This mic preamp circuits based LM358 is very easy to build, and can operate with 9VDC battery, so that it becomes a practical preamp circuit and have very small dimensions.
Potentiometer R5 serves to adjust the gain feedback from LM358 IC. Adjust R5 to get the best output signal out of noise and not too big.
Mic PreAmp Circuits Note:
- Use R5 to set the gain of the Op-Amp 358
- If you want to create a stereo mic preamp circuits, you do not need to use two ICs, just one IC alone. Because inside IC LM358 has two op-amps.
- Use a PCB layout with a good grounding system.