Here is simple preamp mic. This circuits use infront an RF oscilator to make an RF transmitter that is very sensitive to sound. A microphone preamp must provide stable gain for small signals without being sensitive to induced noise from cabling and without distorting large amplitude signals. A microphone preamp is a amplifier used to amplify a microphone’s low output voltage to a stronger, more usable level. Most microphones must be used in conjunction with a microphone preamp to function properly.
Here is a schematic simple PreAmp mic drawing:
simple preamp mic