This has nothing to do with Yamaha. The 3.5mm line in jack on the Mac is also an optical input. You can not get an optical to 3.5mm adapter. You can get a fiber cable that is Toslink (a connector) to the special dual use fiber jack the Mac uses. The connection is only 2 channel so it can accept SPDIF. The connections on the MY16-AT card are not SPDIF they are ADAT, an 8 channel format. You would need an interface to take ADAT into your Mac in order for this to function. RME makes some nice ones that I have used for recording, there are quite a few others as well, I just don't have experience with them. The interface that you need would depend on which MAC you have and what it has for ports (Firewire800, USB 3.0, Thunderbolt).
You could also change the ADAT card out for a DANTE card as you and others had mentioned.
Lee
Lee,
Thank you for the information. It's been quite helpful reading around and learning a bit more.
What sort of interface have you record with? My Macbook has 2 Firewire ports (400 & 800) and a USB port, so I know that opens up my possibilities a bit more. I'm hesitant on the Dante card, just because of how expensive they are for the situation I'm in. I can't seem to find any used, so that sucks.
Thanks again for all the replies, I'm no expert on this subject, and I'm learning with each ridiculous statement I make. hah!