This circuit is from a Radio Electronics from October 1970. The circuit uses transistors from that era and has a low impedance output. The resistance R1 depends on the impedance of the input signal.
This circuit was found in a Popular Electronics from the 90s. The circuit uses a ceramic capsule as...
This circuit for link or alarm was found in the Encyclopedia of Electronic Circuits Volume 5 of...
This 15 W power stage was found in Radio Electronics magazine from August 1959. The transistors are the...