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How do i wire a condenser mic into my audio input of my PC/Computer?

Ok, I answered it myself but I looked long and hard so hear is one option for connecting a condenser mic to a pc. This is 20 year old microphone that shipped with my family's Apple LC in 1992.  The mic works well with one of my laptops audio card...

Not sure what the Zenner diode value is but its probably pretty small. I measured the voltage across the mic + to ground and it was 3.5volts.

I saw another guy that only found a diode on his condenser mic so maybe newer audio cards can work without all the extra parts...


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It seems like I answered this question before. I have no idea how to search through my previous answers, but I did find this: https://www.instructables.com/files/orig/FHZ/YTV8/GAPUWXXX/FHZYTV8GAPUWXXX.jpg
in my image library.  And it looks kind of self-explanatory.  Its just a computer microphone I took apart one time, and some notes on what wire goes where.  I am guessing the solitary diode on mine is just a silicon small signal diode, but I did not examine  it closely.

mic-wiring.jpg
hydronics (author)  Jack A Lopez5 years ago
Hey Jack, Yea, I saw your post. I even linked to it above. It would be really interesting to see what that diode is, eh? I mean I tried to hook the condenser mic directly to my PC input and it sounded like crap so the diode is a necessary component. My small PCB has a Z next to its diode... so I thought it was maybe a zinner diode. It would be nice to know what the value and type of your diode is.. Whats the difference between an zinner diode and a signal diode as they relate to audio recording? I guess there is always trial and error.
At first I was thinking that the function of this diode was simply as a clipper
http://en.wikipedia.org/wiki/Clipper_(electronics)
to keep the output signal in a certain range.

If the diode is just there as a clipper, then I would expect the microphone would sound good without it, just as long as the signal level is small.

But maybe it is there as a voltage regulator, keeping the voltage to the condenser mic's pre-amp constant?

I'll see if I can dig up that old computer mic and see what exactly, what kind, of diode that is.

The difference between a Zener diode
http://en.wikipedia.org/wiki/Zener_diode
and an ordinary diode is that the Zener has been designed to have its reverse-breakdown voltage be small and precice.  Also Zener diodes are specified in terms of this reverse breakdown voltage.  E.g. you expect something sold as a "5.1 volt Zener diode" to have its reverse breakdown occur at -5.1 volts.

If you look at a graph of I vs V for a diode,
http://en.wikipedia.org/wiki/File:V-a_characteristic_Zener_diode.svg
you'll notice that the forward conduction region kind of looks like the reverse breakdown region.  Both have a strong upward slope.  The difference is that the reverse-breakdown region occurs over a more narrow range of voltage, so that region is better if you are trying to use this voltage as the basis for a voltage regulator. 

In contrast,  for building voltage clippers, you don't always need the clipping action to be precise.  So that's why I was guessing the diode attached to that microphone might be an ordinary diode.
I took that computer microphone apart again, and I examined the diode, and it had the characters "1N4148" printed on it. So that means it's just an ordinary silicon diode.

Again I am guessing its function there is protective somehow, but not necessary for the microphone to function.
hydronics (author)  Jack A Lopez5 years ago
thanks a lot. I appreciate your help trying to understand this. Here is another diagram I found using a 0.1uF capacitor in lieu of the diode in yours.

http://www.schematicwiringdiagram.com/microphone-pc-circuit
Microphone-PC-Circuit.gif
rickharris5 years ago
A condenser mike needs a power supply. 1.5 to 3 volts often.
hydronics (author)  rickharris5 years ago
Yes that is true. So in this case as in all small peripheral PC condenser mics... the power supply originates from the sound card. Kinda interesting, eh?
Regarding the powering of these condenser microphones,  I have a diagram that sort of shows how these are intended to be connected, here:
https://www.instructables.com/files/orig/FNK/I1XX/G8TCO55N/FNKI1XXG8TCO55N.png

That is, that circuit shows how you would wire up a condenser mic to something other than a computer sound card.  Presumably the sound card has something like that circuit built into it already; e.g.  DC power flows to the mic through the resistor.  AC signal flows out through the capacitor.

I found that picture in my image library, but I don't remember where I found it before that.  Guessing that the unlabeled resistor in that picture has a value of about 10 K (10 000 ohms).

I probably found it here:
http://www.google.com/search?tbm=isch&hl=en&q=condenser+microphone+circuit+diagram
There might be other pictures there providing  clues as to how to wire up a condenser microphone.