How to combine multiple audio interfaces by creating an aggregate device

By creating an aggregate device, you can use more than one audio interface at the same time with audio applications like Logic, MainStage, or most other Core Audio-compliant applications.

Logic and MainStage allow you to use a separate device for input and output, such as using a USB microphone and the built-in output of your computer. Use an aggregate device to combine multiple inputs and outputs for applications not manufactured by Apple which do not support separate input and output devices, or to combine multiple devices of the same model.

Set up an Aggregate Device

  1. From the Finder, choose Utilities from the Go menu. Open the AudioMIDI Setup application.
  2. Click the Add (+) button on the bottom-left corner in the Audio Devices window and chose Create Aggregate Device:

  3. A new aggregate device appears in the list on the left side of the window. To rename the device, double-click it:

  4. With the new aggregate device selected, enable the checkbox labeled "Use" on the left side of the Audio Devices window. Do this for each device you want to include in the aggregate device. The order in which you check the boxes determines the order of the inputs and outputs in applications like Logic and MainStage. For example, the first box you checked will be inputs one and two, the second box checked will be three and four, and so on.

    Note: The list on the right shows the currently connected audio devices and the number of input and output channels for each one.

  5. To use the clock of a device as the master clock for all the combined devices, choose the device from the aggregate device’s Clock Source pop-up menu. Choose the device with the most reliable clock:

  6. If your audio devices all work with word clock, connect them together using a word clock cable. Connect the cable from the device you designated as Clock Source in step 5 to the input of each other device. Refer to your audio device product documentation for specific details.
  7. If any of your devices do not work with word clock, enable the Drift Correction checkbox for the devices that are not designated clock master.

Using your aggregate device with Apple professional audio software

This section discusses how to use an aggregate device with Logic or MainStage. Your aggregate device may also work with Core Audio-compliant applications from manufacturers other than Apple.

To use an aggregate device with Logic:

  1. Open Logic Pro or Logic Express.
  2. Choose Logic Pro > Preferences > Audio or Logic Express > Preferences > Audio and select the Devices tab.
  3. Select the Output Device drop-down menu and choose the aggregate device from the list. The Input device will be set automatically; change it if you want to use a different device for input.

  4. Click Apply Changes at the bottom-right of the window.

To use an aggregate device with MainStage:

  1. Open MainStage.
  2. Choose MainStage > Preferences and select the Audio pane.
  3. Select the Audio Output or Audio Input drop-down menus and choose the aggregate device from the lists:

  4. Close the Preferences window.

    Note: MainStage can use the device defined in the Audio MIDI Setup for sound output or input by choosing System Setting for the Audio Output or Automatic for Audio Input.

To set the System Setting in Audio Midi Setup:

  1. From the Finder, choose Utilities from the Go menu. Open the AudioMIDI Setup application.
  2. Control-click or right-click on the device you want to use and choose "Use this device for sound output" or "Use this device for sound input":

  3. Close the Audio Midi Setup.

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