PWM Strings

The Evolver, like many classic analog synths, allows you to modulate (i.e. change/control/affect) the width of your pulse waves (also known as “pulse width”) from a variety of sources. Pulse Width Modulation (PWM for short) is a classic analog synthesizer effect.

The most common method of modulation on many synthesizers is via a simple LFO.

The dictionary defines modulation as: “The variation of a property of an electromagnetic wave or signal, such as its amplitude (volume), frequency (pitch), or phase.”

Since manually changing pulse width results in a change in timbre, one would expect an LFO-modulated pulse width to produce a regularly changing/varying timbre, right?

LFO stands for “Low Frequency Oscillator”.

By “low frequency”, we mean oscillation of fewer than 20 cycles per second (or 20 Hertz, abbreviated Hz).

20 Hz, or cycles per second, is the lowest frequency humans can perceive as pitch. If the LFO was faster than 20 Hz, it’d just be a regular oscillator.

20 Hz is still pretty fast, though, and most LFOs can be set to run far below 1 Hz.

In fact, a "classic" analog string sound comes from modulating the pulse width.

Start with our basic patch.

• Set OSC 3 and 4 Level to 0

• OSC 1 Shape to P-52

• OSC 2 Shape to P-48

• LFO 1 Shape to “tri” (triangle wave)

• LFO 1 Frequency = 42

• LFO 1 Amount = 30

• LFO 1 Destination = O1P (OSC 1 Pulse Width)

• LFO 2 Shape = “tri” (triangle wave)

Упражнение 1:

Дата добавления: 2015-08-20