I have tried to design a amplifier for an electret condeser microphone. It is basically just a common emitter NPN amplifier.
The problem is the frequency response of the real circuit. I get the expected full response on frequencies higher than roughly 10kHz (scratching, s-sounds, crumpling paper). Lower frequencies are practically non-existent. The response I actually expect is below:
The -3db point (marked) is at around 10 Hz.
What could be the cause? Is there some major design error in my amplifier? Is it possible the microphone response is at fault or my biasing is wrong?
My schematic is below: (V1, C1 and Q1 are all part of the microphone capsule)