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I have this headset I'd like to use on a device that has a line in input. I've found this nice example circuit: Electret Microphone Pre-amp

A lot of the calculation remains to be done though, depending on the microphone characteristics. But I don't have them.

May I measure them? Or would anyone know what an Android mic in typically expects/looks like (I'm talking about the TRRS jack). It may not be Android, this microphone seems to work on any "PC sound card MIC in", so if someone had a link to that, that'd be great too!

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  • \$\begingroup\$ so if someone had a link to that, that'd be great too! ... link to what? \$\endgroup\$ Commented Apr 6 at 6:45
  • \$\begingroup\$ @jsotola I am guessing a link to Android headset specs. It's amazing that we can just google it these days. \$\endgroup\$ Commented Apr 6 at 7:11

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The mic and the electrical interface for it are just fairly typical for generic electret mics.

The specs are rather loose but the Android ecosystem has defined a specification to which all headsets and all devices that call themselves Android must adhere to, which defines things line pinout, bias voltages, input and output impedances and signal levels under given conditions of testing.

The headset specs are here: https://source.android.com/docs/core/interaction/accessories/headset/plug-headset-spec

The device side specs are here: https://source.android.com/docs/core/interaction/accessories/headset/jack-headset-spec

Basically, you need a mic preamp circuit which powers the mic and amplifies the audo, then you likely need to adjust for the input voltage so either make the preamp gain adjustable or make a fixed gain with adjustable output level depending on what's easiest for your given setup of voltage supplies and circuit complexity.

Typically the mic is biased with 2.2 kohm resistor to 2.2 volts. AC couple the audio with large enough capacitor based on your input impedance to allow passing low enough audio frequencies you want.

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