The Dual Four Pole is a dual filter based on the discrete transistor filter made for the Buchla 1960 System in the 100s. The left side of the moduleHigh pass filter, Right sideLow pass filterIt has become. Each filter has a cutoff knob, a resonance knob (not self-oscillating), two cutoff CV and resonance CV inputs, and an audio input / output. The output of the high pass filter isInternally connected to the input of the low pass filterTherefore, it is possible to pass the input signal through two filters. When using the output of the high-pass filter, the internal connection is disconnected and it can be used as two independent filters.