Sony DVP7700 not producing DTS output.

Hi All!

I have a Sony DVP 7700 player that is connected to a Denon AVR 5700 receiver using a BetterCables digital coax cable. Now, when I play a DVD with a Dolby Digital (DD) track only, the player detects and feeds the DD signal to the receiver which puts itself in DD mode; however, when I play a DVD with both DD and DTS tracks, the Sony doesn't seem to detect the DTS signal, and consequently falls back to DD. For example, playing Jurasic Park 3 yields DD only. I have configured the Sony to enable DTS output, but without success -- the player's DTS LED indicator never lights up and the receiver's input mode never budges from DD. I've battled long and hard and obviously still missed something. Can anyone set me straight on this one? Thanks so much.

Regards,
Robert Gairns.