In addition to tone control, this circuit of the SGS 1982 linear integrated circuit manual has a loudness control. The supply must be made with a 24V voltage source.
This circuit was found in the January 1995 Electronics Now magazine. Its configuration is valid for...
This circuit with transistors in parallel was found in a Radio Electronics of August 1952....
We find this simple circuit in an English publication called Electronic Circuit Design no. 3 of...