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Features and Notes

Variable Slope VC Filter (VCFS)

The VARIABLE SLOPE VCF (VCFS) offers unique control of sound quality offered by no other synthesizer manufacturer. All VCF 's offer voltage control of the cut-off frequency, that is, control of which frequencies the filter lets pass. The VCFS allows the amount of filtering to be dynamically controlled as well, from barely perceptible filtering to highly resonant, sharp cut-offs. With the variable slope control in the center position, the VCFS acts as a typical flat-response VCF, with high, low. and band-pass outputs available simultaneously. The slope of the cut-off is 12 db/octave. As the control is moved toward the maximum position, the resonance of the filter increases, so that the cut-off becomes sharper. Although the VCFS will not ring like the VCFQ, it will resonate enough at the maximum setting to pick out harmonics from a complex signal input. As the control is moved to the minimum position, the cut-off slope will decrease to 6 db/octave. This type of chanqe of filter slope has been found to be an effective synthesis technique corresponding well with some of the transformations in acoustic instrument sounds. There are two signal inputs to the VCFS which can be mixed and manually cross faded from the associated knob.

Variable Bandwidth VC Filter (VCF2)

The VARIABLE BANDWIDTH FILTER (VCF2) has a band-pass output which can be varied manually or with voltage control. This is a standard response synthesizer VCF, typical to filters used in many studio systems. In the VCF2, two state-variable VCF's are connected in series to produce a total of five outputs. High pass, low pass, two fixed bandwidth outputs, and one variable bandwidth output are available. The outputs are all flat-response (no resonance) so the VCF2 is suitable for processing concrete sounds without introducing resonant coloration to the timbres. Under voltage or manual control, cut-off frequency of the high and low-pass outputs are affected, as well as the center frequency of the two band-pass outputs. Both center frequency and bandwidth are independently controllable on the variable bandwidth output.

Variable Q VCF (VCFQ)

The VARIABLE Q VCF (VCFQ) is an excellent general-purpose VCF offering simultaneous low-pass, high-pass, band-pass and notch (band-reject) outputs. The resonance (Q) of this filter is dynamically variable by manual or voltage control. The VCFQ has two signal inputs. One incorporates an automatic gain control to prevent the filter from overloading at high Q settings. The second input has a level control so that the percussive effects of overloading the filter can be exploited. When a pulse is applied to the Trigger input, the filter will ring, producing a damped waveform similar to that produced by striking a resonant object. The nature of this ringing is controlled by the Q and the filter frequency. Percussive effects ranging from clicks to the sound of wood blocks and bell tones can be produced and controlled. This ringing effect can be used in conjunction with signals applied to either of the audio inputs to achieve highly controlled complex tonal qualities.

Other comments:
A nice bit of flexibility is the "LO" setting that turns it into a CV processor! ... Recent updates to the filter's circuitry are noticeable as well - Its much easier to get tube-type harmonic warmth just by nudging the gain control. The feedback and overdrive characteristics have also been tweaked to be more musically useful... This filter will not oscillate unless you patch it up for feedback... Hi-Lo range switch for fantastic and unique audio/cv applications - hit it with a pulse, get an unbelievably slow damped sine wave. Calibrated 1 v/oct and attenuated cv inputs, just like the oscillators... Since it's a multimode filter, it's 12 dB/oct rolloff. You may want a LPF with more 'bite' in some applications. I think the bandpass and allpass sections of this filter have 6 dB/oct rolloff.

Wizardry: Must be patch-programmed to oscillate. Feed an output back into an input, then turn the Q up to get a nice sinewave. The various outputs will then be 90 degrees phase-shifted from one another.