Digital in as a interface

Umm, OK, that should work -- you'll need a program of some description to capture the incoming (digital) audio to a file on disk. GarageBand, SpinDoctor, Final Vinyl, Audacity or some such.

Unless your CD is broken in the Mac, though, what is your anticipated benefit of doing this - vs. copying or ripping directly from the CD?

I thought of one reason - if you have Mini-CDs or business card CDs and a Mac with a slot-loading drive.

 

I cannot see why you would want to do this. It would sound worse doing it this way than using your Mac CD/DVD ROM drive. Just an example, your CD player does not output a clock, so you'll get jitter errors. There are many more factors but I wont go into detail.

 

If you insert a red book CDA into your Mac Mini, the CD volume will mount, and the music files in the volume will show as AIFF files. Just copy paste them to your HDD.

 

if he's recording digital out to digital in, it's probably s/pdif format, which does indeed carry clock information.