Available as an assembled Module and as a DIY project.
This Module is currently available.
Sine wave LFO with four outputs phase shifted by increment of 90°
The quadrature LFO is a special module that was not found on many modular synthesizers back in 1970s. Mostly, only companies like Polyfusion, Buchla or Serge would propose such a unique LFO.
Basically, it is a sine wave LFO with four outputs. The outputs run at the same frequency but are phase shifted by increment of 90°. That is, the first output has a shift of 0°, the second 90°, the third 180° and the fourth 270°.
The module is designed for modulating up to four sources at the same rate but out of phase. This makes it possible to achieve so called "Barber pole" effects or "Shepard tones". For example, imagine that you connect each output of the Quad-LFO to the 1V/Oct input of four different VCOs. Then you'll hear continuous though steady rising and falling of intermangled pitches (see also Tritone paradox). It can be used also to drive four VC-panners to create rotating sound effects that fill the stereo space.
The core of the circuit is based on the quadrature oscillator circuit of Ian Fritz's ChaQuO chaos oscillator. It is modified to have voltage control of the frequency. The outputs have added buffers with LED indicators and a toggle switch that makes it possible to exchange the phase of the 90° and 270° signals in order to change the direction of the phase rotation. This simple trick is very handy when performing "barber pole" modulations.
Each LED shows the positive part of the corresponding signal. They are organized on a circle to visualize the phase differences between the signals.
These merchants probably sell this module. Huh?
