If you experience a situation where you are unable to change the surround setting, you will need to have a signal present when attempting to make the mode change. This effects digital inputs only.

Ah-ha. That explains Kwok and pills' problem - source (DVD player in both cases) is set to a digital input, input is inactive (presumably device is off, or in Kwok's case has an SACD disc in it that does not offer a digital output), and so the 990 won't let the user manipulate the surround mode. Glad to get that puzzle sorted out...

Thank you guys. Happy writing and reading.

Regards.

Kwok

Thanks guys,problem solved.

I have another discovery. DTS 5.1 can only be changed to DTS Neo6 by the DTS Mode button on the main remode, when playing DTS 5.1 movie. I have to go to MAIN manual to change to DTS+ PLIIx Movie if required. Anybody encountered the same ?

The DTS button only offers options for DTS processing modes - which with a DTS 5.1 source means straight DTS and DTS+NEO6. Applying Pro Logic IIx to a DTS source is considered Dolby processing, and as such is only available by pressing the "Dolby Mode" button on the remote. (Interesting side note: unlike with older processors, the 990 will not let you apply DTS ES to DTS sources. This is because DTS issued instructions to manufacturers to only use NEO6 to generate surround back data from DTS 5.1 sources, since the processing used by DTS+NEO6 is exactly the same as the processing used by DTS ES Matrix with a DTS 5.1 source.)

Gonk: You are the best. The side note you pointed out is very interesting and I wonder how many people knew about it.
One thing that bother me about DTS Neo:6 Movie/music is for creating 6.1 channel sound from Stereo Movie or sound tracks. I wonder if the 990 picked up the stereo track from the movie instead of the DTS 5.1 track!?

Just a thought.

Kwok

NEO:6 serves two purposes - generating six-channel surround from stereo sources, and generating surround back data for DTS 5.1 sources (the role that folks previously equated with DTS ES's "Matrix" mode since it was a logical parallel to Dolby EX's ability to generate a surround back signal from regular DD 5.1 sources). I bet that you had the right track picked on the DVD player.

Gonk: If that is the case, should we stick to DTS NEO:6 instead of DTS+PLIIx? It seems to me we should use DTS NEO:6 on DTS Straight. What do you think?

Kwok

I think both are reasonable choices, and the best way to decide is to compare the two a few times and see if you have a personal preference. Why do I suggest this in spite of the fact that using NEO:6 would keep us solely in a DTS-licensed decoding environment? There are two things that cause me to leave the door open. First, both are being applied after the DTS decoding, so they are acting solely upon the left and right surround channels to generate the surround back information, so mixing DTS and Dolby by using PLIIx isn't quite as unappealing at it might initially seem. Second, PLIIx has an advantage over NEO:6 when it comes to generating a surround back signal, and that is that PLIIx generates discrete left and right surround back channels rather than the mono surround back produced by NEO:6 (and by Dolby EX, and many other similar matrix processing systems).