This low-power benchtop circuit has an output for external use and other features. The circuit is from the 1995 Encyclopedia of Electronic Circuits Volume 5.
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...