ACL - Discrete Core Ladder VCF

Advanced low-pass design – The Discrete Core Ladder VCF shines with crisp sound, a very low noise-floor and a multitude of technical gimmicks. The module features a three-channel input mixer with saturation capabilities. Four outputs provide audio material filtered with -6 dB, -12 dB, -18 dB and -24 dB edge steepness. Each connector is phase-shifted by 90 degrees compared to the prior socket. Cutoff and resonance are voltage controllable. While self-oscillating, the filter can be played chromatically. This means, that the Discrete Core Ladder VCF is usable as a quadrature VCO as well. Thanks to a boost knob, the bass fundament can be kept intact at high resonance settings. A high-pass filter in the feedback path allows users to alter the resonance behavior. Compared to Moog’s classic Ladder design, the sound of the ACL circuit is considerably rougher. Saturation effects lead to roaring results. Tip: Be sure to try out filter FM patches!

The Discrete Core Ladder VCF comes equipped with three signal inputs plus dedicated volume controls. Levels above 8 Vpp result in saturation effects. The filter itself features cutoff and resonance potentiometers. In addition, there are three CV inputs plus attenuators. Two channels influence the cutoff frequency. The third control voltage input is wired with the resonance parameter. Furthermore, there is a 1v / octave connector. While self-oscillating, the circuit can be played chromatically over a range of five octaves. The resonance behavior is adjustable via a three-way switch. More precisely, the control element can be used to set the cutoff frequency of a high-pass filter, which is situated in the module’s feedback path. As usual with Ladder designs, high resonance values lead to an attenuation of the bass frequency range. To compensate this characteristic trait, the Discrete Core Ladder VCF was equipped with a boost knob. Filtered audio material is emitted via four outputs with different slopes and phases, in detail:

• -6 dB edge steepness per octave, no phase shift
• -12 dB edge steepness per octave, 90 degrees phase shift
• -18 dB edge steepness per octave, 180 degrees phase shift
• -24 dB edge steepness per octave, 270 degrees phase shift