Description A difficult problem in the design of conventional stereo tone controls is obtaining synchronous travel of the potentiometers. Even a slight error in synchrony can cause phase and amplitude differences between the two channels. Moreover, linear potentiometers are often used in such controls, and these give rise to unequal performance by human hearing. Special potentiometers that counter these difficulties are normally hard to obtain in retail shops. A good alternative is a control based on a rotary switch and a discrete potential divider. The problem with this that for good tone control more than six steps are needed, and switches for this are also not readily available. Fortunately, electronic circuits can remove these difficulties. Circuit Diagram: The analogue selectors used may be driven by mechanical switches, standard logic circuit or a microcontroller. The selectors used in the present circuit are Type SSM2404 versions from Analogue Devices, which switch noisele...