This amplifier with old germanium transistors is from a 1957 documentation. The power is a few hundred milliwatts and the transformers are common types of driver and output of the time.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...