This circuit from General Electric was found in a 1967 documentation. The SCR is of the time, as are the transistors, but equivalents can be used.
This amplifier for sound equipment was found in the Philips Databook of 1990. The circuit can be...
I found this circuit in an English publication from 1989. This configuration can be mounted with...
The circuit shown is from a 1978 Texas Instruments optoelectronics manual. The circuit can use...