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This is a 4x4 active matrix mixer. Each channel features two inputs and two outputs, with the outputs utilizing an inverting amplifier circuit. It operates on a single 9V power supply. To introduce complexity into the feedback loop, the bias of each output can be adjusted using a pot. The output coupling capacitors are switchable between 10µF and 0.1µF. Combined with an output pot, this effectively forms an adjustable high-pass filter.