Electronics > Beginners
Pre-amp to connect microphone to speakers
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SoundFan:
I will use the electret mics with polarity from now on.

The LM393 circuit is a clap module but not the one that AudioGuru is referring to (mine has only 3 pins). I do also have the 4 pin version but that doesn't work with headphones. And oddly enough, its quality is quite good for a clap sensor (but still not good enough)
Zero999:

--- Quote from: Audioguru on December 01, 2018, 02:39:03 pm ---I think there is another website forum about this circuit or it was in a "conversation" with me. I saw the schematic with the LM393 and I commented that it was probably a "hands clap detector".

--- End quote ---

--- Quote from: Audioguru on December 01, 2018, 03:08:33 pm ---I found this in Google:

--- End quote ---
Then the LM393 is not being used as an amplifier, but a comparator. It will not drive a speaker, unless you just want it to make a click, when it picks up a sound.
Audioguru:
The LM393 plays audio with lots of "overdrive" (because it has very high gain and no negative feedback) producing severely distorted squarewaves. Like acid rock "music".
I think the transistor preamp had a lowpass filter to cut high audio frequencies letting the clipping from the LM393 produce the severe distortion.
Teledog:
Was looking for the same sort of schematic.
A real PITA to build.
Do an eBay search for "DC 3.7V-6V MIC AMP MAX9812L+TDA1308 Stereo Microphone Headphone Amplifier Module"
Works like a charm! (only used cheap earbuds, but can go to an extremely high volume)
There is already a DC bias on the electret mic input.
Just plug in your electret mic, battery & headphones (small speaker?)  & good to go.
An AC->DC  wall wart DOES cause a hum though..battery power is quiet.
SoundFan:

--- Quote from: Hero999 on December 01, 2018, 07:50:38 pm ---Then the LM393 is not being used as an amplifier, but a comparator. It will not drive a speaker, unless you just want it to make a click, when it picks up a sound.

--- End quote ---
In my case it seems to be working as an amplifier, it really does output sound. I can even hear my voice with it.


--- Quote from: Audioguru on December 01, 2018, 08:10:24 pm ---The LM393 plays audio with lots of "overdrive" (because it has very high gain and no negative feedback) producing severely distorted squarewaves. Like acid rock "music".
I think the transistor preamp had a lowpass filter to cut high audio frequencies letting the clipping from the LM393 produce the severe distortion.

--- End quote ---
That will probably be a problem, I really wish to get a good sound quality.


--- Quote from: Teledog on December 02, 2018, 01:23:49 am ---Was looking for the same sort of schematic.
A real PITA to build.
Do an eBay search for "DC 3.7V-6V MIC AMP MAX9812L+TDA1308 Stereo Microphone Headphone Amplifier Module"
Works like a charm! (only used cheap earbuds, but can go to an extremely high volume)
There is already a DC bias on the electret mic input.
Just plug in your electret mic, battery & headphones (small speaker?)  & good to go.
An AC->DC  wall wart DOES cause a hum though..battery power is quiet.

--- End quote ---
This module seems to be exactly what I've been looking for ! I just bought it and will give feedback about it when it arrives.
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