Aggregating Audio Interfaces with Mac and Windows

Yes, you really can use multiple audio interfaces simultaneously with a single computer

by Craig Anderton

You have a go-to interface that’s great, but then one day you run out of mic inputs. Too bad your computer can’t address more than one interface at a time . . .

Or can it? Actually, both Macintosh and Windows computer can let you use more than one interface at a time, if you know the rules.

For Windows, although with rare exceptions you can’t aggregate ASIO devices, you can aggregate interfaces that work with WDM/KS, WASAPI, or WaveRT drivers. Just select one of these drivers in your host software, and all the I/O will appear as available inputs and outputs in your application (Fig. 1).

Fig. 1: Sonar X1 is set to WDM/KS, so all the I/O from a Roland Octa-Capture and DigiTech’s iPB-10 effects processor become available.

With the Mac, you can aggregate Core Audio interfaces. Open Audio MIDI Setup (located in Applications/Utilities), and choose Show Audio Window. Click the little + sign in the lower left corner; an Aggregate Device box appears. Double-click it to change its name ("Apollo+MBobMini" in Fig. 2). You'll see a list of available I/O. Check the interfaces you want to aggregate, then check "Resample" for the secondary interface or interfaces (Fig. 2); this tells the computer to treat your primary, or unchecked, interface as the clock source. Now all input and output options will be available in your host program.

Fig. 2: Universal Audio's Apollo is being supplemented by an Avid Mbox Mini.

If you encounter any problems, just go to the Audio MIDI Setup program’s Help, and search on Aggregation. Choose Combining Audio Devices, and follow the directions.

Craig Anderton is Executive Editor of Electronic Musician magazine. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.