Mac Computer "Core Audio" vs. "Default" or "System" Output

I am using two Macintosh computers as players connected to DACs. One is also the Core and Server the other is just an endpoint. On both computers in Roon “Device Setup,” I am offered the choice to use “Core Audio” or “System Default” audio.

What is the difference? Which do I want to use and why?

Core Audio will provide a lossless environment and give Roon exclusive control over the audio device. System Default will put Roon through the OS Audio mixer and then out whatever device has been selected as default. This is not exclusive and the mixer will downgrade the audio usually. Try them both and look at the signal path in Roon.


Thank you for the explanation.

So I tried the Core Audio on the iMac (which is running Core, Server, Control and Endpoint) and noticed no difference. Went back and clicked on the “exclusive” switch and that crashed the Mac’s audio device software such that I could not load the audio preferences window and could get no audio including that Roon would not play. A reboot was needed. Tried it again, crashed again, rebooted again. Won’t try a third time.

macOS High Sierra v 10.13.6

iMac 27-inch, Mid 2010
16 GB memory

The Laptop that’s running as a Roon endpoint does work correctly in Roon Core Audio Exclusive mode - OS v 10.13.6, mid-2010 MacBook Pro.

I have ordered a USB DAC for the desktop iMac hoping to run Roon through USB separately from the other Mac computer sounds running on the “default” but I am beginning to think that won’t work.