Electronic Potentiometers

Potentiometers are, arguably, not the best way of controlling the volume and tone settings in an AF amplifier. We all know that they can cause scratching noises when operated, collect dust, and sometimes develop contact problems giving rise to troublesome discontinuities in the operative range. High qual- ity potentiometers for AF appli- cations are not only difficult to obtain, but also notoriously ex- pensive. In the following sec- tions we will briefly examine a number of low-cost alternatives to potentiometers used in various circuit sections of AF equipment. The carbon track potentiometer This most commonly used voltage divider is generally composed of a carbon film deposit on a ceramic base ar- ranged in a three-quarter cir- cular form (270°). The poor contact definition of the wiper on this thin carbon film readily gives rise to scratching noises made audible in the loud- speakers. Furthermore, dust and foreign particles can easily enter the potentiometer enclos- ure, and ...