What type mic is my P5B-E mb expecting?

I'm using this headset with the HC-6 mic element:

http://www.heilsound.com/amateur/products/proset/#1

I just tried to connect this headset to my old P5B-E motherboard and
find that the mic audio level is very low. The mic works fine with my
ham gear and my old R51 Thinkpad laptop, so it's working.

No software adjustments will improve the audio, although I can reduce
the level even more.

The mic is dynamic, with a nominal impedance of 600 ohms. I don't see
any mention in the manual of what sort of mic the MB expects.

Is this just the wrong sort of mic, are there some jumpers or BIOS
settings I've missed, or is something broken?

--
St. Paul, MN

Bert wrote:
I'm using this headset with the HC-6 mic element:

http://www.heilsound.com/amateur/products/proset/#1

I just tried to connect this headset to my old P5B-E motherboard and
find that the mic audio level is very low. The mic works fine with my
ham gear and my old R51 Thinkpad laptop, so it's working.

No software adjustments will improve the audio, although I can reduce
the level even more.

The mic is dynamic, with a nominal impedance of 600 ohms. I don't see
any mention in the manual of what sort of mic the MB expects.

Is this just the wrong sort of mic, are there some jumpers or BIOS
settings I've missed, or is something broken?


The motherboard expects something other than a moving coil microphone.

Moving coil (dynamic) might be 2 to 3 mV or so. The AC'97 or HDAudio chips
don't have enough gain for that, even if the 20dB boost is engaged.
There is even one HDAudio chip, where some idiot "forgot" proper
boost altogether (no evidence of good gain range in the
datasheet - could be a datasheet error). I'm not aware of
later designs repeating that error.

A ceramic microphone (piezoelectric), can put out about 100mV.
That should be OK.

But what the motherboard is really designed for, is electret
microphones. Computer audio has a DC bias voltage source (somewhere
in the 3V to 5V range). The bias source connects via a limiting resistor
(1K to 2K), and that is the power source for the microphone. The idea is,
such a power source is not supposed to upset the other kinds
of microphones. (In theory, there may be a register in the
HDAudio chip to turn off the bias source, but in practice
it isn't exposed so a user can do that. Older designs, like
the AC'97 era, the bias source may have been external to
the chip, and not under software control. Such a source might
be 5V.)

Even stereo microphones are handled this way, with DC bias on
both left and right. So it's not like a three contact 1/8" plug
has power on one pin, and microphone signal comes out on the other.
In fact, on a mono microphone, the microphone end shorts left and
right together, so any bias source is connected to the output signal
anyway.

+----------------- L-ADC
| +--------- R-ADC
| |
Vbias | Vbias | GND
| | | | |
1K | 1K | |
| | | | |
+---+ +---+ |
| | |
TIP RING SLEEVE (Jack)
L-MIC R-MIC GND

Now, the puzzling part, is the last time
I looked in a catalog, there were some
electrets that seemed to need 5V. And some
of the audio chips don't have 5V as an option.
Yet you don't hear a lot of complaints, which
means the electrets used in computer mic/headsets
must be selected to work with the lowest common
denominator.

There is a picture of the typical electret
setup here. The DC blocking capacitor, already
exists on the inputs of the HDAudio chip. (Everything
on HDAudio is AC coupled.) I didn't bother to show
that cap in the above ascii-art.

http://en.wikipedia.org/wiki/Electret_microphone

Since the Heil document I downloaded, doesn't
have any technical tidbits, I can't translate
what they're telling me, into anything useful.

The input impedance on the motherboard, for
microphone in or for line in, should be 10K ohm
or greater. So not a problem when dealing with
a 600 ohm source.

If the microphone doesn't work when plugged into
your stereo, your stereo probably won't have a
bias source on it.

Paul

In Paul wrote:

A ceramic microphone (piezoelectric), can put out about 100mV.
That should be OK.

But what the motherboard is really designed for, is electret
microphones.

Thanks. Looks like a little change in plans is called for.

--
St. Paul, MN

Bert wrote:
In Paul wrote:

A ceramic microphone (piezoelectric), can put out about 100mV.
That should be OK.

But what the motherboard is really designed for, is electret
microphones.

Thanks. Looks like a little change in plans is called for.


I can't really be sure what kind of microphone is
involved there. There seem to be too many adapters.

Paul

In Paul wrote:

Bert wrote:
In Paul wrote:

A ceramic microphone (piezoelectric), can put out about 100mV.
That should be OK.

But what the motherboard is really designed for, is electret
microphones.

Thanks. Looks like a little change in plans is called for.


I can't really be sure what kind of microphone is
involved there. There seem to be too many adapters.

The adapters are there just to match the seemingly endless variety of
microphone and headphone connectors used on various makes and models of ham
radio gear.

There are only two types of microphone elements, dynamic and an electret.
Mine has the dynamic element.


--
St. Paul, MN

Bert wrote:
In Paul wrote:

Bert wrote:
In Paul wrote:

A ceramic microphone (piezoelectric), can put out about 100mV.
That should be OK.

But what the motherboard is really designed for, is electret
microphones.
Thanks. Looks like a little change in plans is called for.

I can't really be sure what kind of microphone is
involved there. There seem to be too many adapters.

The adapters are there just to match the seemingly endless variety of
microphone and headphone connectors used on various makes and models of ham
radio gear.

There are only two types of microphone elements, dynamic and an electret.
Mine has the dynamic element.

If so (really is dynamic, moving coil), you might benefit
from a separate amplifier.

And picking an amplifier, isn't exactly easy. This is why,
an ideal audio product, would already have a preamp built in.

It might actually be easier to just switch to another microphone.
If one of these boxes costs $100, it might be easier to just find
an electret microphone for computer usage.

http://www.m-audio.com/products/en_us/AudioBuddy.html

Be aware, that even so-called "reputable" computer product
makers, make crap. I have a Logitech headset with microphone,
where the only way you can get audio output from the microphone,
is by scratching the microphone surface with your thumbnail.
It is *that* insensitive. It cannot possibly be used for voice
input.

My best microphone, is an Apple Plaintalk (oval shaped) one.
There is an Apple microphone which is a circular disc, which
is terrible. The oval shaped one has a separate 5V power
supply, to run a tiny 4 pin amplifier chip inside the microphone.

This won't work on a PC directly, due to the weird plug on the end.
I think the 5V goes on the end contact.

http://www.amazon.com/Apple-M9060Z-A...alk+microphone

An Andrea Superbeam is another option. It's a stereo microphone,
that with an appropriate driver, uses beamforming to do more
directional recording of a mono source. Some motherboard
sound drivers, used to have a provision to work with one
of these. This is two electrets and stereo wiring.

http://www.amazon.com/Andrea-Array-2...uperbeam+array

They also sell those with a USB adapter, bypassing the
computer audio path entirely, and making it a USB microphone.

http://www.amazon.com/Andrea-Electro...owViewpoints=1

Paul

In Paul wrote:

It might actually be easier to just switch to another microphone.
If one of these boxes costs $100, it might be easier to just find
an electret microphone for computer usage.

Exactly so. There are lots of headsets made specifically for this
application. They're cheap and easy to find.

--
St. Paul, MN

Bert wrote:
In Paul wrote:

It might actually be easier to just switch to another microphone.
If one of these boxes costs $100, it might be easier to just find
an electret microphone for computer usage.

Exactly so. There are lots of headsets made specifically for this
application. They're cheap and easy to find.


See if you can find the "Boost" tick box for Microphone
and maybe there will be enough gain. They like to
use creative techniques to hide this tick box from the
user.

https://sites.google.com/site/danlas...PAGE-large.jpg

For SoundMax (and perhaps your P5B-E), it would
look like this.

http://img17.imageshack.us/img17/4029/mics.png

Paul

In Paul wrote:

See if you can find the "Boost" tick box for Microphone
and maybe there will be enough gain.

Tried that, wasn't enough.

--
St. Paul, MN