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How to amplify signal from a microphone and filter frenquency of voice?

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river78

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Have some one know how to amplify signal from Microphone and filter frenquency of voice.
Thanks
 

IanP

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Re: Microphone amplifier

Firstly, you will need an amplifier which can work with different types of microphones .. picture 1.
As a "voice" filter you can consider a combination of passive and active LPFs (Low Pass Filter) .. picture 2.
As you don't need much gain in this stage, replace 680kΩ resistor with ≈10kΩ ..
This filter has been calculated for "telephone" band, which is ≈300Hz-3kHz ..

Regards,
IanP
 

river78

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Re: Microphone amplifier

thanks
But that is very difficult to creat a solenoil whith an exactly value. so could u send me another circuit?
thanks a lot!
 

IanP

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Re: Microphone amplifier

470µH RF choke (inductor) is sold as off-the-shelf item and can be obtained for less than $0.5, for example from here:
**broken link removed**
If you are worried about this inductor you can replace it by, say, 100-470Ω resistor, which will be not as effective as an inductor, but should work satisfactorily ..

Regards,
IanP
 

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