Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
You are responding to a question that was posted 10 years ago.

iMacs from 2017 or later don't support optical audio output - although there's a page on Apple support that is a bit confusing because it talks about number of bits and bit rates (but that is actually talking about the digital-to-analogue converter inside the Mac).
It is a 2011 iMac
 
I have the same issue. If Isolve it I will post it!

threadnecro.png
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.