Described in the December 1969 Radio Electronics magazine, this circuit is intended to supply the previous circuit. The circuit is not isolated from the power grid.
Found in na 1970 EDN this circuit has a parallel regulation providing a symmetrical output of 15 V....
This configuration found in a 1976 publication can be elaborated with more modern operational...
This ultra-simple meter uses an output transformer and a small speaker as a microphone. The...