Successfully using Aggregate Devices in Pro Tools is at best a dark art and at worst a total car crash. In this free tutorial from Pro Tools Expert, Technical Editor James Ivey shows you to make the most of your 32 channel I/O count in a Pro Tools Native (non HD) system by using the Aggregate Devices feature of both Pro Tools and macOS.

If you are running Windows, don’t worry, James will explain how to do this in a subsequent article.

If you have more than one interface to hand, this technique to help you build a larger, stable Pro Tools system to enable you to record with a greater number of inputs without the need to scrap or sell your old gear and buy the next great, bigger and better interface.

Selecting & Setting Up The Hardware

I’m quite sure that many of you will have a “spare” or “old” audio interface hanging around in the bottom of a cupboard or on a shelf not being used. How often have you run out of microphone inputs on a session and wish you could just plug in that old interface and make use if it’s 2, 4 or 8 mic pres? What you may not be aware of is that you can, by creating and using a Pro Tools Aggregate Device.

In this article and video, we are going to show you how and also advise you on where the pain points are and how to sidestep them for a macOS setup.

Gear: For this example, we are using an Antelope Audio Discrete 4 Synergy Core and an RME Fireface UFX+, which both have 4 mic preamps. One of the other key features of these units is that they both have standard 75ohm Word Clock I/O. This is very important and while Aggregate Devices can work without Word Clock using the inbuilt CoreAudio Drift Correction system, we strongly recommend that is better to have hardware clocked at source at the hardware end rather than in software once it gets to the driver software and the DAW. You can use both but surely its better to be safe than sorry and all that.

Connections: Both the Antelope Discrete 4 and the RME UFX+ are both USB and Thunderbolt-equipped interfaces. So just to spice it up we are running the Discrete 4 under USB and the RME UFX+ under Thunderbolt. The only other data connections are the Word Clock out from the Discrete 4, which I have set to the be the clock master for this session into the word clock in of the UFX+ which is set to be the slave.

Configuring The Software

Once you have set up the hardware side of your Aggregate Devices, it’s time to configure the software. Most audio interfaces these days will have driver or control panel software. Make sure these are installed and up to date for all the interfaces in your Aggregate Devices rig. Then make sure that the Word Clock master and slave or slaves have been assigned correctly in the interface control panel. All interface manufacturers tend to do this differently but the rule is you can have as many slaves as you like but only ONE master. Word Clock flows out from the master into and through the slaves and the last slave device should either be terminated with a hardware 75ohm termination BNC plug or where devices have it use the button to switch on termination. Termination stops the clock signal bouncing back up the cable and messing with the clocking signal.

Audio MIDI Setup

It’s now to time to open your macOS Audio MIDI Setup application. If the Aggregate Device is NOT shown in the left-hand list you can create one using the + (plus) button in the bottom of the list. Once created you can choose which hardware devices form part of your Aggregate Device setup. Here we are choosing the Antelope Discrete 4 and the RME UFX+. The order in which you choose the devices is very important as it is the order in which the devices will be presented in Audio MIDI Setup and your DAW. As a rule, I choose the clock master device first then the interfaces with the smallest number of channels. In this case, we have 2 devices but well over 100 potential audio channels to deal with. You can remove or delete channels that you feel you are not going to need but this can make things tricky later on when you come to assign input and output channels in Pro Tools. Remember some devices like the RME, are reporting not only the channel number but also the type of I/O. So channels 9, 10, 11, and 12 are showing up as mic inputs. Not all interface manufacturers add this level of detail into their driver so thank you RME for your attention to detail.

Launching Pro Tools

Lastly, we launch Pro Tools, create a new session and make sure we have the new Aggregate Device assigned in Hardware setup. Now we can create our tracks and assign the Inputs and Outputs for our session following the listing provided in Audio MIDI Setup or by following the channel names in Pro Tools.

Check out the video below for the full setup guide.

The processes and principles outlined in the article and video are the same no matter which audio interfaces you are choosing to aggregate, and you can, of course, aggregate more than two. However, remember you are only ever going to be able to get 32 channels in and 32 channels out of a Pro Tools Native or Vanilla system. If you need more than 32 channels of I/O with Pro Tools you are going to need to invest in Pro Tools HD Native Thunderbolt or HDX Hardware systems to get the extra channel count.

What About Windows?

In the next article James will show you how to do the same on a PC running Windows 10.