This primitive solar radio was found in a Gernsback publication from 1960. The transistor is made of germanium of the time and the earphone is magnetic with high impedance.
This circuit was found in an Electronic World of 1968. The circuit uses power transistors of the...
This circuit is from Radio Electronics from March 1985. The circuit uses common components at the...
This simple TTL digital amplifier uses NAND gates and a high impedance speaker. ...