20Hz High-Pass Rumble Filter, Subsonic Blocker

This is a schematic diagram of 20-Hz high-pass rumble filter circuit.  Rumble noise could come from many sources, such as wind blow around an outdoor microphone, mechanical disturbance on phonograph, or many other possibilities. We can remove this noise by filtering the signal before the amplifier. The This circuit is designed for 20-Hz cutoff frequency and phonograph amplifier with gain 1-dB. Using large resistance value, this circuit is allowed to use lower-cost and smaller capacitors. This circuit assume that only audible part of the signal is important, so it will remove sub-sonic signals. Don’t use this circuit for recording which contain many for subsonic signals as part of the information such as  earthquake or meteor crash in movie’s sound. Here is the schematic diagram of the circuit: