A phaser is a modulation effect that includes phasers, flangers, and chorus. Phasing is a popular effect in electric guitars. These effects give the impression of movement and constant change. In this sense, modulation refers to as a moment in which a modulator alters a carrier. This carrier is always an audible signal. These three modulation effects use equalization, time delay, or both at the same time to manipulate the signal phase.

The Phaser and the LFO

Engineers often use an LFO to control the speed and depth of the sweeping. For this reason, the LFO operates as the modulator, while the audible signal functions as the carrier. Flanger and chorus effects always use the time delay to create a phaser effect. Notwithstanding, the phaser is quite peculiar since it involves a chain of all-pass filters to create frequency notches and peaks. The movement of notches and peaks produce its unique sound.

The Most Common Electronic Phasers

The most common electronic phasers use a set of variable all-pass past-shift networks that alter the phases of different frequency components of a specific signal. These networks set several frequencies to an equal volume. However, the human ears can’t really react to phase differences. These networks can create a certain interference when they fuse an unprocessed signal. As a result, notches emerge.

All-Pass Filters

All-pass filters, also known as stages, are different within the various models of phasers. Analog ones provide from four to twelve stages, whereas digitals offer over 32. The number of stages has a direct impact over notches in a specific sound.

Phaser Today

Around the 1960s this effect was widely common when referring to the original flanging effect heard on many psychedelic records. The phasing effect became quite popular for guitarists such as Robin Trower and Jimi Hendrix. Afterwards, in the 1970s, it became available as a portable guitar effect.

Nowadays, musicians employ phasers in motion pictures, as well as in television production. Phaser turn human voices into robotic expressions. The frequency filtering creates sounds that mimic mechanical sources, so this technique works quite well.