Question about Krell pre-pro HTS7.1

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?

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?

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

try a cd player or dvd player first

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

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

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

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