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 audio step operates directly with the 110 V mains voltage rectified and reduced. The output...
The MC1436 can also be used on this circuit found in Motorola's 1993 Linear Interface ICs. The...
The FET admits equivalents like the BF245 in this circuit that we find in a documentation from the...