This circuit of a few watts of power shows a typical configuration from the 70s using driver and output transformers. Output transistors must use a heatsink.
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...