How are your routing the input of your tv or cable box? Do you have a digital cable box? Not sure what kind of hook ups you have into the back of your receiver, but I use the optical output out of my digital cable box and run it directly into the back of my Denon receiver. I set the denon up to use the optical input, and then set the receiver to Dolby pro logic. When it gets a Dolby signal from the cable box, it handles it as a true 5.1. If it gets a non-5.1 signal it just matrixes the sound into 5.1. Re-Read your manual unfortunately they all kind of suck, but hopefully this will help make it clearer. Your setup for cable vs a dvd player is virtually the same. BTW, you may also need to adjust some settings on the cable box as well. Hope this helps.