Guillaume said:
Hi again,
On my mobo, here are the two possible definitions for the audio front
panel connector:
first one
---------
port1L GND
port1R Presence
port2R sense1 return
sense_send nc
port2L sense2 return
second one
----------
mic2 agnd
micpwr nc
lineout R nc
nc nc
lineout L nc
But, my 7 wires are labelled:
return L
return R
speakout L
speakout R
mic BIAS
mic in
gnd
What is the good association ???
Thanks a lot by advance,
Guillaume.
Use the second definition. The second definition is the
AC97 header definition, while the first one is the HDAudio
definition. Your wiring is AC97, and lacks sense contacts.
return L (not needed on an HDAudio motherboard with AC97 header)
leave this wire disconnected
return R (not needed on an HDAudio motherboard with AC97 header)
leave this wire disconnected
speakout L = lineout L
speakout R = lineout R
mic BIAS = micpwr
mic in = mic2
gnd = agnd
Mic in is Tip, Mic Bias is Ring, Ground is sleeve, on a microphone.
Just because there is a contact called Mic Bias, doesn't mean that
is the only pin with bias. On a stereo microphone, both Tip and
Ring have bias on them.
+3.3V ---- 2Kohm ----- Tip ----> To ADC, left microphone channel
+3.3V ---- 2Kohm ----- Ring ----> To ADC, right microphone channel
So that's a typical connection setup, for a stereo microphone.
On a mono microphone, the microphone internal wiring may
short Tip and Ring together, so that some bias gets
joined to the input pin. Bias is used to power electret
microphone devices.
http://en.wikipedia.org/wiki/Electret_microphone
In the equivalent circuit here, the capacitor is already on the
motherboard. Which is why no cap is required inside the microphone.
And the bias source, the resistor to V+, is also provided by
the motherboard. On an HDaudio chip, the current source may even
be inside the chip itself. (I think bias can be turned on and off
in software - dynamic jack detection allows the driver to turn off
bias, when the jack is used for output.) Whereas in older "true"
AC97 motherboards, a bunch of external circuits, do things like the
bias.
http://upload.wikimedia.org/wikipedia/commons/5/57/Electret_condenser_microphone_schematic.png
HTH,
Paul
