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I've encountered a problem. I recently bought a condenser microphone and I wanted to have some fun, so that if I said something into the microphone, I'd hear myself in the small 8 Ohm 0.5W speaker.

I have used an LM386L amplifier and there seems to be no sound at the output. It seems like it's not amplifying anything at all. Here's the circuit on the breadboard:

photo of breadboard

enter image description here

What I have basically done is:

  • I took an output from the microphone and put it on pin 3 of LM386L.
  • Pins 2 & 4 are all connected to ground.
  • I used 10 uF between pin 1 and 8 to obtain a proper gain.
  • On pin 7 I used another 10 uF capacitor.
  • Pin 5 represents the output of the amplifier, where I put 100pF ceramic capacitor in parallel to the 600uF electrolytic capacitor and 8 Ohm speaker to get rid of all unwanted frequencies. 600uF capacitor should get rid of any DC voltage.

When I talk into the microphone, nothing happens although when I connect it to oscilloscope, I see a voltage, so the microphone works. I'm powering it with 5V.

If anyone knows the solution, please help me. And do not mind the soldered pins on the female jack.

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    \$\begingroup\$ Does it amplify anything from other sources? What powers the microphone? Can you please draw this as a schematic? \$\endgroup\$
    – Justme
    Oct 2, 2019 at 19:10
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    \$\begingroup\$ Even with an AC short between pins 1 and 8, the gain is still only 200, which is probably not enough to take mic level all the way to speaker level. \$\endgroup\$
    – Dave Tweed
    Oct 2, 2019 at 19:14
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    \$\begingroup\$ If it's an electret mic, have you biased it correctly? ( 4K7 to +9V will probably do, and a DC blocking cap to the amp) See any "electret mic" circuit for details \$\endgroup\$
    – user_1818839
    Oct 2, 2019 at 19:38
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    \$\begingroup\$ Please add the full mic circuit to the rest of the circuit you have already. \$\endgroup\$
    – Aaron
    Oct 2, 2019 at 19:50
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    \$\begingroup\$ Condenser microphones require a bias voltage. \$\endgroup\$
    – JRE
    Oct 3, 2019 at 7:30

1 Answer 1

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Googling "condenser microphone circuit" shows lots of schematics that have three things yours is missing

As does the image in this Question on biasing a condenser mic

  • Where does the other side of your mic connect?
  • What is your biasing?
  • Where is your DC blocking cap?

enter image description here

I've used the LM386 to power 8Ω woofer speakers, and you will hear audio, once you have your mic set up correctly.

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  • \$\begingroup\$ thanks, I will give it a try tomorrow. \$\endgroup\$
    – MerryGR
    Oct 3, 2019 at 19:31

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