This NEC commercial amplifier was manufactured in Japan in the 1960s. The circuit uses 4 transistors from the time and was powered by a 9 V battery voltage formed by large batteries.
Obtained in an Argentine publication from 1973, this circuit sends the signal from a small record...
With this circuit it is possible to obtain a higher voltage from a zener diode. The circuit is from...
Found in a 90s Popular Electronics, this circuit can power a miniature railroad with voltages of 15...