This old 1967 audio preamp uses germanium transistors. It was found in Japanese documentation at the time and has a gain of 70 dB, being powered by p V. The input sensitivity is only 12 mV.
This General Electric circuit was published in 1970. The LED is infrared and the voltage according...
This circuit was found in the October 1989 issue of Radio Electronics magazine. It drives an...
The transistor can be a modern equivalent and the transformer is the type of output found on an...