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 amplifier was found in a 1957 Rayrtheon documentation. The circuit can be fitted with a BC558...
This circuit was obtained from the May 1971 issue of Radio Electronics magazine and is intended for...
Although it is a common configuration today, this circuit was taken from an old publication. The...