
For each device that is not the clock source, select Drift Correction.To set the clock source for the Aggregate Device, choose the device from the Clock Source menu. Choose the device with the most reliable clock.Drag a device to the left for lower input or output numbers, or drag to the right for higher numbers. To reorder devices after you've selected them, drag a device under Subdevices left or right.

Learn more about how to identify Aggregate Device inputs and outputs

Click the Add (+) button at the bottom of the sidebar of the Audio Devices window, then chose Create Aggregate Device.From the Finder, choose Go > Utilities, then open the Audio MIDI Setup application.When you create an Aggregate Device, make sure all external audio interfaces are connected to your Mac.
