We found this circuit with 5.3V zener in a Philips publication from the 60s. The op amp could be a modern equivalent.
This circuit was found in documentation two years 80. Transistors can be modern equivalents. Or...
This circuit, very critical due to the frequency at which it operates, was found in an American...
This stereo circuit with the 2002 integrated circuit. The power is 6 W per channel with 16 V of...