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Summary of Contents for Cosmotronic VPRTEX
- Page 2 VORTEX USER MANUAL by Simon De Rycke / BRiES Thank you for purchasing VORTEX by Cosmotronic. VORTEX is a versatile analog dual triangle core complex oscillator with a wide frequency range, a lot of timbral shaping options, useful normalizations, CV inputs for every parameter and attenuators to control the amounts of both internal and external modulation.
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Page 3: Table Of Contents
TABLE OF CONTENTS CONNECTING VORTEX ......................2 FRONT PANEL FEATURES ...................... 3 VCO 1 ..........................8 shape ..........................8 wavefolder ........................9 phase modulation ......................10 low pass filter ........................ 11 VCO 2 ..........................12 shape ........................... 12 ring modulation ......................13 wavefolder ........................ -
Page 4: Front Panel Features
FRONT PANEL FEATURES coarse tune coarse tune octave switch octave switch fine tune fine tune +/- 1.5 semitones +/- 1.5 semitones VCO1 main out VCO2 main out LOW PASS FILTER (VCO1) The slider controls the cut-off frequency of the low pass filter of VCO1. You can modulate this frequency using a signal patched into the LPF input jack (normalized to the SINE of VCO2). - Page 5 FRONT PANEL FEATURES amount sliders amount sliders attenuators attenuators SHAPE (VCO2) The slider controls the waveshaper of VCO2. With the slider at the bottom position the signal coming out of the right MAIN output jack is a DISTORTED SINE wave. In the middle position the MAIN output sends out a TRIANGLE shape and with the slider in the top position the wave is shaped into a SAW.
- Page 6 FRONT PANEL FEATURES main out 1 LED main out 2 LED FM index LED VCO1 TRIANGLE OUTPUT This output is affected by the waveshaper, sync and FM. VCO1 SINE OUTPUT This output is affected by the sync settings and FM. VCO1 SQUARE OUTPUT This output is affected by the sync settings and FM.
- Page 7 FRONT PANEL FEATURES sync section sync inputs v/oct link VCO1 v/oct in VCO2 v/oct in SYNC SECTION With the toggle switch in the center position SYNC is disabled. Flipping the toggle switch to the left syncs VCO1 to VCO2. Flipping the toggle switch to the right syncs VCO2 to VCO1. The little switches on either side of the toggle switch let you choose between hard sync (sometimes referred to as ‘reset’) in the up position and soft sync in the bottom position (sometimes referred to as ‘flip’).
- Page 8 FRONT PANEL FEATURES FM controls FM inputs FM CONTROLS The FM INDEX knob located in the center of the module controls the global amount of both through zero linear frequency modulation and exponential frequency modulation for VCO1 and VCO2. The left THRU ZERO knob controls the amount of TZFM of VCO1 (attenuated by the FM INDEX knob). The modulator for this TZFM is normalized to the SINE of VCO2.
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Page 9: Vco1
VCO1 VCO1 is a TRIANGLE core oscillator. The core output is internally shaped to a SQUARE (for syncing VCO2) and a SINE (for modulation of every parameter on VCO2). This shaping happens before the modulation (except for the FM) so the settings of the sliders don’t effect these waves. You can listen to the core by auditioning the TRIANGLE output (picture 4) when the SHAPE slider is in the most downward position. -
Page 10: Wavefolder
WAVEFOLDER The WAVEFOLDER in VORTEX is based on a design made in 1977 by Barrie Gilbert which was made popular in more recent years by Open Music Labs (used with permission, many thanks!). It works by smoothly inverting the polarity of the output with rising input voltages to create oscillations that can be used to shape a triangle or saw into a sinewave. -
Page 11: Phase Modulation
PHASE MODULATION The phase modulation in VORTEX is actually a part of the circuit that also takes care of the wavefolding and waveshaping. It’s capable of phase modulation by taking the SAW wave and adding a DC offset. It’s only true phase modulation when using the SAW from VCO1 shaped into a SINE wave*. For the other waves (SAW, TRAPEZOID and SINE) it is psuedo phase modulation. -
Page 12: Low Pass Filter
LOW PASS FILTER The non-resonant LOW PASS FILTER sections of both VCO1 and VCO2 are identical. The filters have a 12dB/Oct slope which means that for every octave below the cut-off frequency (set by the LOW PASS FILTER slider) the amplitude of the oscillator drops by 12dB. Setting the slider in the top position keeps the VCO unaffected by the filter and setting it to the down position completely attenuates the signal. -
Page 13: Vco2
VCO2 VCO2 is also a TRIANGLE core oscillator. The core output is internally shaped to a SQUARE (for syncing VCO1) and a SINE (for modulating the parameters on VCO1). This shaping happens before the modulation accessible on the front panel so the settings of the sliders don’t effect these (the FM bus does though). -
Page 14: Ring Modulation
RING MODULATION Ring modulation happens when there’s two bipolar signals that are multiplied in a four-quadrant multiplier. A four-quadrant multiplier could be referred to as a biplolar VCA. Where a regular two quadrant multiplier or VCA (picture 11) attenuates the bipolar input completely when the modulator is in the negative part of its range (resulting in amplitude modulation) a four-quadrant multiplier (picture 12) actually inverts the incoming signal when the ‘modulator’... -
Page 15: Wavefolder
WAVEFOLDER The WAVEFOLDER of VCO2 is a unique and completely original circuit. It folds and distorts the SINE, TRIANGLE, INVERSE SAW and everything in between creating subtle rounding of the waves at low settings and rich metallic overtones at more extreme settings (pictures 13, 14 and 15). The WAVEFOLDER slider controls the amount of wavefolding. -
Page 16: Sync
SYNC SYNC refers to syncing the phases of two oscillators together. By syncing a VCO (slave) to another one (master) the slave oscillator is forced to restart its cycle every time the master oscillator does. The reset or hard sync happens when there’s a clear rising edge on the master VCO (picture 19). There’s another type of sync called soft sync or flip that doesn’t reset the phase of the slave oscillator to the start, rather it causes the oscillator to switch from the falling edge to the rising edge (or vice versa) whenever there’s a rising edge on the master VCO (picture 20). -
Page 17: Sync Toggle Switch
SYNC TOGGLE SWITCH VORTEX uses normalized connections to make setting up a SYNC sound really easy and quick without the need to patch any cables. For this it uses the SQUARE waves that are derived from the TRIANGLE core oscillators, this way the SQUARE outputs are not influenced by the wavefolders, phase modulation, ring modulation, shape modulation and filters. -
Page 18: Frequency Modulation
FREQUENCY MODULATION VORTEX offers several ways to modulate the frequency of both VCO1 and VCO2. Not only do the V/Oct inputs accept bipolar signals, there’s a lot of additional sonic mayhem to be explored by using through zero linear FM and exponential FM, either with the internally normalized connections or with external modulation sources. -
Page 19: Exponential Fm
EXPONENTIAL FREQUENCY MODULATION The main difference between linear frequency modulation and exponential frequency modulation is how it reacts to incoming voltages. In exponential FM every volt you add to the FM input causes the frequency of the oscillator to be multiplied by a certain integer. V/Oct tracking is exponential in nature and every volt added will result in a pitch one octave higher or twice the original frequency. -
Page 20: Patch Examples
PATCH EXAMPLES WAVEFOLD MAKESHIFT VCA Sending a negative voltage into the wavefolder on either VCO results in silence. This feature can be used as a VCA. Slightly offsetting any envelope with a negative voltage and using this envelope to modulate the wavefolder is all you need to do to achieve this. Using the same envelope to modulate the LOW PASS FILTER creates a classic subtractive synthesis voice or a low pass gate emulation. - Page 21 EXOTIC SHAPES Patching any of the outputs back into any of the inputs is always a useful experiment. The first picture is an example where the SINE output of VCO1 is patched into the PHASE MOD input. The second picture is an example of self-patching the SQUARE output into the FOLD input.
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Page 22: Addendum
ADDENDUM VCO1 FLOWCHART VCO2 FLOWCHART FM BUS FLOWCHART VORTEX / Complex Oscillator...
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