The EN129 Thru Zero Oscillator is an all analogue triangle-core VCO specialising in frequency modulation. Analogue through-zero FM modulation produces a wide array of timbres particularly useful for bell like or percussive sounds. Through zero linear frequency modulation can be precisely dialled in thanks to a dedicated CV input attenuator and through zero offset control. Logarithmic FM is also available via it’s own dedicated input with attenuator and both FM inputs have an LED to indicate incoming voltages. Simultaneous analogue wave outputs include: Sine, Triangle, Sawtooth, Square and Pulse wave with Pulse Width Modulation. The PWM control goes to zero at either end of it’s range, which is very useful for creating rhythmic sounds with voltage control. Furthermore the PWM control doubles up as wave shape modulation for the Sawtooth wave – gradually altering the waveform until it shifts half a cycle. The EN129 features Coarse and Fine frequency controls as well as an LFO mode. LFO range is accessed via an LED pushbutton that also acts as the LFO speed indicator – the button will light up when the waveform moves through its positive cycle. A new addition of a Soft Sync Input allows the phase of the oscillator to be controlled by an external oscillator for an even greater range of timbres.

The EN129 is based on the pioneering work by Douglas Kraul and Bernie Hutchins. You can read the original Electronotes article from 1981 that the design is based upon here. Electronotes 129