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.
This simple circuit was obtained from Popular Electronics in December 1990. The magazine no longer...
Indicated by a 90s Popular Electronics, this circuit amplifies acoustic signals for analysis on an...
) This variable frequency oscillator was found in an old American documentation. Transistors allow more...