This circuit for audio signals was found in the March 1990 Radio Electronics magazine. The circuit uses a unusual optocoupler that can be replaced with an equivalent one.
This circuit appears in other articles and suggestions for circuits in this section from other...
This tone control was obtained in a Signetics documentation of the 90s. The integrated circuit can be...
We found this circuit in an American publication from the 1990s. Any FET can be used. The circuit...