ABSTRACT
The job of a balance control on a preamplifier is to adjust the relative gain of the left and right channels, and so alter the position of the stereo image to the left or right, and do nothing else at all. Since the balance control is usually a set-and-forget function that does not require readjustment unless the listening room is rearranged, it is not often considered when controls are being motorised. In fact, getting the balance exactly right by leaping up and down between sofa and preamplifier is rather more tiresome than manual adjustment of volume. Some preamplifier designs have attempted to evade the whole balance control problem by having separate but concentric volume knobs for left and right channels. An active balance control is configured so that it makes a small adjustment to the gain of each channel rather than introducing attenuation, so that any noise/headroom compromise can be avoided altogether.
