In this article Steve DeMott explains the reasons and method behind his recent decision to switch the tie lines from the keyboard room in his studio from analogue cabling to AVB.

Like most engineers would Steve has been happily using the analogue cabling which was installed in his studio since before his tenure began. Good old fashioned analogue is familiar, ubiquitous and works so most of us don’t see a reason to change until either it no longer works or our needs change. in Steve’s case it was a bit of both at the same time and as it happened the solution was already in his studio, he just needed to figure out how to use it. That answer was AVB. Over to Steve…

In my studio we have 2 isolation booths off of the live room. The bigger of the iso booths we have dubbed “The Keyboard Room,” because it houses the majority of our keyboards. The keyboard room is in the corner farthest from the control room.

The Problem

The issue arose as we thought through connecting the keyboards in the Keyboard Room to the Pro Tools system in the control room. Sure, we had a wall plate in the Keyboard Room that connected to the control room, but it was proving to be a little troublesome with some noise. A DI box remedied that, but left me wondering. The wiring was pre-existing from the previous studio owner, and it made me a little nervous that we were getting such a nastly buzz when we connected a stereo keyboard that was also playing back locally in the room out of the Mac Mini that was running Synthogy Ivory II. I worried that there would be an issue in front of a client, and that is just not okay with me. I need to know that things are about as bullet proof as they can be.

So I thought about my options.

AVB To The Rescue

As I pondered this issue, I realized that the Mac Mini in the Keyboard Room was connected to a MOTU 24Ao, and the control room has all the patch bays connected to a MOTU 16A. Eureka! These 2 units should connect over the network, and allow routing of the 24Ao signals directly to the 16A via AVB.

Of course, this was still theoretical. I hadn’t actually figured out how to connect them via AVB. Nor did I have any previous experience with AVB, specifically. I have used audio over IP (AoIP) protocols before, such as Danté and Metric Halo’s proprietary MHLink, so I was confident this was achievable.

A Question of Networking

When I pulled up the MOTU discovery app on the control room Mac (connected to the 16A via Thunderbolt), I was able to see the 24Ao that was connected to the Mac Mini in the Keyboard Room.

“Okay,” I thought to myself, “that’s a good sign.” Since the 2 interfaces were connected to computers that could see each other over the network, they could both be detected from the control room Mac, but they were not yet able to pass audio between them. The AVB connection had not been established.

So I did a little digging around, and found that I was going to need to connect the interfaces to each other via the ethernet ports while they were also connected to their host computers via Thunderbolt (the 16A) or USB (the 24Ao). This would establish the AVB connection, and allow seamless routing between the two interfaces. Or so I hoped.

Headphones?

I pondered the connection needs, and realized that we had Cat5e running to the live room and iso booths for our headphone system. Each connection came into the control room on a discreet cable run, and allowed for patching directly into our headphone system. I could use the feed from the keyboard room, and patch that into the 16A instead of the headphone system.

It was going to mean that we would need to run a headphone feed from a different port to the Keyboard Room, but that wouldn’t be a problem. There are other close by ports for that. So, I felt this was a good solution, realizing that in the future I may need to run a second network just for AVB. When that time comes it would be one of those “good problems to have” scenarios. So, I wasn’t concerned. For the here and now it solved our problem, and didn’t hamper our usual operations.

So, I made the connections and…

(No) Communication Breakdown

It worked! I was able to open the MOTU Pro Audio Control screen, and see both devices communicating with each other.

This was good. But I have been digital long enough that the first question I asked myself was, “How are they going to clock to each other?”

That question was easily answered when I went to the “Devices” tab for each interface, where it asked me if I wanted to make one of the devices the clock master. “Yes, please,” I thought to myself, and clicked that option in the 16A’s Device pane.

And when checking the 24Ao, it showed the 16A as the clock source:

Deep Breath

I felt good about my success, but I was also aware that the hardest part of the process may be ahead of me. I have to admit, my experience with the control software for these MOTU units has been frustrating to date. The routing setup is convoluted, and, in many cases, counterintuitive.

My first sign that things were heading in the right direction was when I looked at the routing sources for the 16A, and saw that the 24Ao was aggregated in the box’s routing.

A decidedly good omen! Now for decisions. I needed to decide where to route the AVB inputs so that they show up in Pro Tools. That means I have to assign them to a “to computer” output source. So, I assigned them to outputs 9 and 10 (odd & even to be picked up in Pro Tools as stereo source), which looks like this in the routing pane:

Hearing Is Believing

With both units connected and communicating over AVB, and the routing set to allow for the 24Ao in the keyboard room to pass audio through the 16A in the control room to Pro Tools, I created a test session to see if this all actually works.

Success! I was able to get the audio from the keyboard room through the AVB network to Pro Tools in the control room. Of course, you may be asking, “What about MIDI?” Yes, I know. I thought about that too, but that will have to wait for another article. It’s an equally interesting solution.

I came away from this experience with the realization that a lot of the wiring in the studio could be replaced with a separate AVB network. It would be a very flexible setup. Moving past two interfaces would require the addition of an AVB capable router, which is a trivial requirement as any expansion would require a router anyway. That said, it looks like AoIP is here to stay, and AVB has proven to be a powerful option.

MOTU AVB Control Software

The MOTU interfaces use an excellent control app which rather than being an app you have to install on your devices, is a web app which is served by the hardware, brilliant for BYOD (bring your own device) environments. For example your clients could access their headphone mixes from their smartphones. See how it works in this walkthrough video.

What Is AVB Anyway?

AVB is different to some other AoIP systems like Dante and RAVENNA. In this 3 part primer series Julian Rodgers explains this standard.

More AVB Hardware