This circuit has more power than the previous one, since it includes a powerful transistorized stage. The circuit is from Radio Electronics from July 1985. It includes the power supply.
This is a Japanese commercial circuit found in a 1967 documentation. The transistors are from the...
This circuit was found in a Radio Electronics from October 1952. The circuit equalizes the sounds...
This circuit is from an old American publication, but it can be easily implemented with modern...