This circuit is from a documentation from the 70s. The circuit uses logic gates of the time, which in many cases were arrays of transistors allowing use as audio amplifiers, as in this case.
This stage was used in old audio ampliiers and radios from the 1950s and 1960s. It uses one of the...
Found in a 90s R-E Experimenter Handbook, this amplifier uses an integrated circuit from that...
We find this circuit in an American 1980s documentation. The unijunction transistor may be the...