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Pre-amp to connect microphone to speakers

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SoundFan:
Hello,

I am trying since a few days to make a good microphone pre-amp to connect my electret microphones to a speaker or headphones. I have tried some Arduino modules like the MAX9814 from Adafruit and a cheap chinese module that uses a transistor and a LM393 comparator. My project will be powered by Li-Po batteries and needs a very good audio quality. These Arduino modules do work but the sound quality isn't good enough. I have tried to make my own pre-amp using some op-amps but none of these worked well (I can only hear some distorted sound when I blow directly into the mic, but I can't hear my voice when I talk).
The mic itself should have enough quality: I have tried connecting it directly to the mic input of my laptop and it sounds great.

Could someone please help me ? I really would like to improve my results.

Zero999:
A power amplifier is required to drive a speaker or headphones.

There's nothing wrong with the MAX9814. It's a perfectly good IC and includes an AGC (Automatic Gain Control) which means it adjusts the volume level automatically to match the sound picked up by the microphone.

The LM393 is not an audio amplifier and is probably one of the worst things you can use. An op-amp won't be able to drive a speaker. It will current limit and give a distorted output. A common IC is the LM386, but it's fairly low powered.

What are your output power requirements? How big is the speaker?

SoundFan:
@Hero999 First of all, thanks for your quick reply!
I'm driving a very small 0.5W and 8 ohm speaker.
You are right, the LM393 is totally inappropriate for the job but unfortunately the max9814 also doesn't work well in my project somehow (it is almost as bad as the transistor preamp with LM393).
I won't be needing much energy at all. This 0.5W speaker and headphones are the only things I want to connect to the output. And even those won't be connected simultaneously.

IanB:
I have this page in my bookmarks list:

http://www.techlib.com/electronics/audioamps.html

You may find something useful here?

Richard Crowley:
Remember that electret condenser microphones require power (some call it "bias" but that is improper).
Your computer provided the ~5V "plug-in power" when you tested it there.

Here are a few examples of circuits which provide the power supply to the electret mic....









Those circuits will work with most modern op-amps, so the specific numbers on the above schematic diagrams are only suggestions.

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