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| Pre-amp to connect microphone to speakers |
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| SoundFan:
--- Quote from: Audioguru on November 29, 2018, 04:54:01 pm ---An electret mic has a diameter of 6mm or 9.7mm. In old cell phones they were half that and in new cell phones they are a tiny little spec. I have a very small speaker (squeaker) that is 25mm in diameter that was in over-the-ears headphones. My very small speaker also works as a microphone but has no Jfet in it like an electret mic has so it has no polarity and works both ways like yours. Then you do not have an electret mic, yours is a dynamic mic that is a little speaker with a magnet on the back of it. A dynamic mic does not need and does not want the resistor used to power the Jfet in an electret mic. Try removing the resistor that powers your mic to see if it works much better without it. Here are some photos of electret mics: --- End quote --- Those are electret mics, and I do also have an electret mic. I will use one like in your photos with polarity, then it will be easier to assure it to be working with the same circuits. Until now changing the direction of the mics didn't seem to have helped though unfortunately. |
| Audioguru:
You said that your electret mic works on your pc and on the LM393 circuit so it must be fine and the problem is with your opamp preamp and LM386 power amp circuit. Do you see on your mic where one pin connects to its metal case? Measure it with an ohm meter if you can't see it. That is the ground pin. |
| Zero999:
--- Quote from: SoundFan on November 30, 2018, 09:01:49 am --- --- Quote from: Audioguru on November 29, 2018, 04:54:01 pm ---An electret mic has a diameter of 6mm or 9.7mm. In old cell phones they were half that and in new cell phones they are a tiny little spec. I have a very small speaker (squeaker) that is 25mm in diameter that was in over-the-ears headphones. My very small speaker also works as a microphone but has no Jfet in it like an electret mic has so it has no polarity and works both ways like yours. Then you do not have an electret mic, yours is a dynamic mic that is a little speaker with a magnet on the back of it. A dynamic mic does not need and does not want the resistor used to power the Jfet in an electret mic. Try removing the resistor that powers your mic to see if it works much better without it. Here are some photos of electret mics: --- End quote --- Those are electret mics, and I do also have an electret mic. I will use one like in your photos with polarity, then it will be easier to assure it to be working with the same circuits. Until now changing the direction of the mics didn't seem to have helped though unfortunately. --- End quote --- Do yo have a schematic for the LM393 amplifier circuit? I've never seen an audio amplifier based on that IC before. I wonder if it's class D? Or perhaps you've got the part numbers mixed up or there's a printing error and it's really the LM386? |
| Audioguru:
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". |
| Audioguru:
I found this in Google: |
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