I am trying to find a way to amplify the signal from an electret microphone & feed it as an analog signal to a microprocessor to drive LEDs based on sound. If I look at the amplifier ICs they all have differential + and differential - BTL outputs.

Like this:

enter image description here

In this case which output should I be feeding into the analog pin of the MCU?

  • 1
    \$\begingroup\$ If I look at the amplifier ICs they all have differential + and differential - BTL outputs No they don't. For example the LM386 doesn't. And what prevents you from taking the audio signal from the "Audio input" at line level? \$\endgroup\$ Feb 10, 2021 at 8:22
  • \$\begingroup\$ Use an op-amp amplifier. \$\endgroup\$
    – Andy aka
    Feb 10, 2021 at 8:35
  • \$\begingroup\$ If I connect directly to audio input which is an electret microphone, the signals arent strong enough to work with. I used a prototype module with MAX9814 which an Audio Power Opamp, when I looked at chips with the same specs as the MAX, they all had BTL outputs. Hence my confusion. \$\endgroup\$
    – Amorphous
    Feb 10, 2021 at 8:43
  • \$\begingroup\$ @Amorphous. Check out the MAX9812 as it will most probably do the job for your application, and by the way please consider adding the question as "answered" so that others may benefit from similar problems... \$\endgroup\$
    – citizen
    Feb 11, 2021 at 10:26
  • \$\begingroup\$ @citizen Thanks but MAX9812 is quite expensive for the target price. I tried using LM386, exactly the same circuit here : circuitdigest.com/sites/default/files/circuitdiagram/… but with 2 4k7 resistors instead of the potentiometer. Performance was quite a step down than the MAX9814, ofcourse. Any advise on what I can do in this LM386 circuit to make it better? \$\endgroup\$
    – Amorphous
    Feb 12, 2021 at 15:10

1 Answer 1


If you realy had to use the device you show as an amplifier (although it would not be suitable) you could tap the single + output to feed into a dummy load of say 8 Ohms, and to your analogue input of the MCU, as long as you also connect the - amp ouput to an 8 Ohm dummy load. The problem is that the device you show is not really suitable for microphones. Instead what you're after is more like a microphone amplifier that will provide the required gain you need and possibly other features like AGC etc. A simple op-amp with suitable gain (say 40 dB) may work very well and its cheap but you may also consider more features than available with simple op-amps, such as with these devices. Other vendors will have similar dedicated analogue gain blocks for microphones all in one package ... Good luck !


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