Preamplifier stage (CB8934E)

This circuit is from a 90s Popular Electronics. It appears elsewhere on this site. Q1 can be any general purpose transistor.

High gain audio amplifier (CB8938E)
This high-gain circuit was found in an American publication from the 1990s. The circuit can use...
Automatic Lighting Control (CB17427E)
This circuit automatically controls the degree of illumination. As the circuit is from 2001, it...
Graphic equalizer KA2223 (CB25943E)
This circuit was found in a Radio Electronics from April 1990. The circuit has 5 equalization...