Found in 1968 Mullard documentation, this circuit uses period components. The transistors are matched pairs and the sensor is an Indian photocell of the time.
Found in old documentation, this circuit applies to almost any common operational amplifier or...
This circuit is used with low impedance microphones, such as small speakers, magnetic capsules of...
This filter can be used to eliminate hum in sound equipment. Operational amplifiers can be 741 and...