K8N - no audio out rear port

  • Thread starter Thread starter cranbrook
  • Start date Start date
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cranbrook

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?

Thanks
 
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?

Thanks
Click to expand...

Carefully recheck the wiring for the front panel. If it is not correct,
the back panel audio will not work.
 
KLH said:
Carefully recheck the wiring for the front panel. If it is not correct,
the back panel audio will not work.
Click to expand...

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.

HTH,
Paul
 
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.
 
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.
 
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.
Click to expand...

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)
http://www.epanorama.net/circuits/microphone_powering.html

/ \
| | 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
contact.)

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:

http://www.pcplanets.com/item.asp?item=633

HTH,
Paul
 
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