Electronics > Beginners

Cheap microphone - simple amp circuit

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mikeinfodoc:
I very new to audio circuits.

I created a very simple audio amplifier circuit based on the NE5532 (using a split single DC supply)
  which I am testing with a simple signal generator for the ac input, and a small pc speaker on the output.

http://www.ti.com/lit/ds/symlink/ne5532.pdf

In my tests, I am sending in a .05 V input sine wave
 and getting a fairly clean 5 Vpp sine wave on the output
   (which sounds as I would expect on the pc speaker  ....I tested ranges of 2khz to 8khz frequency)

That said,

I was hoping to use this same small test circuit, to see if I can amplify input signals from a super cheap pc microphone such as this one:

https://www.cdw.com/product/Cyber-Acoustics-ACM-51B-Desktop-Microphone/1755669?pfm=srh



I noticed that the microphone website lists its input and output impedance of 2k ohms

However, I am wondering if any cheap microphone (such as the one linked above) would produce enough millivolts to be picked up by my circuit.

I welcome wisdom/guidance.

As I do not know how many milli volts typically can generated directly from a cheap microphone.

tpowell1830:
Your posted link takes me to a news report, not to a microphone.

Buriedcode:
I'm thinking you have linked the wrong link - thats a quack website for conspiracy theories (at least it looks like that to me).

With an output impedance of 2k I think you may be talking about an electret mic.. but I@m just guessing here.  If your circuit does indeed have a gain of 100 (50mV p-p in, 5v p-p out) thats a gain of 40dB which is quite high and should be more than enough to amplifier even the lowest output microphones.  Most PC inputs have around 20dB gain.

mikeinfodoc:
Indeed I did not mean to post about Nancy Schaefer (however that is indeed a very interesting story in and of itself).

I corrected the link above for a sample inexpensive pc mic.

Audioguru:
The NE5532 is an opamp, not a power amp. Its datasheet says that its minimum load is 600 ohms but most speakers are 8 ohms that need much more current than an opamp can provide.

The spec's for your microphone say that it is an electret type that is very common today. Its output is about 10mV when 10cm away from your mouth and you are talking at a conversation level. One resistor value sets the gain of the amplifier, 200 is very sensitive but 500 is more sensitive. High sensitivity causes an amplifier to make severe distortion when a normal sound level is at the microphone, and to cause acoustical feedback howling if the microphone can hear the sounds from the speaker.

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