Step 4: Select The Aggregate Device In Your Software Since my Mbox would be a more reliable clock source, I have selected it as the clock source and ticked the resample box for my built-in output. In my example below, I have selected my Mbox Mini and my built-in output. If the devices do not support word clock, tick the checkbox labelled “resample” for the respective devices except your clock source. If your devices support word clock, connect them together to provide sync. Once you have selected the devices you wish to use, you will need to choose a device which is the clock source or the master. Just check the checkbox that says “use” to add the device. Select the aggregate device and you will see all your available audio devices that you can use to form the aggregate device on the right. You should see a window similar to the one shown below. This is not the same as the audio preference pane under system preferences. This is the application used in Mac OS X to configure your audio and MIDI devices. You can find this under Applications - Ultilities - Audio MIDI Setup. This is exceptionally useful as most software only allows you to select one audio interface at a time. You can combine them to use them as a single 6-channel audio interface. If you have a 4-channel interface and a 2-channel interface. With this aggregate device, you can increase your audio inputs and outputs without purchasing another multichannel audio interface. If you have more than one audio device, you can use them as a single device known as an “aggregate device”. This concept works by creating an aggregate device.

I am sorry about this tutorial will only apply to Macs so Windows users are out of luck. This can be very useful if you have multiple audio interfaces and want to use them together for more simultaneous inputs and outputs. This is a true gem for Mac users especially when most DAWs do not allow you to use multiple audio interfaces.

Mac os 10.12 multiple audio outputs