I have two DVD players connected to 990.
Oppo 981 and Sony DVP-CX955V. Using the same DVD with 5.1 in both cases. From Oppo the 990 immediately switches to DD when it sees it. From Sony it does not. Both are configure to DD 5.1 and I'm using the same disc for testing.

Both fed the 990 with coax. So I switched the coax in case of problem. Got same result. Tried optical and got same.

Talked tonight wth a friend who has 990 and Oppo 981
and same Sony. By phone tonight we confirmed both configured the same from sources. His Sony display on the machine and screen was same as mine, but his 990 accepted DD signal. And when I scroll thru the Dolby modes I get PROLOGIC IIx MOVIE AND MUSIC and also "DOLBY PROLOGIC II MOVIE + DOLBY VS 5-SP WIDE", which I don't think is DD 5.1.

So I've eliminated the variables I can identify. Seems like the 990 is not decoding it from the SONY 955 which is clearly feeding a DD 5.1 signal.

Any ideas???? and, yes, I upgraded the firmware.
Thanks

I'll ask what may be a silly question, but have you confirmed that the Sony's output is set to "bitstream" and not "PCM"? The behavior that you describe would suggest that the player is downmixing Dolby Digital to PCM, as would happen if PCM were selected instead of bitstream.

Thanks. That did it.
There was a part of the audio setup I had never seen. It was under "quick setup". I was using the other audio setup section which did not allow for this. It now does. Not only that but I was able to correctly set my dts. As always, thanks.