Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
Paul wrote:
> In article <lLChc.64477$I83.1318728@twister.tampabay.rr.com>,
> "JMartin" <me@privacy.net> wrote:
>
> > The mobo is:
> >
> > MIC2* *AGND
> > MICPWR* *+5VA
> > Line out_R* *BLINE_OUT_R
> > NC*
> > Line out_L* *BLINE_OUT_L
> >
> >
> > The plugs from the front of the case are:
> >
> > M BIAS
> > M IN
> > Speaker R (one wire, two plugs)
> > Speaker L (one wire, two plugs)
> > Ground
> >
> > This is how I connected the wires:
> >
> > MIC2 -> M IN
> > MICPWR -> M BIAS
> > Line out_R* *BLINE_OUT_R -> R Speaker (both plugs)
> > NC*
> > Line out_L* *BLINE_OUT_L -> L Speaker (both plugs)
> > AGND -> Ground
> >
> > Headphones work front and back. Audio works fine in the back but
> > poor in the front. That is, using Dragon NaturallySpeaking, the
> > volume check is good but fails on the sound quality part of the
> > test. It works fine plugging into the rear panel.
> >
> > Any thoughts?
>
> Your wiring looks OK, but I wonder if the case wiring is properly
> labelled or not ? There are certain computer cases out there,
> where there are wiring errors. M_IN should correspond to the
> Tip of the mic jack, while M_BIAS should correspond to the Ring
> contact. If you plug in a male-male 1/8" stereo cable, you should
> be able to measure +5V between the middle contact (Ring) and the
> contact closest to the cable (Sleeve-aka-GND), using a voltmeter.
> The +5V comes from the bias signal, which is a 2K resistor to the
> +5V supply on the motherboard.
>
> To get more information about what is going on, I would want
> to use a recording application that has a GUI that draws
> an analog waveform of what is being recorded. Then, plug the mic
> into first one jack, make a recording, and then repeat for the
> second jack. To make a controlled sound source, try to record
> the same source material from your stereo, holding the
> microphone the same distance from the speaker for both
> recordings. Then, compare the waveforms from the two recordings
> and see how they differ.
>
> If the only difference in the two recordings is the amplitude,
> that implies there is some difference in the gain path between
> the two microphone inputs. Changing the gain setting in the
> mixer control panel will fix that. Check to see whether the
> +20dB microphone boost check box has been selected or not.
>
> If the shape of the waveforms is different, then you'll have
> to guess at the cause, based on exactly how the two waveforms
> differ. For example, if the waveform is clipped (flat tops on
> sine waves for example), then something is limiting the signal.
> There could be some kind of noise mixed with the signal. For
> some of these, perhaps describing the difference between the
> two recordings, or posting the recordings on the web, so
> we can look at them, we might be able to give you some
> feedback on a possible cause.
>
> A web page on electret microphones claims that the MIC and
> MICBIAS signals are shorted together inside an electret
> microphone. If this information is in fact correct, then a
> wiring error won't account for the problem. If your microphone
> is dynamic, I would think reversing the wiring (MIC/MICBIAS)
> would give you no sound input from the microphone. So, chances
> are, something else is responsible for the difference between
> the two paths.
>
> Most likely, the Dragon application is complaining about the
> amplitude (and your gain setting). I doubt the application
> is clever enough to figure out anything else about the
> signals.
>
> HTH,
> Paul
Where can I find this gain setting? I'm using Windows XP.
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