Filter 8

An analogue voltage controlled filter in 12 HP built on the classic OTA-style four-pole cascaded lowpass, with a separate output for each of its four lowpass stages, each with its own character. Pole mixing adds a one-pole highpass, a band boost and notch response, a phase shifter and a four-pole bandpass, all available at the same time, with an LED at every output. Its resonant feedback circuit keeps the low end as resonance rises, and at higher settings the filter self-oscillates into an eight-phase sine wave VCO with switchable gain compensation, low distortion, constant amplitude and accurate tracking over at least five octaves; switched to low frequency, it becomes an eight-output slew modifier or an eight-phase LFO. Exponential and linear FM work at the same time, the linear input with an AC switch, and a hold input and switch freeze the outputs by hand or under gate control, halting a modulation or giving a sync-like effect at audio rates. A dedicated ping input turns it into a percussion voice.