Question about Krell pre-pro HTS7.1

Set the computer's sample rate to 24/48 and see if you get audio

Can you see red light at the Tos jack when plugged into the Mac 

Yes, I can see the red light.  I will have to figure out how to check the sample rate.  Thank you,

I'm not an Apple guy but it is a sound card setting.  

try a cd player or dvd player first

Good suggestion on a CD player , it's 44.k by default 

Thank you for the responses.  My new idea now is to go from the iMac with optical into a converter to a standard jack configuration and utilize those outlets on the back of the pre-pro and bypass the optical connection.  Sound feasable?

Thank you for the responses.  My new idea now is to go from the iMac with the optical toslink outlet into a converter that converts the signal to a standard RCA configuration that fits  the processor.  Sound OK?