Frequency Shifter / Thru-Zero VCO

Frequency Shifter combined with Thru-Zero Quadrature VCO

This frequency shifter utilizes a so called Dome filter to perform sine / cosine transformations combined with two precision multipliers for a sine / cosine signal. It includes a mixer for two audio signals, balance pot from ring-modulation to single side-band suppression (=frequency shifting). To obtain this sine / cosine carrier signal a Doepfer A110-4 is incorporated.

The RMO knob allows a continuous shift between ring-modulation (only one multiplier) to single side band suppression (SSB). You can create interesting sounds in between and enables you to tune the exact SSB balance for your signal. The input mixer allows you to insert a digital delay for delayed shifts. Simply use a patch cord from the second out to the input to get a special kind of phasing. It is a variation of so called „Barber pole“ phasing.

For up or down shifts the phase of the carrier signal must be inverted. Doepfer’s A110-4 produces a sine / cosine signal that shifts phase with the LFrq pot. Modulation for LinFrq and XFM for extraordinary shift sounds become thus possible. The A110-4 was intended to apply in frequency shifting systems. Here the VCO is changed towards more LFO mode using a 1nF capacitator (see the description on Doepfer site).

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