A dynamic microphone preamplifier can be realized 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. In
put impedance of the amplifier where it will connect the preamplifier must be at least 100k.