Audio compressor for scanner

A friend asked me recently if I could come up with a circuit that he could use with his scanner to equalize the volume of the various stations he receives on his scanner. He was frustrated by the fact that if he turned up the volume to hear the "quiet" signals (narrow modulation, etc.), that he would then get blasted by the loud signals.



I came up with a fairly simple circuit. The input comes from the speaker-out of the scanner. The output of the circuit is a low-level, high-impedance output, designed to be put into an audio amplifier (since his plan was to use an audio distribution amplifier anyway).



I have two videos that describe the circuit. The first is on the bench, describing the schematic and demonstrating its operation using a signal generator. The second video shows the circuit in use with a scanner.



Here are the video links:



Circuit fun: Automatic audio leveling circuit | audio compressor | for scanning receiver - YouTube



Automatic Volume Level Control circuit demonstration | scanner - YouTube



I hope you find this useful.