This circuit is from a 1975 RCA tube manual. It appears elsewhere on the site. R5 depends on the voltage of the amplifier with which it is used and can be changed.
Using LM3909 integrated circuits, this circuit was found in an American documentation from the...
This circuit was found in an ancient American documentation. The components of the time are not...
This circuit with low impedance output and 900k input impedance was found in the October 1993...