Operation Manual

2.1 Tutorial 1. A Simple Analog Synth 25
Figure 10: Tutorial 1, step 3
and you will hear the sound become brighter as the cutoff frequency increases (to hear the effect
you can use any waveform from the VCO except the sine wave, which only has one frequency
component). When this knob is turned completely to the left there is no sound (since the cutoff
frequency becomes so low that all the components are filtered out from the sound). When the knob
is fully turned to the right, the full spectrum of sound is heard.
The resonance knob is used to enhance the frequency components near the cutoff frequency. If
you turn this knob to the right and then slowly tweak the frequency knob, you will hear the different
frequency components of the sound come out as the cutoff frequency is equal to these frequencies.
Try changing waveforms and playing with the frequency knob to hear the differences in harmonic
content between all waveforms. If, when working with a sine wave, you adjust the cutoff frequency
close to the signal frequency and then increase the filter resonance, the filter will act more like an
amplifier than a filter. Interesting effects are achieved as the resonance rises and the filter starts
to self-oscillate and the sound to saturate. Filters can be effectively used with the noise waveform
because of all the harmonics they contain (try it with a lot of resonance).
Note
Modules can be deleted in the construction area the same way as the wires can be. Click on a
module to select it and then use the Del or BkSp (delete key on Mac) key on your computer
keyboard.
Step 4: Modulating the filter
Description
As was the case with the VCO, the Vlowpass2 filter has a modulation input that can be used to
modulate the cutoff frequency of the filter.
Construction
• Pull a wire from the output of the LFO that we already have in the construction area to the
second input of the Vlowpass2 filter.