5.1 conversion from stereo source?

[SJTrance]

I have an HD DVR from Time Warner here in NYC. I have a Pioneer VSX-90TXV hooked up to it using a 5.1 speaker setup (hooked up via an optical cable). When I use the "auto surround" feature, it checks what the source is and picks the appropriate type of digital decoding for the sound. Whenever I have it on any of the HD channels, it goes to the Dolby Digital setting. Whenever I am on any non-HD channel, it says, "Stereo" and only the front three speakers are active.

My questions are this:

1. Is it safe to assume that with most non-HD source with cable TV, stereo is the source found?

2. If so, and I wanted to use the rear speakers, what other decoding (correct terminology?) should I use? I can choose the different several options including pro logic, pro logic II, pro logic plus THX, and some other options like TV surround, extended stereo, etc.

Thanks for the help. I apologize for the newb question. I did try a search, but the question seems vague and I can't find a proper answer.

 

[MDS]

1. Is it safe to assume that with most non-HD source with cable TV, stereo is the source found?

With Time Warner in Austin, the channels are a mix of analog stereo, 48 kHz PCM stereo, DD 2.0, and DD 5.1.

2. If so, and I wanted to use the rear speakers, what other decoding (correct terminology?) should I use? I can choose the different several options including pro logic, pro logic II, pro logic plus THX, and some other options like TV surround, extended stereo, etc.

You'll have to experiment to see what you like. I use PLII Music mode almost exclusively because it has some adjustable parameters. Most receivers will remember what was last selected. So if you are receiving DD 2.0 and select the PLII decoder, when the source is again DD 2.0, it will remember and automatically switch to PLII - even if you change the channel and are getting DD 5.1 and it automatically switches to the Dolby Digital decoder.

Some higher end receivers also have menu settings where you can specify the default decoder you'd like to use. So you can have separate settings that say use PLII for DD 2.0 and Neo:6 for 2 channel PCM, etc.

 

[SJTrance]

Thanks for the reply. I can set it so that when the TV finds Dolby Digital channels, it automatically goes to that, but when I get stereo channels, it changes to the Dolby or THX settings. I will try out PL II Music. What do you mean by adjustable parameters?

 

[MDS]

PLII Music mode allows you to set Center Width, Dimension, and Panorama parameters. Neo:6 also has a Center Width adjustment.

Center Width allows you to spread some of the center signal to the front mains for a wider soundstage. Dimension moves the soundfield forward or backwards which is useful if the center is slightly forward or behind the mains. Panorama sends some of the front channel signal to the surrounds for a wrap around effect. Most of the other matrix decoders have no adjustments.