This small tube amplifier appeared in Radio Electronics magazine in February 1958. The circuit is powered by the mains with a power transformer and output with different impedances.
Using a 12 V transformer, this unit can provide a much higher output voltage. The circuit is from a 90’s...
Found in Linear Technology documentation from the 1980s, this circuit has an accuracy of 0.01%....
This circuit was found in a 1967 EEE. The transistors are from the time and can be tested...