optical audio output not working on mac mini

I have a brand new mac mini (less than a week old) that I've hooked up to my media center. Unfortunately, when I hook the optical audio output to my Pioneer receiver, I get no sound. I know the receiver decodes optical audio correctly because it does so with my DVD player and my Xbox. I have tried all 4 optical inputs on the receiver, and have tried two different optical cables, as well as 2 different optical adaptors (required by mac mini to go from TOSLINK to the mini TOSLINK output on the mac). This tells me that all signs point to the problem being with the mac audio optical output stage itself. I have called apple technical support and have had it looked at, at an apple store. Unfortunately, the apple store does not carry a device where the audio output could be plugged in to verify that no sound is delivered. Apple refuses to replace the unit because I cannot prove to them that the problem is with the mac mini and not with the pioneer receiver. I find this incredible. My first experience (and quite possibly my last) with a mac has proven to be a nightmare.

Before I contemplate returning the unit and demanding my money back, is there any help anyone can provide....some magic bullet I've overlooked? Has anyone else had this problem?

Thanks....