This circuit with a bargraph scale was found in a 90s Popular Electronics. The circuit measures the intensity of a sound in three scales. R14 works as a sensitivity adjustment.
This circuit was obtained from an old documentation, but as it uses still current components it can be...
This audio circuit has an output power of 1 W. We found it in the Radio Electronics magazine of...
This circuit that uses only discrete components (transistors) mimics the sound of an American...