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. By amplitude modulating the input voltage of this
circuit the number of inversions increases and quadruple wavefolding of the output signal is achieved.
The slider of the WAVEFOLDER increases the amount of folds applied to VCO1. At subtle settings
(together with some slight filtering) you can use it to shape the SAW into a SINE (more info on this is
in the next section about phase modulation). The range of the slider is 0V to 5V of offset.
It’s possible to modulate this parameter with the SINE from VCO2 (normalized). The knob is an
attenuator for this modulation. You can override this normalization by patching a signal into the FOLD
input. This input accepts bipolar signals and the knob is an attenuator for this external modulation.
Maximum modulation is achieved (with the slider completely down) from 0V to 5V. Sending in a
negative voltage (with the slider still in the down position) will attenuate the wave completely. This
also happens when using the internal modulation when the voltage of the SINE of VCO2 is negative
(i.e. during the negative part of the oscillations of the SINE of VCO2). This feature can be (mis)used
as a make-shift VCA for VCO1. When no sound is present at the MAIN output the LED under the coarse
tuning knob is dimmed completely.
It is possible to achieve higher amounts of wavefolding by sending in higher voltages. Keep in mind
that the total amount of wavefolding is controlled by the sum of the DC offset generated by the slider
(0V to 5V) and the internal or external modulation (picture 6).
VORTEX / Complex Oscillator
9
W
A
V
E
FO
L
D
E
R
0V
5V
M
O
D
U
L
A
T
I
O
N
SINE VCO2
+/- 5V
2.5V
picture 6: modulation ranges
time
0V
5V
2.5V
7.5V
- 2.5V
WAVEFOLDER DC OFFSET
total amount
