The Twinpeaks' distinctiveness is the way how the two-peaked bandpass is created. Not, as so often, by combining a lowpass and a high pass filter but by a inverse-parallel interconnection of two low pass filters. What's the benefit? Well, on one hand it's possible to morph the filter characteristic from lowpass to bandpass with the CURVE control and on the other hand it doesn't matter which filter is tuned lower than the other - usually this would result in unwanted cancellations but here this doesn't happen and a pass band always exists. When the filters are tuned almost unisono you can create very narrow passbands with almost no bandwith.
Very unique is the Twinpeaks' resonance circuitry which has been designed to tilt momentarily into self-oscillation when pulsed waveforms (gates, triggers or one-shots) are used as audio inputs. This results in warm and percussive "pings" which have a longer duration at low frequencies, e.g.; when either peak is tuned to approximately 40Hz cutoff, they will sustain for 4 to 5 seconds. The RES/PING control sets the damping. The resonance is set for both filters simultaneously and can be voltage controlled.
The cutoff frequencies are tuned individually with the PEAK A and PEAK B controls and can be modulated with voltages, too. The inputs have polarizers (Peak A Mod and Peak B Mod) for scaling. wit hthe help of the DUAL MOD parameter it's possible to tune both cutoffs simultaneously which is ideal to preserve intervals between the cutofffs. The Dual Mod's tracking is around 0.5V/octave when the attenuator is fully opened.
There's also a 1V/octave input which allows for playing the filter tonally over five octaves.
The Twinpeak offers two audio inputs. Depending if one or both are used the potentiomenter LVL/IN FADE functions as a level control or a crossfder between the two inputs. It can get very interesting when you feed the Twinpeaks with both audio signals and slow pulses as this will excite the resonance in different ways.
The MK2 version features a higher output amplitude, a wider resonance control range and normalized CV inputs.
2 audio inputs, filter output
CV inputs: 1V/oct, Dual Mod, Mod Peak A, Mod Peak B, Resonance
3U Eurorack module, 12HP wide, 22mm deep
power consumption: ~ 35mA @ +12V and 35mA @ -12V