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electret mic preamp questions

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This is what I have working so far. It is good enough to do the voice recording that is on my plate.

I removed the cap and change R4 to 150K. I removed the audio taper on the output.


For now it is in a plastic box. Need to find a metal one that will also hold the 9V battery. Or maybe use a plastic one and wrap the preamp in grounded alu foil.

The attachment is short zipped wave file recorded with it.
 

Attachments

  • try.zip
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Your preamp works fine.
The microphone picks up background noise that sounds like furnace air or air-conditioning.
 
The Eagle Project

A few people have contacted me about building one of these. This is not the worlds best mic preamp but it is simple to build and works well. I think the sound quality is better then that of a cheap commercial mic.

Attached you will find a zip of the project in Eagle format. Open it and take a look at it even if you use the supplied PCB artwork. It ties the schematic and the PCB together.

With Eagle you need to use the rat-nest tool prior to printing to fill the ground plane.

Previous posts in this thread contains info on what parts to change, so it will amp a electret mic to LINE level which is preferred to using the MIC input.

Mine works well for voice in small plastic case that is attached to my headset with black tape. One of the two pin headers is for attaching a audio taper. I have a shorting block over it.

Again this circuit design is not original with me.
Thanks again to Audiogru and others for the help.
 

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  • SSEMP_4_NET.zip
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  • PCB.png
    PCB.png
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  • PCB_place.png
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Hello, What would be the easiest way to make the same electret mic preamp that 3v0 , has and make it stereo with one input, one output using one 9volt battery? Thank you!
 
Hello, What would be the easiest way to make the same electret mic preamp that 3v0 , has and make it stereo with one input, one output using one 9volt battery?
One input and one output is mono, not stereo.
Stereo has two inputs and two outputs.

Maybe you want to mix the two stereo channels into mono to feed the mono preamp? Then make a mic mixer circuit.
It might be easier to make two mic preamps then mix together their outputs with two resistors.

One 9V battery can power many mic preamps.
 
3v0,

Why is C5 there? (The 2pF cap) I did a quick calculation and it should roll off the high end starting at 2.4MHz. The response of the TL07* only goes to ~3MHz.

I like your idea of gluing and grounding Al foil inside a plastic box for shielding. I have an old Radio Shack autoranging DMM built that way from the factory.
 
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