A microphone preamp is a preamplifier used to amplify a microphone's low output voltage to a stronger, more usable level. A microphone preamp must provide stable gain for small signals without being sensitive to induced noise from cabling and without distorting large amplitude signals. Most microphones must be used in conjunction with a microphone preamp to function properly.
Simple audio Pre-Amp mic
This circuits use infront an RF oscilator to make an RF transmitter that is very sensitive to sound