DSP Functions
Non-linear Functions
14-46
Lowpass Filter with Clipping (LPCLIP)
This is a one-pole Þlter, which is programmed just like LOPASS. The difference with LPCLIP is
that the amplitude of the input signal is multiplied by 4 before the Þlter. This can cause the
signal to clip, which can produce interesting results. Naturally, youÕd use this function only
when you want to induce clipping intentionally as a component of your sound.
Pulse Width Modulation (PWM)
Pulse width modulation can produce some classic synth sounds, and can break new sonic
ground as well. Its operation is very simple; it adds an oscillating DC offset to the input signal
(shifts it toward positive or negative full scale). Unless it causes the signal to clip, it wonÕt have
much effect on the signal. ItÕs designed to be followed by DIST, with the Adjust parameter for
DIST set to a fairly high level. The DIST function will drive all positive elements of the signal
toward positive full scale, and negative elements toward negative full scale. The result is a
rectangular wave with a width that varies according to the Adjust level of PWM.
PWM wonÕt affect a square wave input. Sine and triangle waves will produce familiar PWM
sounds. More complicated waveforms will result in discontinuous rectangular waveforms.
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0 50 100 150 200 250 300 350 400 450 500
Time in milliseconds
SINE followed
by PWM
PWM Adjust
from 30 to 70
Signal level
70
30
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0 50 100 150 200 250 300 350 400 450 500
Signal level
Time in milliseconds
SINE ->
PWM->
DIST
DIST gain = 0;
PWM Adjust
from 30 to 70
70
30
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