I like to known the signal level of headphone MIC that we use in recording in computer or any other recording devices. And what is the voltage that required to powering MIC of headphone(common type of headphone).
Common headsets use an electret mic that is powered from 3V to 10V through a 2.2k to 10k resistor. The output is 5mV to 10mV RMS when speaking normally 10cm away.
The preamp should have an input resistance of 10k to 100k ohms.