Lazy Man's PC microphone adapter
 

I would say that a PC mic is putting out a mic, not a line level. Line
levels are about 500 - 2000 mV, while a mic level is more like 10 - 100mV.
Your scheme won't work without a mic preamp. Also, I may be wrong here, but
I'm pretty sure that a PC mic is a condenser, which means it needs some
power (1.5-12V) to work, which it is probably getting from the mic input on
the soundcard.

You can verify this by putting a DC voltmeter on the output of your
soundcard, and you can verify the input level problem by plugging your PC
mic into the line input of your card.


"JURB6006" wrote in message
...
Hi;

I think I know what's going on with my failing soundcards, the last victim
was
an AWE64 :(, but I saw corrosion in some on the IC pins. How it got there
I
still don't know, but that's not the topic of this post..

I would like to record more than one microphone channel on my PC and I
think I
got a hassle free way to do it.

What I need to know is what level the mike puts out to the soundcard. I'm
assuming (that's why I thought I better ask) that the microphone's
internal
preamp puts out approximately line level. I think this because if you
design
some standards for this system, and you have a powered preamp, why not
eliminate extra stages on the card right ?

To be lazy as possible I want to take a Y adapter from the mic input,
stereo
adapters to two other adapters that will distribute the power to all three
mics
and send the outputs 1.to the orig mic input, 2 left and right each to the
line
input. There would be three mics, but I'm pretty sure power wouldn't be a
problem with these flea power preamps.

Can anyone confirm that PC mics put out approx. line level to the
soundcard ?
If so all I need is some adapters and I can get this done without
soldering.
Three channels, it would be great, even though I can't post-mix.

Thanks in advance

JURB


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JURB6006 ) writes:
Hi;

I think I know what's going on with my failing soundcards, the last victim was
an AWE64 :(, but I saw corrosion in some on the IC pins. How it got there I
still don't know, but that's not the topic of this post..

I would like to record more than one microphone channel on my PC and I think I
got a hassle free way to do it.

What I need to know is what level the mike puts out to the soundcard. I'm
assuming (that's why I thought I better ask) that the microphone's internal
preamp puts out approximately line level. I think this because if you design
some standards for this system, and you have a powered preamp, why not
eliminate extra stages on the card right ?

To be lazy as possible I want to take a Y adapter from the mic input, stereo
adapters to two other adapters that will distribute the power to all three mics
and send the outputs 1.to the orig mic input, 2 left and right each to the line
input. There would be three mics, but I'm pretty sure power wouldn't be a
problem with these flea power preamps.

Can anyone confirm that PC mics put out approx. line level to the soundcard ?
If so all I need is some adapters and I can get this done without soldering.
Three channels, it would be great, even though I can't post-mix.

You misunderstand what the "preamp"in the microphone is for. It's merely
as single stage source follower to match the very high impedance of
the actual electret microphone to much lower output impedance.

You can actually open up an electret capsule and see this. At least when I
took one apart, there was an identifiable FET in a small package, and if
that wasn't all there was then there was also a resistor.

Since that FET is only there for impedance matching, theoretically
a transformer could be used there. But it would be much bulkier,
and prone to pick up hum. So they use a solid state device, and hence
need a very tiny amount of power to run it.

There is no way that this stage with no voltage amplification could provide
a line level voltage. It's merely what comes out of the microphone, and
that will need to be amplified.

So you will need external preamps for thos project.

Micahel

Thank for setting me straight here guys. I guess I'll have to figure out
something else.

JURB