This circuit lets through the 300 Hz to 3kHz range that corresponds to the human voice. We found it in the Radio Electronics magazine of February 1990. The circuit uses both parts of the LM381.
This amplifier with two FETs in direct coupling (cascode) was found in a 90s Popular Electronics. The...
This circuit, which is present in other points of this website, was found in a 90s Hands On...
This microphone preamp found in a 1995 documentation offers stable microphone operation. The...