Electret condenser microphone

Thread Starter

crobertsbmw

Joined Sep 7, 2011
28
So I bought one of these microphone's off digi-key.
http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&KeyWords=CMA-4544PF-W&x=0&y=0
I don't know much about them at all. But I was thinking that if I sing into this thing I should at least be able to create some type of a voltage difference on the two leads. I have it hooked up directly to an o-scope and no matter how much audible noise I create I can't seem to get my o-scope to see any signal. What do I need to know about these microphone's in order to make them useful?
 

Thread Starter

crobertsbmw

Joined Sep 7, 2011
28
Now I just feel dumb. I did look at the data-sheet, that is my problem. I should try reading the entire datasheet before I post, then I won't miss things like schematics that are posted. Sometimes I just need someone to help hold my hand. You know what I mean.
 

Audioguru

Joined Dec 20, 2007
11,249
When the electret mic is properly powered then its output level is very low, it needs a preamp with a gain of about 200 to bring the level up to 1V.
 

Thread Starter

crobertsbmw

Joined Sep 7, 2011
28
When the electret mic is properly powered then its output level is very low, it needs a preamp with a gain of about 200 to bring the level up to 1V.
Without amplification I just get a signal of 60hz and a couple milli-voltsno matter how hard I yell. If I amplify this am I really going to see my audio signal? I feel like if I am already seeing a 60hz signal (that I am assuming is ambient) without any amplification over any audio signal then amplifying it won't help.
 

SgtWookie

Joined Jul 17, 2007
22,210
You have 60-cycle hum from your supply. I'll bet you're trying to use an unregulated wall wart; they won't work very well.

Here's a preamp for an electret mic; AudioGuru posted almost this exact same circuit a few years back. VR1 should be 500k instead of 470k.
 

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Audioguru

Joined Dec 20, 2007
11,249
The electret mic needs to be connected to the preamp with a shielded audio cable because ordinary wires will pick up mains hum radiation.
 
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