This tone recognizer circuit that relies on R5 and C1 was found in the December 1994 issue of Electronics Now. The circuit operates on voltages from 6 to 12 V typically.
This fuzz distortion circuit was found in old RCA documentation. Equivalent transistors may be...
This circuit with transistors of the time was found in the magazine Radio Electroinics of June of...
Several versions of this circuit can be found on this website. This makes use of FETs that can...