Found in an English publication from the 1980s, this circuit can be built with equivalent transistors such as the BC549. The signal must be applied to an external amplifier.
The transformer of this unit found in an old Japanese documentation can have 22 to 25 V of...
This JFET amplification stage was found in the April 1993 issue of Electronics Now. The input...
This circuit with two power transistors was found in Radio Electronics magazine from October 1960....