Volume synchronization circuit constructed with discrete components

Many audio systems use a single potentiometer to adjust the volume of L and R channels synchronously, which is often achieved using a dedicated integrated circuit (such as LM1035), and some also use a coaxial potentiometer to adjust. Here we introduce a simplest synchronization circuit made of discrete components, which is very practical for occasions such as temporary replacement and amateur production, and will not feel noise.

The circuit is shown in the figure below. The resistance of field effect tubes Q1 and Q2 changes with the gate voltage. When the RP sliding arm moves upward, the gate potential increases, and the resistance between the source and drain decreases; when the RP sliding arm moves downward, the potential decreases and the resistance increases, thereby attenuating the input signal to varying degrees to achieve the purpose of volume adjustment. Similarly, for more channels, just connect a few more field effect tubes (as shown in the dotted box). The oCI has a buffering effect on the adjustment, making the adjustment feel soft.