cant get motherboard to output 5.1

KP84KP84
edited July 2007 in Internet & Media
I have a Asus a8n sli premium motherboard. But the problem is i can only output 5.1 sound using the 3 3.5mm cables to my speakers (logitech z5500) but when I connect it the speakers using a phono cable and SPDIF the pc only sends stereo sound am i doing somthing wrong?

Comments

  • stoopidstoopid Albany, NY New
    edited July 2007
    Some sound cards limit what is allowable with the digitial out. I have an Audigy 2 "Value" that refuses to send a 5.1 signal through spdif. Ironically, the 'lesser' SB Live I have sends the spdif 5.1 through coax just fine. Ended up downgrading the audio card in my home theater PC to get digital out to my receiver to work. I did some research and discovered that this was intentionally limited on the "Value" version of the Audigy 2, and the only way to get it to work was to perform a driver hack. Not being interested in spending any more time than I already had, I just kept the downgraded SB Live which is fine for my needs.

    If you list your audio chip manufacturer and model number we might be able to find out definitively if that's the case for you.
  • KP84KP84
    edited July 2007
    Thanks for the help.

    I did some research and found the problem. Basically to get dts or dolby sound from spdif the audio source needs to be in that format like ac3. So if you try using windvd which supports dts and dolby ect.. you will get 5.1 sound from spdif, if you would like all sound to be output in 5.1 you need some kind of dts encoder i cant seem to find any software ones but there are a few sound cards that do this in real time such as the auzentech ones which use the cmedia chips so the cmedia cards do this as well or the other option is to use this http://www.creative.com/products/product.asp?category=1&subcategory=16&product=14191 the hardware encoder. So i dont understand how you are getting 5.1 from optical unless you have a software encoder or your sound card does this.
  • stoopidstoopid Albany, NY New
    edited July 2007
    The SB Live does pass through, sends a raw bitstream and my home theater receiver automatically detects and decodes the bitstream. That's how it really should work.

    PCM is AC3, AC3 is PCM. Shouldn't matter what format the sources is in (AC3 DTS, DD5.1, etc) so long as the software just passes the raw data to the sound device which physically sends it to the decoding receiver. I listen to DTS, 5.1 AC3, Straight DD5.1, and high res audio (24bit/192) all through the same single digital coax connection. ONLY downfall is I can't use the software effects. The onboard processor on the SB Live can't encode its effects then decode it to a raw bitstream to send to the coax out in real time. It will encode then pass through the analog outs I believe. Funny thing is - the SB Live isn't even analog 5.1 capable, and yet I get digital 5.1 out of it. :p

    Good page to start on is:

    http://en.wikipedia.org/wiki/S/PDIF

    Then follow links from there. Enjoy the ride!
  • stoopidstoopid Albany, NY New
    edited July 2007
    BTW, there's a setting in the sound settings (windows and/or the drivers) that allows for "digital output only". This doesn't work for most gamers since many games can't/won't output through spdif, only analog.
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