Front panel audio ASUS A8N-E

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Upgrading daughters computer and having difficulty getting front panel
audio for onboard AC97 sound to work.

Motherboard pinout is a follows:

     BLINE_OUT_L_-o    o-Line out_L
     BLINE_OUT_R_-o    o-Line out_R
         +5VA            -o    o-MICPWR
         ASNG           -o    o-MIC2

Available connectors are (on two separated lines)
     1. L-out
     2. R-out
     3. RET-L

     1. Ground
     2. MICPWR
     3. RET-R
     4. MICIN

Does RET_L/R to the coinciding BLINE pins, MICPWR to MICPWR, Ground to
ASNG, MICIN to +5VA and L/R-out to coinciding Line out pins sound



Re: Front panel audio ASUS A8N-E

Fitz wrote:
Quoted text here. Click to load it

Case      Motherboard
----      -----------

L-out  to Line_out_L
R-out  to Line_out_R
Ground to AGND

Do not connect anything to +5VA.

Connecting L-out, R-out, and Ground, should be giving you
stereo sound on the computer case front panel. Once you
connect RET-L and RET-R, that also allows the green Lineout
on the back of the computer to continue working, like when
no headphone is plugged into the front of the computer case.

If you remove the computer case wiring from the FP_AUDIO header
in the future, don't forget to put the two jumper caps back
where you found them.


Re: Front panel audio ASUS A8N-E

Thanks! The +5VA one was my only real concern. Thanks for the reply...


Re: Front panel audio ASUS A8N-E

I have an A8N-SLI Premium.  The front audio connector has 2 jumpers on
it.  The connector from my front audio panel has a AC'97 connector.
To plug it in I would have to remove the jumpers.  Is this OK?  The
front audio connector has a green headphone jack and a red mike jack.
 This is a cooler master case with a useless manual.  Thanks for your

Re: Front panel audio ASUS A8N-E

nantucketbob wrote:
Quoted text here. Click to load it

Yes, you remove the jumpers before plugging in a front panel
wiring assembly.

In terms of results, there are several possibibilities.

1) Some cases have "ordinary" stereo jacks. There are no
   "return" signals, to connect where the jumper plugs
   used to be. Without the "return" signals, you will lose
   the signal on the green connector on the back of the
   computer. The case would have wires like "Left", "Right",
   "GND", and is missing the return signals.

2) If the computer case jack for the headphone, has two
   side contacts, then the headphone jack supports "muting"
   for the green connector on the back of the computer.
   The signals would be "Left", "Right", "Left_Return",
   "Right_Return", and "GND". When headphones are plugged into
   the front of the computer, the Left_Return and Right_Return
   are open-circuited (thus muting any speakers connected to
   the back of the computer). The Left_Return and Right_Return
   signals are what feeds the green connector on the back
   of the computer, when the jumper plugs are removed.

   In this case, there are a couple metal contacts inside
   the headphone jack, that are pushed aside when the headphones
   are plugged in.

   This drawing shows what a jack with side contacts looks like.
   This jack would support muting of your rear green speaker

   The four signals in this case, connect to the four pins
   occupied by the jumpers. The jumpers take the place of
   the side contacts, when no computer case front panel
   wiring is being used.

3) Some computer cases "fake" the return signals. All that
   they do, is connect "Left" to "Left_Return", and effectively
   it is like they are applying the jumper plug to the
   header, when the wiring is installed. Such a computer
   case does not support muting, so the rear speakers
   work all the time, whether the headphones are plugged
   in or not. The headphone jack on the case does not have side
   contacts in this case, saving the case manufacturer a few

Now, let's review the symptoms to be expected.

1) Three wire cable for headphone.

   Result - rear speakers don't work. User must find a
   means to jumper the signals, where the jumper plugs
   used to be, to get the rear speakers to work again.

   Most practical solution - don't bother connecting the
   cheesy computer case front panel wiring to your
   motherboard. Put the jumpers back, and continue to
   enjoy a working rear green speaker jack.

2a) Five wire cable for headphone.

    A real headphone jack with side contacts could be
    used. Such a jack allows muting the rear speakers,
    when headphone are plugged in.

    If the user desires the rear speakers to be enabled
    all the time, then the user must find a means to put
    the equivalent of the jumper plugs back in place
    (i.e. short signal to signal_return, for left and
    right channel).

2b) Five wire cable for headphone, where computer case
    just shorts Left to Left_Return, and shorts Right
    to Right_Return. The "fake" five wire type.

    Speakers work all the time, when plugged to the back
    of the computer. When headphones are plugged in,
    the speakers won't be muted.

There are other cases to consider. For example, a motherboard
that supports "Azalia" or "HDaudio", the new audio standard,
has electronic connections for headphone and rear speakers.
No jumpers are needed on the FP_AUDIO header.
There are various sensing schemes, so the computer knows
when something is plugged in. It is a software matter,
as to whether the rear speakers are muted when headphones
are plugged in. In the older, AC'97 standard, the choice
was fixed by hardware, and the use of a couple of side
contacts (switches) in the headphone jack, to provide
a muting function. So HDaudio raises the possibility of
modifying the function of the jacks, via a Control Panel
in Windows. But as to whether the driver supports what the
user wants to do, is up to the whims of the chip maker and
their driver writers. In this case, the hardware has what
is referred to as a "cloning" function, where the signal
on the rear green connector, can be copied and sent to
the headphone jack, via the FP_AUDIO header.

If you want further clarification, provide a URL to the
Coolermaster installation manual, or at least provide
a list of the wires Coolermaster has provided.

If the Coolermaster has two GND wires, don't panic. The
FP_AUDIO header has one GND connection, and you can try
connecting just one GND wire and see if both microphone
and headphones are working. You can take a multimeter,
set it to ohms, and see if the two GND wires read zero
ohms between them. If you get a zero ohm reading, then
the GNDs are connected together on the circuit board
that holds the jacks, and then only one of the GND wires
needs to be connected. The other GND can be left dangling.

I have heard of cases where the two GND wires are not
connected together in a computer case, which is a PITA.
You then need to find another GND pin somewhere on the
motherboard, to ground the second jack. Or find a way
to connect two GND wires to one FP_AUDIO header GND


Re: Front panel audio ASUS A8N-E

I scanned two pages, one from each manual, showing pin-outs.  I cannot
figure out how to send the small jpegs to the forum.  I cannot find
the help page.  Your reply is WONDERFUL!  Thanks!   I want to be sure
I know what each of the pins on the diagrams do.  How do I send the

Re: Front panel audio ASUS A8N-E

nantucketbob wrote:
Quoted text here. Click to load it

Well, I'm responding to you from a USENET News server and not from a
forum. There are public (free) USENET servers, such as
that allow limited numbers of direct posts per day to USENET. (The pay
for use USENET servers are generally for people who download movies
all day long :-)) I'm currently using Thunderbird as a News reader,
and Thunderbird can be dowloaded from .
Thunderbird is an email and News reader all in one, and I'm just
using the News reader function, set to server.

There are image hosting sites, and they have limits as to how many
files they will host for you, how many times you can change the images,
and how much download bandwidth they will allow your viewers to use up.
Still, this is better than having to run your own web server.

Some forums allow HTML postings, and you can embed references to
an image hosting site in your message. Usually a forum will have
instructions on it somewhere, as to how to do some of those things.

When I need to refer to something, I try to find existing images
already stored on the Internet. I search for images or manuals
by using: /


Re: Front panel audio ASUS A8N-E

Paul.  I don't understand that insert image command.  Here are two
images on flickr. /

See if you can access those two photos.  The Centurion images is from
the Cooler Master "manual."  The A8N image is from the MoBo
manual.  THanks.   Bob Hall

Re: Front panel audio ASUS A8N-E

nantucketbob wrote:
Quoted text here. Click to load it

OK. Got the pictures.

Your computer case is type (3). When you wire it to the motherboard,
the headphone jack on the front of the computer case, and the
speakers wired to the green jack on the back of the computer, will
both operate at the same time. (I.e. No mute function.)
Some people like that, and some don't.

Here is how to do the wiring. (Note - make no connection to
+5VA, as it is a raw power signal. +5VA is intended for powering
analog amplifiers, and I haven't seen a modern case with an
amplifier in it. So you don't need to touch +5VA. All other
signals are relatively safe to use.)

L-RET --->  BLINE_OUT_L X   X Line_Out_L ---> L-OUT
R-RET --->  BLINE_OUT_R X   X Line_Out_R ---> R-OUT
                    +5VA X   X MICPWR     ---> MIC-POWER
GROUND <--->       AGND X   X MIC2       <--- MIC-IN

The arrows are meant to show the direction of signal flow, and
are not important to your wiring job. The signal comes out of
the motherboard, on the Line_out wires, and returns into the
motherboard on the BLINE wires. MICPWR is a small (2 milliamps)
flow of current for running electret microphones - it generally
won't hurt other cheap microphones. It shouldn't take you
long to hook this up.

To test the microphone, don't forget to find the setting
in the Mixer, that selects between microphones. On some
motherboards, you have to switch between "Mic1" and "Mic2",
to be able to use the front microphone. Depending on the
microphone type, you may also need to click the "mic boost"
button, which gives an extra 20dB boost to weak microphone
signals. You only need the boost, if you are having trouble
getting a signal from the microphone. So testing the microphone
jack, can be a bit trickier than testing the headphone jack.


Re: Front panel audio ASUS A8N-E

Paul, Thanks!  I decided to hook the AC'97 plug to the motherboard and
it works just as you said, no muting of the external speakers.
Perhaps you could explain the other two connectors: HD Audio and the
Azalia plugs.  I suppose there is no easy way to get muting.  It is
not important to me, but it might be to someone else.  Bob

Re: Front panel audio ASUS A8N-E

nantucketbob wrote:
Quoted text here. Click to load it

HDaudio and Azalia are two different names for the same thing. Azalia
is the original name, and HDaudio soon followed as a more "marketable"

First of all, as far as I know, no computer cases have HDaudio wiring.
They all seem to still be using AC'97 wiring. At least I have yet to
run into documentation on the web describing wiring suitable for
HDaudio. This means certain motherboards have dual personality
(HDaudio/AC'97) FP_AUDIO headers, but the computer cases still
seem to be AC'97.

HDaudio differs from AC'97, in that one of the design objectives was
to make the function of the audio jacks, more under software control.
They wanted the user to be able to plug a microphone into any
audio "hole" on the computer, the computer puts up a dialog box that
says "I think you just plugged in a microphone", and the user then clicks
"Yes" and the HDaudio chip is configured to digitize the microphone
input signal. To do this for any jack, in any way possible, would
require a "crosspoint switch" inside the audio chip, that can route
any audio jack, to any facility inside the chip.

Now, I don't know if this arbitrary functionality is completely implemented
in each HDaudio chip. For example, some chips claim you can "clone" a stereo
line_out signal, to a couple of other jacks. So you could listen to
a stereo signal with your speakers, and plug in headphones at the same
time. Whether the speakers are muted or not, would be under software
control. Perhaps the Mixer control panel would offer some options,
or some popup dialog box would ask you.

The FP_AUDIO header for AC'97 has a crude scheme for muting the rear
speakers. By means of four of the pins on the header, you can interrupt
the signal flow of the stereo Lineout connector. If the computer case
front audio wiring has the little switches inside the headphone jack,
when you plug in headphones, that stops the signal flow to the rear speakers.

(Example of a jack suitable for muting the rear speakers in AC'97 apps.
Pins 2,3,4,5 go to the FP_AUDIO Line and Bline pins. The two little
switches open when the headphones are plugged in.)

On HDaudio, there are a couple of schemes to implement the same thing.
The FP_AUDIO header (one equipped for either HDaudio or AC'97) has
wiring for two generic front panel jacks. Both will have provision for
electret microphone bias, provided inside the HDaudio chip. There are a
couple "sense" pins and a "return" pin on the FP_AUDIO header for HDaudio,
and an "HDaudio" jack on a computer case, would need a standalone switch
(i.e. the switch part is not wired to the audio signals at all) to signal
whether a jack was plugged in or not. (I am not able to find a suitable
jack on the Digikey site, which might explain why computer cases don't
have HDaudio type jacks.)

By means of the "sense" and "return" pins, it is possible for an HDaudio
chip to sense whether a plug has been inserted into any one of eight

The HDaudio chip also has a built-in impedance sensing function. The
chip can measure the impedance of the load. (This capability existed
on some AC'97 chips as well, so the idea was not invented just for
HDaudio). This is how the software can pop up a dialog box, asking
you to verify if you just plugged in headphones. A headphone has a
32 ohm impedance. Speakers might be 4 ohms or 8 ohms. The input on
your stereo might measure 10000 ohms (a very light load). The impedance
sensing function is not correct in every case, and it cannot distinguish
between all possible audio devices, which is why a dialog box asking
for confirmation, is put on your computer screen.

So, Hdaudio has:

1) More flexible (retaskable) I/O jacks
2) Ability to "clone" the same output signal to more than one jack
3) Ability to sense jack insertion, via a switch within the body of
    the audio jack.
4) Independent of (3), HDaudio can also measure the impedance of the
    load. (Some chips do it better than others.)
5) I think HDaudio also allows more bits of digital data per channel,
    and I think one direction of the digital interface might be
    running twice as fast as AC'97.

The above is all from memory. You can get the HDaudio standard from
the Intel site for more info, but this may not explain a lot to you.
(It didn't help me that much.)

This one is for wiring. Formfactors is an Intel sponsored site,
which also contains docs on design for computer components.

And for some tutorial material, there are links on this page:


Re: Front panel audio ASUS A8N-E

Paul: Great stuff.  I hope others read this!   The case I bougt
(Cooler Master) has an HD audio plug on the cable that comes from the
front audio connectors.  The one cable has an AC'97, and HD audio, and
those 10 or so individual (unlabeled) Avalia connectors.  (The avalia
connectors are like half of a jumper).  The ASUS mobo is designed for
AMD, which might explain why it does not support HD Audio.  In any
case (pardon the pun), you have answered all my questions beyond
expectation.  Many, Many thanks!  Bob

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