This simple circuit needs a high gain stage to compensate for losses. It consists of a passive tone control obtained from Electronics Today International of the 90s.
In the figure we have the way to implement a 5 to 45 V zener diode with 50 mA of maximum current...
We found this circuit in a Radio Shack documentation from 1977. The circuit serves for a link of...
This circuit was found in the 1977 National Semiconductor FET Databook. The FET can be the BF245...