LM387 dynamic microphone preamplifier circuit
A dynamic microphone preamplifier circuit can be made using LM387 dual operational amplifier integrated circuit. Input impedance corresponds to 47k, it depends almost exclusively by R1. If you wish to connect a dynamic microphone with a different value, the resistance R1 can be changed. Dynamic microphone preamplifier amplification was set at 40dB. Input impedance of the amplifier where it will connect the preamplifier must be at least 100k.
Report Signal / noise depends on the passive components used. At an input voltage of 10mV, the signal / noise greater than 80dB.