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Phaser (effect)
Encyclopedia
A phaser is an audio signal processing
technique used to filter
a signal by creating a series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs is typically modulated
so that they vary over time, creating a sweeping effect. For this purpose, phasers usually include a low-frequency oscillator.
The electronic phasing effect is created by splitting an audio signal into two paths. One path treats the signal with an all-pass filter
, which preserves the amplitude of the original signal and alters the phase. The amount of change in phase depends on the frequency. When signals from the two paths are mixed, the frequencies that are out of phase will cancel each other out, creating the phaser's characteristic notches. Changing the mix ratio changes the depth of the notches; the deepest notches occur when the mix ratio is 50%.
The definition of phaser typically excludes such devices where the all-pass section is a delay line
; such a device is called a flanger. Using a delay line
creates an unlimited series of equally spaced notches and peaks. It is possible to cascade a delay line with another type of all-pass filter as in, this combines the unlimited number of notches from the flanger with the uneven spacing of the phaser.
phase-shift networks which alter the phases of the different frequency components in the signal. These networks pass all frequencies at equal volume, introducing only phase change to the signal. Human ears are not very responsive to phase differences, but this creates audible interferences when mixed back with the dry (unprocessed) signal, creating notches. The simplified structure of a mono phaser is shown below:
The number of all-pass filter
s (usually called stages) varies with different models, some analog phasers offer 4, 6, 8 or 12 stages. Digital phasers may offer up to 32 or even more. This determines the number of notches/peaks in the sound, affecting the general sound character. A phaser with n stages generally has n/2 notches in the spectrum, so a 4-stage phaser will have two notches.
Additionally, the output can be fed back to the input for a more intense effect, creating a resonant effect by emphasizing frequencies between notches. This involves feeding the output of the all-pass filter chain back to the input, as shown here:
The frequency response of an 8-stage phaser with or without feedback is shown. Note that the peaks between the notches are sharper when there's feedback, giving a distinct sound.
A stereo
phaser is usually two identical phasers modulated by a quadrature
signal; the output of the oscillators for the left and right channels are a quarter-wave out of phase.
Most modern phasers are a part of a digital signal processor
, often trying to emulate analog phasers. Phasers are mostly found as plugins for sound editing software, as a part of a monolithic rackmount sound effect unit, or as "stompbox" guitar effects.
. The term was often used to refer the original tape flanging
effect heard on many psychedelic records of the late 1960s, notably "Itchycoo Park
" by the Small Faces and "Life in the Fast Lane
" by The Eagles. By the early 1970s, phasing was available as a portable guitar effect
, one of the most notable early examples being the MXR Phase 90
. From 1974, Steve Hackett
in Selling England by the Pound
studio album and tour used this one for his Les Pauls, and from The Lamb Lies Down On Broadway
album and tour used the "phase filter" section in his EMS Synthi Hi-Fli. In the late 1970s, Brian May
used large amounts of phasing, in such songs as "Sheer Heart Attack." In the 1980s, Eddie Van Halen
, for instance, often used the MXR Phase 90 as part of his signal chain.
Keyboard players also used phasing: in the 1970s, keyboard instrument
s like the Rhodes
, the Eminent 310, and the Clavinet
were commonly treated with a phaser, especially in avant-garde jazz
. Bill Evans
, for instance, used a Maestro phaser on Intuition
. The phaser is also used to "sweeten" their sounds. Examples can be heard in Billy Joel
's "Just The Way You Are", Styx
's "Babe", and Jean Michel Jarre
's Oxygène
. Tony Banks
(Genesis
) used an MXR
Phase 100 on his RMI 368x Electra piano from 1974 (later he will insert this effect, as well as the fuzzbox, into the Electra's panel); from late 1977 he will also use the phaser (with a Boss
CE-1 too) on his Hammond organ, for replacing the Leslie's rotating effect.
In motion picture
or television
production, the effect created by a phaser is often used to imply that the sound is synthetically generated, like turning a natural human voice into a computer or robot voice. The technique works because the frequency filtering produces sound commonly associated with mechanical sources, which only generate specific frequencies, rather than natural sources, which produce a range of frequencies. A vocoder
is a different effect used for similar purposes.
is a similar effect, in which the notches are linearly spaced. In a flanger effect, the notches are created by mixing the signal with a delay
ed version of itself. Flangers tend to sound more pronounced and natural, like the "jet plane whoosh" effect, whereas phasers tend to sound more subtle and otherworldy. For comparison of the two effects, check flanging.
Audio signal processing
Audio signal processing, sometimes referred to as audio processing, is the intentional alteration of auditory signals, or sound. As audio signals may be electronically represented in either digital or analog format, signal processing may occur in either domain...
technique used to filter
Audio filter
An audio filter is a frequency dependent amplifier circuit, working in the audio frequency range, 0 Hz to beyond 20 kHz. Many types of filters exist for applications including graphic equalizers, synthesizers, sound effects, CD players and virtual reality systems.Being a frequency dependent...
a signal by creating a series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs is typically modulated
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
so that they vary over time, creating a sweeping effect. For this purpose, phasers usually include a low-frequency oscillator.
Process
All-pass filter
An all-pass filter is a signal processing filter that passes all frequencies equally, but changes the phase relationship between various frequencies. It does this by varying its propagation delay with frequency...
, which preserves the amplitude of the original signal and alters the phase. The amount of change in phase depends on the frequency. When signals from the two paths are mixed, the frequencies that are out of phase will cancel each other out, creating the phaser's characteristic notches. Changing the mix ratio changes the depth of the notches; the deepest notches occur when the mix ratio is 50%.
The definition of phaser typically excludes such devices where the all-pass section is a delay line
Delay line
Delay line may refer to:* Propagation delay, the length of time taken for something to reach its destination* Analog delay line, used to delay a signal...
; such a device is called a flanger. Using a delay line
Delay line
Delay line may refer to:* Propagation delay, the length of time taken for something to reach its destination* Analog delay line, used to delay a signal...
creates an unlimited series of equally spaced notches and peaks. It is possible to cascade a delay line with another type of all-pass filter as in, this combines the unlimited number of notches from the flanger with the uneven spacing of the phaser.
Structure
Traditional electronic phasers use a series of variable all-passAll-pass filter
An all-pass filter is a signal processing filter that passes all frequencies equally, but changes the phase relationship between various frequencies. It does this by varying its propagation delay with frequency...
phase-shift networks which alter the phases of the different frequency components in the signal. These networks pass all frequencies at equal volume, introducing only phase change to the signal. Human ears are not very responsive to phase differences, but this creates audible interferences when mixed back with the dry (unprocessed) signal, creating notches. The simplified structure of a mono phaser is shown below:
All-pass filter
An all-pass filter is a signal processing filter that passes all frequencies equally, but changes the phase relationship between various frequencies. It does this by varying its propagation delay with frequency...
s (usually called stages) varies with different models, some analog phasers offer 4, 6, 8 or 12 stages. Digital phasers may offer up to 32 or even more. This determines the number of notches/peaks in the sound, affecting the general sound character. A phaser with n stages generally has n/2 notches in the spectrum, so a 4-stage phaser will have two notches.
Additionally, the output can be fed back to the input for a more intense effect, creating a resonant effect by emphasizing frequencies between notches. This involves feeding the output of the all-pass filter chain back to the input, as shown here:
A stereo
STEREO
STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...
phaser is usually two identical phasers modulated by a quadrature
Quadrature
Quadrature may refer to:In signal processing:*Quadrature amplitude modulation , a modulation method of using both an carrier wave and a 'quadrature' carrier wave that is 90° out of phase with the main, or in-phase, carrier...
signal; the output of the oscillators for the left and right channels are a quarter-wave out of phase.
Most modern phasers are a part of a digital signal processor
Digital signal processor
A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...
, often trying to emulate analog phasers. Phasers are mostly found as plugins for sound editing software, as a part of a monolithic rackmount sound effect unit, or as "stompbox" guitar effects.
Usage
Phasing is a popular effect for electric guitarElectric guitar
An electric guitar is a guitar that uses the principle of direct electromagnetic induction to convert vibrations of its metal strings into electric audio signals. The signal generated by an electric guitar is too weak to drive a loudspeaker, so it is amplified before sending it to a loudspeaker...
. The term was often used to refer the original tape flanging
Flanging
Flanging is an audio effect produced by mixing two identical signals together, with one signal delayed by a small and gradually changing period, usually smaller than 20 milliseconds. This produces a swept comb filter effect: peaks and notches are produced in the resultant frequency spectrum,...
effect heard on many psychedelic records of the late 1960s, notably "Itchycoo Park
Itchycoo Park
"Itchycoo Park" is a psychedelic pop song written by Steve Marriott and Ronnie Lane, first recorded by their group, the Small Faces. The song reached number three in the UK Singles Chart, 1967.-Song profile:...
" by the Small Faces and "Life in the Fast Lane
Life in the Fast Lane
"Life in the Fast Lane" is a song written by Joe Walsh, Glenn Frey and Don Henley and recorded by the American rock band Eagles on their 1976 studio album Hotel California...
" by The Eagles. By the early 1970s, phasing was available as a portable guitar effect
Effects unit
Effects units are electronic devices that alter how a musical instrument or other audio source sounds. Some effects subtly "color" a sound, while others transform it dramatically. Effects are used during live performances or in the studio, typically with electric guitar, keyboard and bass...
, one of the most notable early examples being the MXR Phase 90
MXR Phase 90
The MXR Phase 90 is a phaser effects pedal originally designed in the 1970s by MXR.-History:The Phase 90 was released in 1972. It was the first pedal sold by MXR and helped launch the company. The original came in a simple orange enclosure with MXR's "script" logo. In 1977 MXR changed its logo to...
. From 1974, Steve Hackett
Steve Hackett
Stephen Richard Hackett is a British singer-songwriter and guitarist. He gained prominence as a member of the British progressive rock group Genesis, which he joined in 1970 and left in 1977 to pursue a solo career...
in Selling England by the Pound
Selling England by the Pound
- Sound and live performance :The piano introduction to "Firth of Fifth" has not been included in a performance since 1974, in a Drury Lane Theatre concert, when Banks misplayed and Collins covered by starting the song from after the intro...
studio album and tour used this one for his Les Pauls, and from The Lamb Lies Down On Broadway
The Lamb Lies down on Broadway
The Lamb Lies Down on Broadway is a double concept album recorded and released in 1974 by the British rock band Genesis. It was their sixth studio album and the last album by the group to feature the involvement of lead singer Peter Gabriel.-Premise:...
album and tour used the "phase filter" section in his EMS Synthi Hi-Fli. In the late 1970s, Brian May
Brian May
Brian Harold May, CBE is an English musician and astrophysicist most widely known as the guitarist and a songwriter of the rock band Queen...
used large amounts of phasing, in such songs as "Sheer Heart Attack." In the 1980s, Eddie Van Halen
Eddie Van Halen
Edward Lodewijk "Eddie" Van Halen is a Dutch-American guitarist, keyboardist, songwriter and producer, best known as the lead guitarist and co-founder of the hard rock band Van Halen, inducted into the Rock and Roll Hall of Fame...
, for instance, often used the MXR Phase 90 as part of his signal chain.
Keyboard players also used phasing: in the 1970s, keyboard instrument
Keyboard instrument
A keyboard instrument is a musical instrument which is played using a musical keyboard. The most common of these is the piano. Other widely used keyboard instruments include organs of various types as well as other mechanical, electromechanical and electronic instruments...
s like the Rhodes
Rhodes piano
The Rhodes piano is an electro-mechanical piano, invented by Harold Rhodes during the fifties and later manufactured in a number of models, first in collaboration with Fender and after 1965 by CBS....
, the Eminent 310, and the Clavinet
Clavinet
A Clavinet is an electrically amplified keyboard instrument manufactured by the Hohner company. It is essentially an electronically amplified clavichord, analogous to an electric guitar. Its distinctive bright staccato sound has appeared particularly in funk, disco, rock, and reggae songs.Various...
were commonly treated with a phaser, especially in avant-garde jazz
Avant-garde jazz
Avant-garde jazz is a style of music and improvisation that combines avant-garde art music and composition with jazz. Avant-jazz often sounds very similar to free jazz, but differs in that, despite its distinct departure from traditional harmony, it has a predetermined structure over which ...
. Bill Evans
Bill Evans
William John Evans, known as Bill Evans was an American jazz pianist. His use of impressionist harmony, inventive interpretation of traditional jazz repertoire, and trademark rhythmically independent, "singing" melodic lines influenced a generation of pianists including: Chick Corea, Herbie...
, for instance, used a Maestro phaser on Intuition
Intuition (Bill Evans album)
Intuition is an album by jazz pianist Bill Evans, released in 1974 . It was reissued on CD by Original Jazz Classics in 1995.-Reception:The Allmusic review awarded the album 4 stars.-Track listing:...
. The phaser is also used to "sweeten" their sounds. Examples can be heard in Billy Joel
Billy Joel
William Martin "Billy" Joel is an American musician and pianist, singer-songwriter, and classical composer. Since releasing his first hit song, "Piano Man", in 1973, Joel has become the sixth best-selling recording artist and the third best-selling solo artist in the United States, according to...
's "Just The Way You Are", Styx
Styx (band)
Styx is an American rock band that became famous for its albums from the late 1970s and early 1980s. The Chicago band is known for melding the style of prog-rock with the power of hard rock guitar, strong ballads, and elements of American musical theater....
's "Babe", and Jean Michel Jarre
Jean Michel Jarre
Jean Michel André Jarre is a French composer, performer and music producer. He is a pioneer in the electronic, ambient and New Age genres, and known as an organiser of outdoor spectacles of his music featuring lights, laser displays, and fireworks.Jarre was raised in Lyon by his mother and...
's Oxygène
Oxygene
Oxygène is an album of instrumental electronic music composed, produced, and performed by the French composer Jean Michel Jarre. It was first released in France in December 1976, on Disques Dreyfus with license to Polydor. The album's international release was in summer 1977...
. Tony Banks
Tony Banks (musician)
This article is about the musician. For other people named Tony Banks, see Tony BanksAnthony George "Tony" Banks is a British composer, and multi-instrumentalist, who performs as a keyboardist and a guitarist...
(Genesis
Genesis (band)
Genesis are an English rock band that formed in 1967. The band currently comprises the longest-tenured members Tony Banks , Mike Rutherford and Phil Collins . Past members Peter Gabriel , Steve Hackett and Anthony Phillips , also played major roles in the band in its early years...
) used an MXR
MXR
MXR, also known as MXR Innovations, was a manufacturer of guitar effects units, co-founded in 1973 by Keith Barr and Terry Sherwood . MXR was based in the United States in Rochester, New York. MXR Innovations, Inc. was incorporated in 1974...
Phase 100 on his RMI 368x Electra piano from 1974 (later he will insert this effect, as well as the fuzzbox, into the Electra's panel); from late 1977 he will also use the phaser (with a Boss
Boss Corporation
Boss is a manufacturer of effects pedals for electric guitar and bass guitar. It is a division of the Roland Corporation, a Japanese manufacturer that specializes in musical equipment and accessories...
CE-1 too) on his Hammond organ, for replacing the Leslie's rotating effect.
In motion picture
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
or television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
production, the effect created by a phaser is often used to imply that the sound is synthetically generated, like turning a natural human voice into a computer or robot voice. The technique works because the frequency filtering produces sound commonly associated with mechanical sources, which only generate specific frequencies, rather than natural sources, which produce a range of frequencies. A vocoder
Vocoder
A vocoder is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder...
is a different effect used for similar purposes.
Similar effects
A specific type of phasing, flangingFlanging
Flanging is an audio effect produced by mixing two identical signals together, with one signal delayed by a small and gradually changing period, usually smaller than 20 milliseconds. This produces a swept comb filter effect: peaks and notches are produced in the resultant frequency spectrum,...
is a similar effect, in which the notches are linearly spaced. In a flanger effect, the notches are created by mixing the signal with a delay
Delay (audio effect)
Delay is an audio effect which records an input signal to an audio storage medium, and then plays it back after a period of time. The delayed signal may either be played back multiple times, or played back into the recording again, to create the sound of a repeating, decaying echo.-Early delay...
ed version of itself. Flangers tend to sound more pronounced and natural, like the "jet plane whoosh" effect, whereas phasers tend to sound more subtle and otherworldy. For comparison of the two effects, check flanging.
External links
- Photos of New & Vintage Phaser-Pedals
- The technology of phase shifters and flangers
- How does a phaser work?, video by Empress Effects