This variable 1 A power supply with voltages up to 30 V was found in an article in June 1986 Radio Electronics magazine. The 723 IC is well known to magazine readers of the time and even today.
This is a Japanese commercial circuit found in a 1967 documentation. The transistors are from the...
This circuit was found in a Radio Electronics from October 1952. The circuit equalizes the sounds...
This circuit is from an old American publication, but it can be easily implemented with modern...