Logic Pro/Express: Digital input not available

Logic Pro and Logic Express cannot access the digital input on certain computers. The affected systems will list the digital input as a separate device in Audio MIDI Setup. To check your system, follow these steps:

1. Open Audio MIDI Setup (located in /Applications/Utilities).
2. Click the Audio Devices tab.
3. Open the Default Input pop-up menu.

If your system shows more than one built-in input source, it will be affected by this issue.

Logic cannot access devices that offer only an input, and therefore cannot use the digital input. On systems with Mac OS X 10.4 or later, you can work around the issue by creating an aggregate device that uses the I/O from both available audio devices on your system.

To create an aggregate device in Audio MIDI Setup:

1. From the Audio menu, choose Open Aggregate Device Editor.
2. Click the plus (+) button to the left of "Add and remove aggregate devices on your computer."
3. In the bottom panel, select the checkbox in the Use column for each device.
4. Click Done.
   
   
5. In the Audio MIDI Setup, under Properties For: Built-in Audio, click Clock Source.
6. Select External

In Logic, you can now open the Audio Drivers window (Audio > Audio Drivers), click the Core Audio tab, and choose the new aggregate device.