Friday, August 18th, 2017

Review of the MOTU AVB equipped 16A Audio Interface

By editorJuly 30, 2017


MOTU have been very busy over the last few years introducing a significant number of new audio interfaces employing the very latest in high speed, high capacity audio streaming and networking.

Being the owner of two of their Ultralite audio interfaces and having an increasing number of analogue outboard units in my home studio setup, I decided to have a look at the MOTU 16A interface which offers a massive 16 balanced analogue inputs and 16 balanced analogue outputs, plus a pair of 8 channel ADAT optical ports, all in a mains powered 1RU x 19” unit.

The 16A is one of a new family of MOTU interfaces offering three significant enhancements from previous models.  Let’s have a look at these in detail.

First off, is a move to using Thunderbolt as the primary high speed interconnect to your main computer.  MOTU have at present settled on the Thunderbolt 2 interconnect which offers data transfer rates up to 20 Gbit/s, which in the MOTU application means up to 256 channels of I/O down a single cable.

Why would you want such a high I/O capability?  Well imagine a studio set up with three 16A units, so that’s 96 channels of analogue I/O plus all the ADAT, so you can begin to see how the total number of channels can add up.  And how about live stage applications?  With a large number of cable and radio mics, all coming to a stage based mic amp/A-D converters, and performer foldback mixes coming back, all ‘connected’ to the rear of stage mixing position, via a single CAT5e network cable.  This is a system with huge potential.  Okay, we’ll get to where CAT5e comes in, in a moment.

Don’t panic if your recording setup is PC based with no Thunderbolt.  MOTU still includes a USB2 connection which (I’m assured by the tech guys at MOTU) will handle the full I/O of a single 16A.

Secondly – so what about this mention of CAT5e networking cable?

This new family of MOTU interfaces are all able to work with the AVB standard.  AVB stands for the IEEE 802.1 ‘Audio Video Bridging’ Ethernet standard for high-bandwidth, low-latency audio streaming over Ethernet.  This allows you to build a network of audio interfaces and controllers, all working to the AVB standard and connected via standard Cat-5e network cable.  The entire network operates to near zero latency even over very long cable runs.  In practice, this allows you to stream hundreds of audio channels between audio interfaces and to and from host PCs (for recording) even at high audio sample rates.

However the AVB standard is not limited to routing audio, it can also bring additional audio controllers into the network, both wired via standard Cat-5e network cable to an AVB connected network point or wirelessly.  So now you can manage a large network of MOTU audio interfaces, all from an iPad.  Is that cool?  Of course it is.

Although it is possible to connect from a suitably equipped computer to a single MOTU interface via AVB and Cat-5e cable, in a multi-interface set up, the first connection from the computer to the AVB network is done via Thunderbolt.  Then each of the MOTU interfaces has an AVB port which allows either:-

A second MOTU interface to be daisy-chained to the first unit, via a standard Cat-5e network cable, or a connection to a MOTU AVB 5-port data hub.  By this means, a flexible network of audio interfaces and control devices (e.g. multiple computers, iPADS, even iPhones!) can be connected.

This allows any audio analogue or digital source to be connected to any analogue or digital destination within the network.

Let’s have a look at the unit’s front and rear panels in detail.

About half of the front panel is taken up with level metering for the analogue and optical I/O.  Just to the right of the metering you get a display of the currently selected sample rate and the clock source.  To the right again is the power switch.

Moving left from the metering, are buttons to navigate through the unit’s extensive menu options.  MOTU have retained the ability to control a chunk of the unit’s set up and functionality from the front panel without having to use the computer based control system.

And finally, to the left again, there’s a button to display network settings for the device, including its IP address.

It’s all very logically laid out and easy to access and view.

Flipping around to the rear side of the unit, we’ve got a total of 32 ¼” balanced jacks for the analogue I/O and a total of 4 ADAT optical “lightpipe” jacks which offer a digital I/O capacity which depends of the sample rate.  So that means 16 channels of 24-bit ADAT at 44.1 or 48kHz and 8 channels at 88.2 or 96kHz.  As is normal, these ADAT ports are disabled at higher sample rates.

Just below the ADAT’s are the triplet of data interconnects, USB2, Thunderbolt 2 and Network.

And importantly, MOTU have included a pair of wordclock BNCs (in and out/through) as would be expected for a unit which may sit within a large master clock equipped network.

And finally a standard IEC mains connector (much preferred to an external wall-wart).

Thirdly, MOTU have been busy upgrading to the latest-generation 24 bit ESS Sabre32 Ultra™ converters, which bring increased dynamic range of 117dB (line in) and 123dB (line out) and a quoted THD+N figure of 0.0003% at -1dBFS, unweighted at 1kHz.

MOTU have also been working very hard on I/O latency which is now down to an impressive 1.4mS from analogue in, through the host (computer), to an analogue out (@96kHz sampling with a 32 sample host buffer).

As with previous MOTU interface units, a screen based control and mixing system is offered.  This has two main components.  Point to point audio routing is done using an X/Y matrix style point and click system.  This allows any input to the routing matrix to be routed to any one or multiple outputs.

Where mixing of inputs is required then a full 48 channel audio mixer is included.  This is not designed to replace your usual DAW software but it is incredibly useful to set up typical low latency foldback mixes for your performers; so in a recording session, it would allow you to combine a stereo foldback feed from the main DAW system (of already recorded material) with a low latency feed of all the additional contributions being recorded.  The mixer is able to generate a total of 12 stereo mixes and each of the 48 channels has a full compliment of EQ, Dynamics and Reverb, all run from a dedicated on-board DSP, so it doesn’t place any additional load on your host computer.

It’s really important to mention that all the router and mixer settings are stored in non volatile memory within the 16A, so you can do all the set up on a Computer and then control ‘live’ from an iPAD, even wirelessly, during the performance or session.

Unlike previous MOTU control software which had to be loaded on to your computer, MOTU have moved to a web based control system, which allows you to control all MOTU AVB equipped interfaces that are connected in the same network.  The MOTU serves the web app from its own internal software.  The use of a web based app means that any web browser equipped device (Mac, Windows, Linus, iOS and Android), can access the entire AVB network via either a wired or wireless connection.  It’s also possible to connect multiple control devices simultaneously.

In a typical small studio set-up you can control the 16A, via local IP address, down the USB2 or via Thunderbolt, without the need for an Ethernet connection.  Where you require wireless control, then the MOTU unit needs to be connected to your local WiFi network which gives any control device on the same network, access to the unit.  Optional password protection prevents unauthorized access from the network.

Audio drivers are provided for Thunderbolt (Mac and PC), and USB audio drivers for Mac (CoreAudio) and Windows (ASIO and Wave).

Although my own requirement is probably never likely to go beyond a couple of 16A’s, the comprehensive network audio and control facilities offered by this new family of AVB equipped units is certain to take MOTU into a whole new market segment, especially into large multi studio facilities and probably more importantly into live arena applications in a big way.

Check out the latest AVB equipped MOTU interfaces here

Robert Campbell
July 2017

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