Elby Designs ED117 Wavolver II Waveshaper Module

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Perfect Circuit Audio (RSS)

"The ED117 produces a wide variety of evolving waveforms in response to an external control voltage.

Driven by a triangle wave, it can produce an output wave that continuously evolves from a triangle to an antisymmetric pulse waveshape. In addition, the section of the antisymmetric waveform that is at a zero-volt level can be replaced by an evolving series of successively folded triangular sections, somewhat in the spirit of the popular Serge Wave Multiplier.

The Wavolver II is a novel, versatile waveshaper that generates a special kind of double-pulse waveform along with an extra folded-wave section added between the pulses. It generates a wide range of timbres from a gentle sine or triangle wave to a very rich signal with multiple zero-crossings per cycle. The module can be driven by any continuously varying signal. For simplicity let's assume a tri wave at the input. The circuitry works by only passing the input signal when its amplitude (positive or negative) is above a threshold set by the pulse width control. When it's below the threshold the output signal is zero. The signal consists of steeple-shaped pulses that can be swept from narrow for high harmonic content to full width, which results in a triangle wave (pulse width and modulation controls). This represents a wider range of timbres than from the familiar rectangular pulse generators, which give a square waves at full width.

In addition to the double-pulse generator, the Wavolver II has circuitry to generate a series of evolving folded waves between the pulses. These are mixed into the output via the "fold mix" control. The folder output is available separately to allow individual processing of the double pulses and the folds.

The double-pulse signal consists of a positive pulse and a negative one, and the resulting signal has odd harmonics only. The capability to produce waves with strong, odd-only harmonics is practically never seen in classical vco/waveshaper designs. There is a wide area of timber space available here that has been largely ignored. Adding the folder output produces high-energy even harmonics in the signal's spectrum.

In the Wavolver II there are several ways to modify the basic waveforms discussed above. First, the amplitude of the second pulse can be continuously tuned from -5V (as shown above) to +5V (pulse 2 amplitude control). At full positive amplitude, the signal has two identical positive pulses, resulting in a signal at twice the frequency of the driving signal. Waves with the second harmonic stronger than the fundamental are musically useful, as some acoustic instruments (bowed strings) share this characteristic.

Another way to change the basic waveforms is to add a DC voltage offset to the input signal (input offset control and modulation). A positive offset makes the first pulse stronger and wider and at the same time it makes the second pulse weaker and narrower. Again this adds even harmonics into the output spectrum and results in some interesting timbres, especially when modulated.

Finally, the wave shape can be modulated by modulating the input waveform. There are many ways to do this, of course.

Features

Input Offset Modulation input with Depth and Level knob
Pulse Width Modulation input with Depth and Level knob
Bi-polar Pulse 2 Amplitude knob
Fold Mix knob
Input
Main Out
Folder Out"