I finally got my system up and running. (Thanks to many of you who help with your advice and ideas.) I am able to get digital 5.1 from my DVD, but not from my Comcast cable box. The info on the show I am watching indicates it is being broadcast in 5.1, but my receiver switches to surround 7.1 (Yamaha 5960). I have optical fibers going both from my DVD and the cable box to the receiver, using component cables for the video. Am I missing something here?
The Comcast STB (if it is made by Motorola) has an internal menu setting which controls the audio output.