This circuit was found in an old American publication. The integrated circuit used is no longer easy to find, but if found it can be used in excellent tone control. Common operational amplifiers can be tried. Like the 741. The source must be symmetrical with excellent filtering and the signal cables must be shielded. The circuit is connected to the input of an amplifier. The potentiometers used must be linear. This circuit corresponds to one of the channels of a stereo system, and another unit must be mounted for the right channel.
