design a microphone preamplifier for a publuc address amplification system. The output signal from a magnetic voice coilmiscrophone typically has an output resistance of 100 ohms and apeak value of about 10mV under normal speaking conditions. Yourcircuit should amplify the microphone signal to a 1-V level forinput to the systems power amplifier and should include a volumecontrol to adjust the microphone signal over the complete rangefrom zero to maximum. To help reduce the coupling of 60 Hz noisesignals from power wiring into the microphone, the input resistanceof the amplifier should match the output resistance of themicrophone. Note that including a variable resistor orpotentiometer on the input side of the circuit is not a good ideabecause any electrical noise generated by the wiper arm will beamplified by the preamplifier circuit and fed in amplified form tothe power amplifier.