XR22 VCO FT Frequency Shift Keying Oscillator

CG Products XR22 VCO FT

The XR22 VCO FT from CG Products is a VCO with bipolar amplitude modulation and a unique Frequency Shift Keying circuit. The module operates in three frequency ranges selectable by switch, lo, mid, and hi. The XR22 includes a pair of frequency controls, labeled F1 and F2. F1 and F2 each span an eight-octave range. A common tuning switch selects whether the frequencies are independent or if F2 operates at a ratio of F1. The FSK switch selects between three modes, F1 where the left side controls the frequency, F2, which puts frequency control on the right half of the module, and a third mode indicated by a square wave. In this mode, the XR22's square wave controls the Frequency Shift Keying circuit. The FSK circuit switches which half of the oscillator controls the frequency. In this mode, adjusting the F1 or F2 both affect the frequency and waveshape of the output. F1 controls the positive pulse width and falling portion of the ramp wave, while F2 sets the rising portion of the ramp wave and the pulse width of the lower half of the pulse wave. Using the internal square wave in this mode allows for more predictable behavior and waveshaping, particularly when F2 operates at a ratio of F1. However, using external unsynchronized oscillators may result in unexpected behavior. Using square wave LFOs or clocks provides a great way to quickly swap between frequency ranges in time with other elements of your patches such as sequencers, envelopes, or random voltages.

The AM or amplitude modulation section includes both manual gain knob and CV input. The bypass control blends from the signal present at the AM input on the far left side to the internal sine/triangle output. While bipolar Amplitude Modulation is typically associated with audio rate signals and ring modulation, it also acts as an internal VCA for envelopes, LFOs, or any other signal. Patch either oscillator shape output to the amplitude modulation input for patch programmable wave shaping. Patching the sine/triangle output back into the AM input bends the output to curve away from linear oscillations. Patching the square/pulse output adds a hard edge to the output, morphing from triangle/sine to a sawtooth or rectified sawtooth, adding a great deal of harmonic content. F2 includes an input that either acts as a secondary 1V/oct input or as a hard sync input to automatically reset the waveform. The XR22 VCO FT's Frequency Shift Keying circuitry provides a dynamic way to both swap frequency content and add unique waveshaping and sequencing possibilities, particularly when used in conjunction with the bipolar amplitude modulation.

XR22 VCO FT Features

• VCO with bipolar amplitude modulation and frequency shift keying
• Includes a pair of switchable frequency controls with manual, external, and internal control
• Four-quadrant multiplication circuit great for ring modulation
• Pulse/square and triangle/sine outputs
• Frequency controls act either independently or at a ratio