K8N - no audio out rear port

Discussion in 'Asus' started by cranbrook, Jan 17, 2005.

  1. cranbrook

    cranbrook Guest

    I've just set up a K8N with winxp pro, and most items seem to do well.
    However I don't get any sound out of the rear line out port, the lime
    one. The case I'm using has front ports wired up for mic and output and
    they work fine. I had updated the nvidia chipset drivers to the latest
    but found that the multimedia controller (or something like that)
    failed, so for that one component I installed driver off of the CD that
    came with the mobo. I wouldn't expect that wiring up the case front
    speaker port would disable the rear speaker port, but could it be so?
    Are there any other suggestions?

    cranbrook, Jan 17, 2005
    1. Advertisements

  2. cranbrook

    KLH Guest

    Carefully recheck the wiring for the front panel. If it is not correct,
    the back panel audio will not work.
    KLH, Jan 17, 2005
    1. Advertisements

  3. cranbrook

    Paul Guest

    Before you wired up the front panel audio, there were two jumpers.
    These jumpers provide continuity from the front headset to the back
    lineout jack.

    If a computer case has five wires for the front headphone (ear_l, ear_r,
    return_l, return_r, gnd), then when the two jumpers are removed,
    contacts inside the computer case headphone jack take the place
    of the jumpers. Plugging in the headphones mutes the lineout on
    the back. Unplugging the headphones, causes the lineout to work
    again, as the contacts in the jack close, and ear_l connects
    to return_l etc. Thus, with headphones unplugged from the computer
    case, the headphone jack functions like the two jumpers were there.

    If, like many computer cases, there are only three wires (ear_l,
    ear_r, gnd), there are no return wires. To fit those three wires,
    obviously the two jumpers must be removed. But with no jumpers,
    there is no path ever, where the jumpers used to be. The bline
    pins are floating in space. You cannot get the mute function
    with a three wire front panel headset connection, but if you
    can find a way to "fake" the jumpers being present, while the
    three wires ear_l, ear_r, gnd are connected, then you will get
    sound from both the headphones and lineout at the same time.
    Such a short circuit could be arranged, by extracting a single
    strand of wire from some AC zip cord (lamp cord), and wrapping
    it around the pairs of two pins normally occupied by the jumpers.
    I.e. line_out_l to bline_out_l via a thin strand of wire and
    line_out_r to bline_out_r via a second thin strand of wire.
    Enough space must be left on the header pin, to then shove
    the ear_l and ear_r case wires, onto the line_out_l and
    line_out_r pins, respectively.

    If you cannot manage to fake the presence of jumpers, and
    you have a three wire front panel headphone connection, then
    all that will happen, is what you've already seen. No working
    lineout jack on the back. If you remove ear_l and ear_l, and
    put the jumpers back, then lineout on the rear will work again.

    Paul, Jan 17, 2005
  4. cranbrook

    cranbrook Guest

    Paul, that makes sense and I appreciate the time you took to write it
    up for me. I'll take things apart and see what I can do with the info
    you've provided.
    cranbrook, Jan 17, 2005
  5. cranbrook

    cranbrook Guest

    Wiring worked...thanks.

    I however have not been able to get the mic set up to work with either
    front or rear port. The case and front panel labels are pretty
    confusing, I think I have it wrong. Any clues?

    Five wire front port cables are labelled:
    gnd, gnd, L speaker, R speaker, mic

    K8N offers:
    mic2, agnd, micpwr, +5A, lineout R,BLineOutR, NC, lineout L, BLineOutL.
    cranbrook, Jan 18, 2005
  6. cranbrook

    Paul Guest

    OK. Your case has two grounds, and that _could_ be a problem.
    On a good case, the grounds are joined inside the case, and
    if that is the way your case is designed, then only one of the
    two ground wires would need to be connected.

    If the company that made your case was lazy, the grounds could
    be separate.

    In any case, start by connecting the "mic" wire to the MIC2
    pin on the Asus 2x5 header. Plug in a Walkman or other
    line level test source. Now, go into the mixer or audio
    control panel for the onboard sound, and find a hidden setting
    that selects between front and back microphone. It could be
    labelled something like MIC1/MIC2 or the like.

    The purpose of the Walkman or other kind of line level (1 volt
    AC) type test signal, is to find out if the wiring is complete
    or not. If, with MIC2 selected on the computer, and the Walkman
    plugged in, it could be that the second ground wire really needs
    to be connected.

    To find an extra ground pin, you can find GND pins on the
    USB headers. Have a look in the manual, for other motherboard
    headers with a ground connection. In the past, I've recommended
    using one of the two ground pins on the AUX 1x4 audio header,
    and that is fine, except that the pins might be too small to
    hold your case wire securely.

    Now, the next issue, will be the use of electret microphones.
    A 1/8" stereo type plug, has three contacts. This epanorama
    web page has a picture of the plug on an electret mic:

    http://www.epanorama.net/links/audiopro.html (main page)

    / \
    | | Audio signal == MIC2
    \ /
    | | Bias voltage for microphone (+5V through 2.2 kohm resistor)
    |===| == MICPWR
    | |
    | | Ground == AGND
    | |
    | |

    Your computer case has no way to get MICPWR to the second
    contact on the jack. Which means an electret microphone won't
    work, with just MIC2 and AGND connected normally. But other
    kinds of mono sources might work, like the Walkman used for
    this test. (For passive microphones, you'll need to enable
    the 20dB microphone boost button, but in some cases, even that
    is not enough. An electret is much better for the average
    recording application with the MIC input. A passive microphone
    equipped with a preamp will also work. Of course, the mic input
    on the back of the computer will have MICPWR on its second

    You could either look at some of the powering options
    noted on the microphone_powering web page, or find a better
    drive bay mounted set of jacks. The Asus J-Panel drive bay
    mounted product, has ear and microphone jacks, and they
    mate exactly with an FPAUDIO header. The J-Panel also
    has SPDIF and USB connectors. The first one I could find for
    sale via a search engine, is here:


    Paul, Jan 18, 2005
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.