By J.R. Laughlin
This circuit, created by J.R. Laughlin and published by audioXpress in October 2008, contains an audio amplifier capable of driving a speaker with circuitry that automatically maintains the same relative maximum output regardless of extreme levels that are occurring at the input. It does not “compress” the peaks, but simply “turns down the volume” as you would do with your volume control.
This maintains a steady output volume for very widely varying input levels. Extremely low distortion results from the use of a self-adjusting, purely resistive voltage divider circuit to perform this action, an LDR (light dependent resistor), instead of a semiconductor device.
As the author explains, “I originally designed the circuit to be used with an old audio oscillator whose output level varied considerably with changes in frequency. It cured that problem beautifully. I also have applied it to the following:
- regulating TV sound level (loud advertisements!)
- my front door intercom
- CB radio and amateur radio sound regulation
- a public address system
- music systems"
You can read the complete article here.
