Cosmotronic VPRTEX, Руководство пользователя

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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. Adding 2V
will cause the pitch to go up 2 octaves (four times the original frequency).
Using exponential FM provides a wide range of timbres when using a VCO as a modulator. It’s also
ideal for patching in an LFO as a modulator to create a gentle (or extreme) vibrato.
Both VCO1 and VCO2 have a knob labeled EXPONENTIAL for setting the maximum amount of
exponential FM. The knob labeled FM INDEX controls the global amount of frequency modulation (this
setting also applies to the linear FM of both VCO 1 and VCO 2). The modulator for VCO1 is normalized
to the SINE from VCO2 and vice versa. It is possible to use a different signal as a modulator by
patching any VCO into the input jacks labeled EXPO. These inputs accept bipolar signals and accept
both DC (static or slow moving CV) signals and AC (fast alternating CV) signals.
It’s possible to get a decent (but not perfect) pitch tracking on the EXPO inputs by maxing out the FM
INDEX knob and settings the EXPONENTIAL knob to approximately 3 o’clock. This can be used to act
as a ‘quick and dirty’ way to transpose any pitch sequence patched into the regular V/Oct inputs.
FM INDEX
The big knob in the center of VORTEX controls the global amount of FM for VCO1 and VCO2 for both
linear and exponential frequency modulation. Turning it to the right increases the amounts of FM and
this is indicated by the LED light surrounding the knob shifting from blue to orange.
It’s possible to modulate the global amount of FM by connecting a signal to the FM INDEX inputs.
These inputs accept bipolar signals. The left FM INDEX input is normalized to the right one (indicated
by the arrow) so when a modulator is connected to the FM INDEX input of VCO1 this will also modulate
the FM INDEX of the right VCO. Of course it’s also possible to connect different modulators to either
input. The FM INDEX knob acts as an offset for both inputs (meaning that any signal you send into the
inputs will be added or subtracted from the DC voltage generated by the position of the knob which
opens the VCA for the FM bus).
TUNING TRIMPOT
If you remove VORTEX from your rack you’ll notice two little trimmers. These are trimpots for
changing the root frequency of VCO1 and VCO2 seperately.
You could for example tune VORTEX to C0 (with the
COARSE knobs completely CCW) to be able to
return to a stable pitch quickly whenever you knock
either VCO out of tune by accident. This could be
useful when performing for an audience or in any
kind of live situation.
Take care when adjusting this trimpot. Stop turning
it immediately when there’s a ‘clicking’ sound.
VORTEX / Complex Oscillator 18