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A7V880 and Creative microphone

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  • Asus
  • Microphone
  • Creative
  • Motherboards
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Anonymous
a b V Motherboard
April 24, 2005 4:42:26 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

Hello everyone!

I'm having problems using a Creative microphone (I got it with my former
Sound Blaster card) with the AD chip integrated in my Asus A7V880 mainboard.
First of all, my case has a front panel micrphone connector with three wires
named as follows:

/ \
MIC_DATA --------| |
\ /
+===+
MIC_VCC --------| | 3.5mm plug
|===| to soundcard
| |
GND --------| |
| |
+=======+
| |

I checked the above connections with a ohmeter. The pins are not shorted in
any way inside the front panel connector circuitry.

Now, my Asus mainboard has a FP_AUDIO connector with the following pinout:

BLINE_OUT_L . . LINE_OUT_L
. NC
BLINE_OUT_R . . LINE_OUT_R
+5VA . . MICPWR
AGND . . MIC2

The upper pins are for incoming and returning audio stereo signal (for front
panel headphone connector) and they work OK.
The first thing I did was connecting the mic wires this way:

MICPWR <-> MIC_VCC
MIC2 <-> MIC_DATA
AGND <-> GND

This way, the Creative microphone does NOT work (not even a weak signal,
nothing), while another microphone I have (one of those small clips on
headphones) works like charm.
Searching the net I found that Creative uses particular mics that require
power in order to work.
Keeping the aforementioned connections, I tested voltages on the front panel
mic jack.

/ \
tip (T) --------| |
\ /
+===+
ring (R) --------| | 3.5mm plug
|===| to soundcard
| |
sleeve (S) --------| |
| |
+=======+
| |

The SR and ST voltages are 5.02V, while the RT voltage is 0.00V.
Now, I was surprised to find that tip and ring have equal bias while no
microphone is connected.
I tried to connect MICPWR to +5VA, resulting in:

+5VA <-> MIC_VCC
MIC2 <-> MIC_DATA
AGND <-> GND

The results were exactly the same: ring and tip biased +5.02V.

As a test, I temporaily connected my old PCI Sound Blaster and read the
voltages on its microphone port: SR is 5.02V, but ST is 0.00V. When
connected to the old SB both my microphones work perfectly.

Now, what's the problem and how to solve it? Is it a strange issue of the
creative microphone? Or maybe it's the mobo's fault since MICPWR and MIC2
look shorted (same bias)?

Thanks in advance.

--
Merak

More about : a7v880 creative microphone

April 24, 2005 4:42:27 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <MKKae.5659$ms1.1666@tornado.fastwebnet.it>, "Merak"
<me@anywhere.net> wrote:

> Hello everyone!
>
> I'm having problems using a Creative microphone (I got it with my former
> Sound Blaster card) with the AD chip integrated in my Asus A7V880 mainboard.
> First of all, my case has a front panel micrphone connector with three wires
> named as follows:
>
> / \
> MIC_DATA --------| |
> \ /
> +===+
> MIC_VCC --------| | 3.5mm plug
> |===| to soundcard
> | |
> GND --------| |
> | |
> +=======+
> | |
>
> I checked the above connections with a ohmeter. The pins are not shorted in
> any way inside the front panel connector circuitry.
>
> Now, my Asus mainboard has a FP_AUDIO connector with the following pinout:
>
> BLINE_OUT_L . . LINE_OUT_L
> . NC
> BLINE_OUT_R . . LINE_OUT_R
> +5VA . . MICPWR
> AGND . . MIC2
>
> The upper pins are for incoming and returning audio stereo signal (for front
> panel headphone connector) and they work OK.
> The first thing I did was connecting the mic wires this way:
>
> MICPWR <-> MIC_VCC
> MIC2 <-> MIC_DATA
> AGND <-> GND
>
> This way, the Creative microphone does NOT work (not even a weak signal,
> nothing), while another microphone I have (one of those small clips on
> headphones) works like charm.
> Searching the net I found that Creative uses particular mics that require
> power in order to work.
> Keeping the aforementioned connections, I tested voltages on the front panel
> mic jack.
>
> / \
> tip (T) --------| |
> \ /
> +===+
> ring (R) --------| | 3.5mm plug
> |===| to soundcard
> | |
> sleeve (S) --------| |
> | |
> +=======+
> | |
>
> The SR and ST voltages are 5.02V, while the RT voltage is 0.00V.
> Now, I was surprised to find that tip and ring have equal bias while no
> microphone is connected.
> I tried to connect MICPWR to +5VA, resulting in:
>
> +5VA <-> MIC_VCC
> MIC2 <-> MIC_DATA
> AGND <-> GND
>
> The results were exactly the same: ring and tip biased +5.02V.
>
> As a test, I temporaily connected my old PCI Sound Blaster and read the
> voltages on its microphone port: SR is 5.02V, but ST is 0.00V. When
> connected to the old SB both my microphones work perfectly.
>
> Now, what's the problem and how to solve it? Is it a strange issue of the
> creative microphone? Or maybe it's the mobo's fault since MICPWR and MIC2
> look shorted (same bias)?
>
> Thanks in advance.
>
> --
> Merak

1) Use MIC2, MICPWR, GND as your microphone connections. Those
signals are intended for electret microphones.
2) Do NOT use +5VA! It is intended to power a headphone amplifier
mounted in the front of the computer. It has nothing to do
with microphones or speakers. If you are not careful, you will
damage an audio device connected to such a power source.

MICPWR is connected to +5V, but via a current limiting resistor.
MICPWR is safe to use.
3) Contact Creative Labs and ask them for the specification for
the microphone. Tell them the model number of the mic, so they
can look it up. There is no point using the Creative microphone,
unless you know exactly what it needs in order to work.
Creative are famous for making non-standard stuff.

Normal microphone wiring:

MIC2 <-> MIC_DATA (Tip)
MICPWR <-> MIC_VCC (Ring)
AGND <-> GND (Sleeve)

If you wish to experiment, try connecting both the MIC2 and
the MICPWR signals to the MIC_DATA wire. That is typically
what electret microphones are doing anyway. It is possible
the Creative microphone expects bias and output on "Tip".

MIC2 and MICPWR <-> MIC_DATA (Tip)
No Connection <-> MIC_VCC (Ring)
AGND <-> GND (Sleeve)

The nice thing about MICPWR, is it has a current limiting
resistor. That means MICPWR should not damage any microphones
you connect to the computer, assuming in all cases you
connect "Sleeve" to GND. In other words, as long as "Sleeve"
is grounded, you can connect MIC2 and MICPWR to the "Tip"
or "Ring" without having to worry.

This page will help explain why:
http://www.epanorama.net/documents/audio/electret.html

An electret microphone is a two terminal device. The mic
jack is a three terminal device. If you check out the
microphone that works, you may find the microphone shorts
"tip" and "ring" together.

This is quoted verbatim from the epanorama document.

vcc
O
|
/
\
/
\ EQUAL TO REQUIRED IMPEANCE
/ EX.= 1000 Ohm
\
|
| CAPACITOR MOST ANY VALUE 10uF 16v
|---| | + | /
| |---0----| |------- AUDIO OUT
| | | \
| |----O--------------
|---| |
|
-----
---
-

And, this is how I interpret what happens when an electret is
connected to standard Asus microphone jack wiring:

MIC2 + | /
+---- tip --------| |--------- To AC-97 input
|---| | MICPWR | \
| |---+---- ring ----- resistor ----- +5V
| | AGND
| |-------- sleeve ---+---------------- AGND
|---| |
-----
---
-

What happens is, the FET inside the electret, makes a
variable voltage divider with the resistor on the motherboard.
The tip and ring end up with perhaps 2.5V DC when the
sound is quiet. When sound pressure hits the microphone, the FET
modulates the voltage, and the capacitor on the motherboard
only couples the AC component into the AC-97 input.

Note that, some Soundmax chips are intended for use with the
Andrea Superbeam microphone, which is a stereo microphone.
That is basically two microphones, one which is connected
to "tip", the other microphone is connected to "ring".
To power that circuit, there has to be a MICPWR1 and a
MICPWR2, fed separately to "tip" and "ring". The circuit
looks like this:
+5V
Andrea Superbeam |
resistor
|---| | + | /
| |-------- tip --------+--------| |------ left-in
| L | | \
| |
| |---+ +5V
|---| | |
| resistor
|---| | | + | /
| |-------- ring --------+--------| |------ right-in
| R | | | \
| | |
| |---+---- sleeve --------+---------------- AGND
|---| |
-----
---
-
Based on the Andrea Superbeam circuit, you can see why
I suggested to connect both MIC2 and MICPWR to the "tip"
of the Creative microphone. The wiring that prepares for
use with the Andrea stereo microphone, also has to work
with ordinary electrets.

The Andrea Superbeam spec sheet is here. In particular,
read the description next to the word "Connector":

http://www.andreaelectronics.com/pdf_files/ProductSpecs...

" 3.5 mm jack, left mic power and left audio
on ³tip², right mic power and right audio on
³ring². Sleeve common ground. "

To make further progress, you'll have to contact Creative
and get a specification for the microphone. I looked for
this online once before, and was not able to find it.

HTH,
Paul
Anonymous
a b V Motherboard
April 25, 2005 1:14:15 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

> 1) Use MIC2, MICPWR, GND as your microphone connections. Those
> signals are intended for electret microphones.

That's what I did in the first place... I started experimenting with +5VA as
a second trial.

> 2) Do NOT use +5VA! It is intended to power a headphone amplifier
> mounted in the front of the computer. It has nothing to do
> with microphones or speakers. If you are not careful, you will
> damage an audio device connected to such a power source.
>
> MICPWR is connected to +5V, but via a current limiting resistor.
> MICPWR is safe to use.

Thanks for pointing it out: I'll never use +5VA again.

> 3) Contact Creative Labs and ask them for the specification for
> the microphone. Tell them the model number of the mic, so they
> can look it up. There is no point using the Creative microphone,
> unless you know exactly what it needs in order to work.
> Creative are famous for making non-standard stuff.
>
> Normal microphone wiring:
>
> MIC2 <-> MIC_DATA (Tip)
> MICPWR <-> MIC_VCC (Ring)
> AGND <-> GND (Sleeve)
>
> If you wish to experiment, try connecting both the MIC2 and
> the MICPWR signals to the MIC_DATA wire. That is typically
> what electret microphones are doing anyway. It is possible
> the Creative microphone expects bias and output on "Tip".
>
> MIC2 and MICPWR <-> MIC_DATA (Tip)
> No Connection <-> MIC_VCC (Ring)
> AGND <-> GND (Sleeve)

Didn't the voltages read on the SB mic port give you some hints?

Something I wonder: shouldn't the signal pin (MIC2) read 0V? Why does it
read +5V from AGND?
If bias is provided by MIC2, what's the use of MICPWR then?

Tomorrow I'll try the mic with MICPWR and MIC2 shorted and connected to
MIC_DATA and let you know.

--
Merak
Related resources
April 25, 2005 3:49:26 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Paul" <nospam@needed.com> wrote in message
news:nospam-2404050925000001@192.168.1.178...
> In article <MKKae.5659$ms1.1666@tornado.fastwebnet.it>, "Merak"
> <me@anywhere.net> wrote:
>
>> Hello everyone!
>>
>> I'm having problems using a Creative microphone (I got it with my former
>> Sound Blaster card) with the AD chip integrated in my Asus A7V880
>> mainboard.
>> First of all, my case has a front panel micrphone connector with three
>> wires
>> named as follows:
>>
>> / \
>> MIC_DATA --------| |
>> \ /
>> +===+
>> MIC_VCC --------| | 3.5mm plug
>> |===| to soundcard
>> | |
>> GND --------| |
>> | |
>> +=======+
>> | |
>>
>> I checked the above connections with a ohmeter. The pins are not shorted
>> in
>> any way inside the front panel connector circuitry.
>>
>> Now, my Asus mainboard has a FP_AUDIO connector with the following
>> pinout:
>>
>> BLINE_OUT_L . . LINE_OUT_L
>> . NC
>> BLINE_OUT_R . . LINE_OUT_R
>> +5VA . . MICPWR
>> AGND . . MIC2
>>
>> The upper pins are for incoming and returning audio stereo signal (for
>> front
>> panel headphone connector) and they work OK.
>> The first thing I did was connecting the mic wires this way:
>>
>> MICPWR <-> MIC_VCC
>> MIC2 <-> MIC_DATA
>> AGND <-> GND
>>
>> This way, the Creative microphone does NOT work (not even a weak signal,
>> nothing), while another microphone I have (one of those small clips on
>> headphones) works like charm.
>> Searching the net I found that Creative uses particular mics that require
>> power in order to work.
>> Keeping the aforementioned connections, I tested voltages on the front
>> panel
>> mic jack.
>>
>> / \
>> tip (T) --------| |
>> \ /
>> +===+
>> ring (R) --------| | 3.5mm plug
>> |===| to soundcard
>> | |
>> sleeve (S) --------| |
>> | |
>> +=======+
>> | |
>>
>> The SR and ST voltages are 5.02V, while the RT voltage is 0.00V.
>> Now, I was surprised to find that tip and ring have equal bias while no
>> microphone is connected.
>> I tried to connect MICPWR to +5VA, resulting in:
>>
>> +5VA <-> MIC_VCC
>> MIC2 <-> MIC_DATA
>> AGND <-> GND
>>
>> The results were exactly the same: ring and tip biased +5.02V.
>>
>> As a test, I temporaily connected my old PCI Sound Blaster and read the
>> voltages on its microphone port: SR is 5.02V, but ST is 0.00V. When
>> connected to the old SB both my microphones work perfectly.
>>
>> Now, what's the problem and how to solve it? Is it a strange issue of the
>> creative microphone? Or maybe it's the mobo's fault since MICPWR and MIC2
>> look shorted (same bias)?
>>
>> Thanks in advance.
>>
>> --
>> Merak
>
> 1) Use MIC2, MICPWR, GND as your microphone connections. Those
> signals are intended for electret microphones.
> 2) Do NOT use +5VA! It is intended to power a headphone amplifier
> mounted in the front of the computer. It has nothing to do
> with microphones or speakers. If you are not careful, you will
> damage an audio device connected to such a power source.
>
> MICPWR is connected to +5V, but via a current limiting resistor.
> MICPWR is safe to use.
> 3) Contact Creative Labs and ask them for the specification for
> the microphone. Tell them the model number of the mic, so they
> can look it up. There is no point using the Creative microphone,
> unless you know exactly what it needs in order to work.
> Creative are famous for making non-standard stuff.
>
> Normal microphone wiring:
>
> MIC2 <-> MIC_DATA (Tip)
> MICPWR <-> MIC_VCC (Ring)
> AGND <-> GND (Sleeve)
>
> If you wish to experiment, try connecting both the MIC2 and
> the MICPWR signals to the MIC_DATA wire. That is typically
> what electret microphones are doing anyway. It is possible
> the Creative microphone expects bias and output on "Tip".
>
> MIC2 and MICPWR <-> MIC_DATA (Tip)
> No Connection <-> MIC_VCC (Ring)
> AGND <-> GND (Sleeve)
>
> The nice thing about MICPWR, is it has a current limiting
> resistor. That means MICPWR should not damage any microphones
> you connect to the computer, assuming in all cases you
> connect "Sleeve" to GND. In other words, as long as "Sleeve"
> is grounded, you can connect MIC2 and MICPWR to the "Tip"
> or "Ring" without having to worry.
>
> This page will help explain why:
> http://www.epanorama.net/documents/audio/electret.html
>
> An electret microphone is a two terminal device. The mic
> jack is a three terminal device. If you check out the
> microphone that works, you may find the microphone shorts
> "tip" and "ring" together.
>
> This is quoted verbatim from the epanorama document.
>
> vcc
> O
> |
> /
> \
> /
> \ EQUAL TO REQUIRED IMPEANCE
> / EX.= 1000 Ohm
> \
> |
> | CAPACITOR MOST ANY VALUE 10uF 16v
> |---| | + | /
> | |---0----| |------- AUDIO OUT
> | | | \
> | |----O--------------
> |---| |
> |
> -----
> ---
> -
>
> And, this is how I interpret what happens when an electret is
> connected to standard Asus microphone jack wiring:
>
> MIC2 + | /
> +---- tip --------| |--------- To AC-97 input
> |---| | MICPWR | \
> | |---+---- ring ----- resistor ----- +5V
> | | AGND
> | |-------- sleeve ---+---------------- AGND
> |---| |
> -----
> ---
> -
>
> What happens is, the FET inside the electret, makes a
> variable voltage divider with the resistor on the motherboard.
> The tip and ring end up with perhaps 2.5V DC when the
> sound is quiet. When sound pressure hits the microphone, the FET
> modulates the voltage, and the capacitor on the motherboard
> only couples the AC component into the AC-97 input.
>
> Note that, some Soundmax chips are intended for use with the
> Andrea Superbeam microphone, which is a stereo microphone.
> That is basically two microphones, one which is connected
> to "tip", the other microphone is connected to "ring".
> To power that circuit, there has to be a MICPWR1 and a
> MICPWR2, fed separately to "tip" and "ring". The circuit
> looks like this:
> +5V
> Andrea Superbeam |
> resistor
> |---| | + | /
> | |-------- tip --------+--------| |------ left-in
> | L | | \
> | |
> | |---+ +5V
> |---| | |
> | resistor
> |---| | | + | /
> | |-------- ring --------+--------| |------ right-in
> | R | | | \
> | | |
> | |---+---- sleeve --------+---------------- AGND
> |---| |
> -----
> ---
> -
> Based on the Andrea Superbeam circuit, you can see why
> I suggested to connect both MIC2 and MICPWR to the "tip"
> of the Creative microphone. The wiring that prepares for
> use with the Andrea stereo microphone, also has to work
> with ordinary electrets.
>
> The Andrea Superbeam spec sheet is here. In particular,
> read the description next to the word "Connector":
>
> http://www.andreaelectronics.com/pdf_files/ProductSpecs...
>
> " 3.5 mm jack, left mic power and left audio
> on ³tip², right mic power and right audio on
> ³ring². Sleeve common ground. "
>
> To make further progress, you'll have to contact Creative
> and get a specification for the microphone. I looked for
> this online once before, and was not able to find it.
>
> HTH,
> Paul


Awww man is it really worth all the hassle ;-)
April 25, 2005 6:15:02 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <zeSae.6439$ms1.5404@tornado.fastwebnet.it>, "Merak"
<me@anywhere.net> wrote:

<<snip>>
> >
> > Normal microphone wiring:
> >
> > MIC2 <-> MIC_DATA (Tip)
> > MICPWR <-> MIC_VCC (Ring)
> > AGND <-> GND (Sleeve)
> >
<<snip>>
>
> Didn't the voltages read on the SB mic port give you some hints?
>
> Something I wonder: shouldn't the signal pin (MIC2) read 0V? Why does it
> read +5V from AGND?
> If bias is provided by MIC2, what's the use of MICPWR then?
>
> Tomorrow I'll try the mic with MICPWR and MIC2 shorted and connected to
> MIC_DATA and let you know.
>
> --
> Merak

I'm not arguing with your measurements :-)

I just don't understand what is going on.

Why would Asus be putting bias on both tip and ring ? Not all
Soundmax sound drivers are set up for the Andrea Superbeam, so
not all FP_AUDIO headers would necessarily be using dual bias
to handle a stereo microphone. (Many AC97 sound chips are mono,
so it would be natural for those to only have bias connected
to "ring" on the connector.)

This is the Analog Devices AD1888 web page. The selection of
MIC1 or MIC2 is either/or, meaning mono-only recording. So,
there is no reason for biasing both tip and ring.

http://www.analog.com/en/prod/0%2C2934%2CAD1888%2C00.ht...

There is no applications note, so no reference schematic to
look at. (Reference schematics are what I use to guess at
how Asus implements features. Most lazy engineers will copy
a circuit exactly as the chip manufacturer provides it, so
if there are problems with the circuit, the chip manufacturer
is morally responsible. Asus does do certain things their own
way, generally for cost reasons, or to preserve functional
behavior across all motherboards. For example, the clear CMOS
function seems to be done whatever way they feel like.)

I also looked in the AC97_V2.3 spec, and it does not specify
anything with regard to the wiring of input and output jacks.

Your best bets are to contact Creative, to find out if the
microphone is even an electret. If it is some other kind of
microphone, you could be wasting your time on trying to get
it to work. Setting up the wiring on your computer just for
the Creative microphone, could create danger if someone
unfamiliar with your computer plugs something other than the
Creative microphone into your modified mic jack (like plugging
your expensive headphones into a microphone jack with custom
powering on it).

Trying to reverse engineer the motherboard, to see how the
bias is connected, would at least partially answer your question
about finding 5V on both tip and ring. For example, with the
computer unplugged, you could use your ohmmeter between MIC2
and MICPWR, and see if in fact they are shorted together at
the motherboard. As I explained (in my normal, confusing manner),
it is possible for bias and input to be connected to either or
both tip and ring. A mono electret microphone will short tip to
ring for itself. Only in a stereo microphone application, would
it be necessary to have separate independent bias supplies, and
a motherboard designer won't do that, unless the AC97 chip has
a stereo microphone input.

HTH,
Paul
!