Discussion in 'Asus' started by Steve Fisher, May 19, 2004.

  1. Steve Fisher

    Steve Fisher Guest

    I've been lokking at possible accessiories for my motherboard A7N8x-E

    On the following website it is possible to get a module described as

    S/PDIF In-Out Coaxial Module.


    My question is what extra functionality does this give over the SP/DIF
    Out jack on the back of my motherboard.

    Thanks in advance for any hep


    Steve Fisher, May 19, 2004
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  2. Steve Fisher

    Paul Guest

    There is an unresolved issue with SPDIF-in and ALC650. I haven't
    seen anyone post about it in a while, but a while back, people
    couldn't get SPDIF-in to work. One poster was going through tech
    support, to see if Asus could resolve it.

    The problem with the way SPDIF is done by Asus, is there are a
    few components on an Asus adapter. The way the adapter is set up
    may not be appropriate for every SPDIF motherboard interface.
    And, Asus is probably not going to spin yet another version of
    the adapter.

    So, unless you can find evidence to the contrary, save your money
    for the time being. SPDIF-out is probably all that is going to
    work for you.

    It is hard to tell from the ALC650 documentation, whether the
    intent was for the chip to accept a sub 1 volt amplitude signal
    (AC coupled) and amplify it, or the signal was supposed to be
    a full 3.3V CMOS logic swing. From a chip design perspective,
    the latter is easier to do. Either the Asus adapter doesn't
    DC bias the ALC650 properly, or there is simply a mismatch
    of design intent - the SPDIF signal on the cable might be
    too small, if the ALC650 is looking for a full 3.3V signal.
    Since the ALC650 has a typical Taiwanese datasheet, we'll
    never know for sure.

    An adapter with a TOSlink receiver module might stand a
    better chance of working, as the output of the TOSlink
    is a logic swing signal, and won't need amplification.
    Good luck finding the Asus adapter that does that.
    See the SPDIF-all depicted below:


    Paul, May 19, 2004
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  3. Steve Fisher

    Steve Fisher Guest

    Is the jack used for S/PDIF out on the motherboard
    the same as that is used on the module S/PDIF In-Out Coaxial Module?

    Funnily enough it was the TOSlink out that i originally wanted but the
    only place that sells these ASUS modules in UK is ASUS UK. I sent them
    a cheque for £5 a month ago and when i chased up yesterday i found out
    that i was not down for a module which has TOSLINK.

    In fact I was informed that the modules with TOSLINK connections were
    not compatible with A7n8x-e!!

    Steve Fisher, May 19, 2004
  4. Steve Fisher

    Paul Guest

    Logically, the jack on the back is the same as a SPDIF In-Out COA,
    but physically they should be coming from separate line drivers, as
    the environment is supposed to be a 75ohm transmission line. Leaving
    a stub on the motherboard isn't a good idea.

    With regard to the adapter, did Asus claim that the Coax In/Out
    module would work ? Or just that the TOSLink wouldn't work ?
    Maybe in fact, it is the ALC650 SPDIF input that doesn't work ?

    I just took a closer look at the picture of the SPDIF In-Out COA
    on the mb_accessories link you posted, and I see a design change
    on it. There is now a 14 pin chip on the adapter! Maybe that
    means they have fixed the problem by buffering the input ?
    (Compare the picture of the module on the web.archive.org
    page I quoted, to the web page you quoted.)

    To continue this charade, put your fiver down on the COA, and
    post back how it works out :) Make sure Asus knows which mobo
    you've got, so they don't ship an older model of bracket, without
    that chip. ( Watching people gamble, is almost as much fun as
    gambling yourself :) )

    Other than that, maybe you could pick up an 8738 based PCI sound
    card, like the Chaintech one I see for $18 on newegg.com. It claims
    to have SPDIF In-Out coaxial.

    Paul, May 19, 2004
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