Using AVB Ethernet to connect to a Mac

Using your MOTU AVB device as a Mac audio interface over AVB Ethernet

When operating as an audio interface, MOTU AVB devices can be connected to a Mac with USB or Thunderbolt (if available). With firmware update 1.2.5 or later, and OS X El Capitan (10.11) or later, a third option is available: AVB Ethernet.

With affordable cable runs that can be substantially longer than USB or Thunderbolt, Ethernet allows you to position your MOTU interface much farther away from your Mac, across the room in a machine closet with other gear, for example, or in an isolation booth down the hall, near microphones and musicians. Using Ethernet frees up the USB and Thunderbolt port(s) on the Mac for displays and other devices. Ethernet also opens up your Mac to the world of audio networking, where you can connect multiple devices to create a unified network. You can then stream hundreds of audio channels over the network with very low latency, from any device or computer to any other.

To use AVB Ethernet, all you need is a recent Mac (any Mac that has a Thunderbolt port on it) with Mac OS X El Capitan installed. Connect the network port on your MOTU interface to the Ethernet port on the Mac using a standard, high-grade (CAT-5e or CAT-6) network cable up to 100 meters in length. You can then use your MOTU device as a standard multi-channel audio interface with any Core Audio compatible host software running on the Mac.

NOTE #1: if your Mac doesn't have an Ethernet port, you can connect your MOTU interface via Ethernet using a Thunderbolt-to-Ethernet adapter. Ethernet might be preferable over Thunderbolt because the Ethernet cable can be up to 100 meters long, using standard Ethernet cabling (which is very affordable).

NOTE #2: USB-to-Ethernet adapters cannot be used because the Mac's USB chip set does not support AVB Ethernet.

Setup

1. Connect your MOTU AVB interface Network port to the Mac's Ethernet port, or connect both devices to an AVB Switch and power it on.

• Please note when connecting devices or restarting your system, AVB devices may become acquired by the Network Device Browser in Audio MIDI Setup. You must deselect each connected AVB device in this window in order to use Mac Virtual Entity Mode.

2. Launch the MOTU AVB Discovery app. From the Settings menu (circled in red below), choose Launch Mac Virtual Entity, and from the sub-menu choose the Ethernet port to which your MOTU AVB interface is connected. It should now be checked.

3. After completing step #2 above, the Mac will appear in the AVB device list in the MOTU AVB web app, as shown below. PLEASE NOTE: it may take several minutes for the Mac to appear in the list, the first time you set this up. After the first time, though, you won't experience any delays.

4. From the Configuration menu, choose the channel mode that best fits your workflow. NOTE: MOTU interfaces currently only support 8-channel streams (or less) so be sure to avoid configurations with streams that have more than 8 channels.

5. From the Sample Rate menu, choose the desired sample rate. Currently, the Mac only supports 48, 96 and 192 kHz sample rates.

6. For Playback from the Mac, go to the Device tab for your MOTU interface (the 1248 in the example below), and connect the input streams to the Mac’s output streams.

7. In the Routing tab, route the Mac’s output streams to desired physical outputs on your MOTU AVB interface.

8. For Recording to the Mac, route desired physical inputs on your MOTU AVB interface to output streams.

9. On the Mac’s Device tab, connect the Mac's input streams to the MOTU interface’s output streams.

NOTE: Leave Media Clock Input Stream set to None. (This setting can be used to sync the Mac to certain 3rd-party AVB devices that support Media Clock. This setting is not needed for MOTU devices.)

Clocking

In the example above, the 1248 is the clock master and the Mac is clocking to 1248’s Output Stream 1. You can also reverse this scenario, where the Mac becomes the master and 1248 clocks to Mac’s Output Stream 1. NOTE: the Mac does not follow the web app's Become Clock Master button, so you must set the Mac's Clock Mode manually.

AVB stream and channel counts

Each MOTU AVB stream is a group of 8 audio channels. While testing is on-going, OS X AVB performance varies with different Mac models. Models such as the Mac Pro (late 2013) are able to handle 8 streams (64 channels) in and out simultaneously, for MOTU interface models that support 8 streams. (Check motu.com/avb for a summary of supported stream counts for each MOTU interface model.) For older Macs, we recommend one or two streams in each direction. Generally speaking, it is best to enable only as many streams as you need.

If you need to change the number of audio channels or streams, we recommend that you temporarily disable the device in the Network Device Browser first, before making any stream or channel count changes. This is because some host software applications have trouble if you change the channel count while the device is still enabled.