13
OSCILLATORS
OVERVIEW
Oscillator 1 and oscillator 2 are the Sub Phatty’s primary
sound sources. They generate four basic waveforms:
triangle, sawtooth, square, and pulse.
The triangle wave consists of odd-numbered harmonics
only. Its fundamental is very strong, and its overtones are
very weak, making it less harmonically complex than other
waveforms. By mixing a triangle from one oscillator with
a more complex wave from the other, you can emphasize
one particular harmonic without mucking things up with
unwanted overtones.
An unfiltered sawtooth wave is much brighter, because
it contains all the natural harmonics. As the harmonics
ascend in frequency, they grow weaker in amplitude.
Sawtooth waves are useful for synthesizing bass,
simulating brass instruments, and more.
Although a pulse wave contains only odd-numbered
harmonics, it offers the most flexibility because you can
change the balance of those odd-numbered harmonics by
changing its shape. Think of a pulse-wave oscillator as a
switch you can turn off and on hundreds or thousands of
times per second. In a single pulse wave, the “switch” is
either on or off. Its pulse width is the proportion of the wave that’s on, usually expressed as a
percentage. A square wave is simply a pulse wave with 50% pulse width, meaning that in a single cycle,
it is on half the time and off half the time. If its frequency is 440Hz, that means it goes on and off 440
times every second, and the result you hear is the pitch A above middle C. Every pulse width has its
own characteristic sound, because each has a unique harmonic structure, making a variety of basic
timbres possible.
Unlike most synths, which simply switch between basic waveforms, the Sub Phatty allows you
to gradually change the oscillator’s output from one waveform to another, so it can generate
something partway between a sawtooth and a square wave, for example. We refer to such controls as
continuously variable
because there are no discrete steps between settings.
In normal operation, either the keyboard or external MIDI data controls oscillator pitch. You can also
apply the LFO or the filter envelope to modulate oscillator pitch and waveform.
OSCILLATOR CONTROLS
OCTAVE:
Use this knob to control either oscillator’s pitch range. Pitch range is expressed in feet, a
throwback to the age of pipe organs, when a pipe’s physical length determined its pitch. The Sub
Phatty’s
OCTAVE
knobs cover four pitch ranges corresponding to four octaves. The lowest setting is
16’, and the highest setting is 2’.
WAVE:
Use this knob to vary either oscillator’s waveform from triangle to sawtooth to square to narrow
pulse wave. Turning the knob clockwise from the triangle to sawtooth position increases the oscillator’s
harmonic content. Continuing to turn it to the square-wave position weakens and then eliminates even-
numbered harmonics while strengthening odd-numbered harmonics. Turning it from the square to
narrow-pulse position changes its harmonic content further by weakening the overtones relative to the
fundamental frequency.
