Perhaps I can help you with this problem but first i would have a few questions and would like to say that if you seem to lose me in the conversation then just refresh this window or manually scroll down to the last line , it does not auto scroll down to the last reply.
That being said;
When you say that you connected your denon by "phono " cables , do you also mean RCA type left/right plugs , usually one red and one white ?
If so , did you connect it at the back of the tv where it says " R audio L " next the the Y - Pb - Pr terminals ?
If so then those are inputs and will not do .
On your tv there are only 2 types of audio outs , one is the optical and if your denon does not have that type of input then the only one left will be the headphones jack that uses a 3.5 mm stereo plug .
That could be used with a cable that would look like the one at the link below ;
Other than that the denon could be connected directly into the cable box if you have one .