Circuit for stereo width control and enlargement

With this stereo width control a continuous adjustment between mono over stereo to super stereo is possible. The latter setting can be acoustically meaningful if the two boxes are too close to each other in relation to the listening distance. The adjustment range is approx. -24% to 100% (= mono).

In order to achieve maximum headroom, an exact adaptation of the input-side base voltage divider can be useful. An exact adjustment can be made if the 68kΩ resistors on the far left of the schematic are replaced by 100kΩ spindle trimmers. About half the operating voltage should be present at the emitters of the output-side transistors. More accurate matching is possible with the sine wave signal of a test generator (for example, 1 kHz) and an oscilloscope, by feeding a signal at level limit and set with the two trimmers for the lowest possible distortion and symmetrical limitation. If these facilities are not available, the adjustation also performs well by ear. The photo shows the assembly of a reader. As you can see, he made a printed circuit board for the stereo width adjuster.