Set aggregate device settings in Audio MIDI Setup on Mac
For your aggregate device to work correctly, you may need to set the sample rate and enable synchronization for one or more of its devices.
Set the sample rate
Ideally, all devices in an aggregate device use the same sample rate, matching the device chosen from the Sync Source pop-up menu. If your devices have different or fixed sample rates, you can still combine them: Choose one device as the primary sync source, set its sample rate, then enable synchronization for the other devices to convert their rates to match.
In the Audio MIDI Setup app
on your Mac, click the name of your aggregate device in the sidebar.
Click the Sync Source pop-up menu on the right, then choose the device you want to use as the primary sync source for the aggregate device.
In the Sample Rate pop-up menu, choose the sample rate for the device you selected.
To minimize resampling, set matching sample rates across devices.
If devices don’t support the same sample rates, choose the closest option and enable synchronization for each unmatching device.
Note: Even devices with the same sample rate may occasionally correct because of individual device clock timing drift.
Manage synchronization
If none of the devices in the aggregate device are synchronized using hardware, or if they use different sample rates, you need to enable synchronization (known as drift-correction or resampling). Synchronization compensates for drift in the data between devices and converts each device's sample rate to match the primary sync source.
In the Audio MIDI Setup app
Choose your aggregate device settings.
If all of the devices in the aggregate device aren’t synchronized through hardware, click the Sync Source pop-up menu, then choose the device with the most reliable clock. Select the Sync checkbox for each device.
If some of the devices in the aggregate device are synchronized through hardware, click the Sync Source pop-up menu, then choose the most reliable clock or your primary hardware-synchronized device. Select the Sync button for each device that isn’t synchronized through hardware.
If the sync checkbox is unavailable the synchronization can’t be modified for those devices.