs (which have been sent to their own AVB audio streams) to the 17th-40th To Computer streams being sent to your DAW.

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From here, by assigning these successive inputs (1-40) to audio tracks in your DAW, you are able to record signal from both units simultaneously.

In order to hear playback of your recorded signal, return to the 16A's Routing tab. The From Computer input bank across the top brings your DAW (and system audio) playback into the AVB's routing grid, (hence considered inputs), making it available to be sent anywhere on the AVB network. Route From Computer 1-2 to the Analog Output pair your speakers are connected to, likely Analog Out 1-2.

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To make things easier, you can download the preset files for this setup, and import them directly to your MOTU hardware. Get the 16A preset file here and the 24Ai preset file here. To import these files in your hardware, download them from the available links and use the following instructions:

  1. Open the AVB Web Application.
  2. Select the Device page for the device you want to add a preset file for.
  3. Select the preset icon in the top-left corner of the Device tab.
  4. Select the "Import" button under the "Manage Presets" sections.
  5. Navigate to your downloads folder and select the matching ".avbpreset" file and hit "Open".

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