This circuit was found in an English publication from 1967. The circuit is for listening on a phone. Transistors are types of germanium of the time.
This circuit that converts voltages from a battery into high voltages for tube circuits was found...
The assembly of this circuit was described in the January 1977 issue of Radio Electronics...
This preamplifier for high impedance microphone is designed to make a good addition to the speaked word...