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. While most frequently used with electric or electronic instruments, effects can also be used with acoustic instruments, drums and vocals. Examples of common effects units include wah-wah pedals, fuzzboxes and reverb units.
Effects are housed in amplifiers, table top units, "stompboxes" and "rackmounts", or they are built into the instruments themselves. A stompbox (or "pedal") is a small metal or plastic box placed on the floor in front of the musician and connected to his or her instrument. The box is typically controlled by one or more foot-pedal on-off switches and contains only one or two effects. A rackmount is mounted on a standard 19-inch equipment rack and usually contains several different types of effects.
While there is currently no firm consensus on how to categorize effects, the following are seven common classifications: distortion, dynamics, filter, modulation, pitch/frequency, time-based and feedback/sustain. Guitarists derive their signature sound or "tone" from their choice of instrument, pickups, effects units, and guitar amp.
- 1 Formats (form factor)
- 2 History
- 3 Types
- 4 Boutique pedals
- 5 Other pedals and rackmount units
- 6 See also
- 7 References
Formats (form factor)
Effects units are available in a variety of formats or "form factors". Stompbox pedals are usually the smallest, least expensive and most rugged format. Rackmount devices are generally more expensive and offer a wider range of functions. An effects unit can consist of analog or digital circuitry or a combination of the two. During a live performance, the effect is plugged into the electrical "signal" path of the instrument. In the studio, the instrument or other sound-source's auxiliary output is patched into the effect. Form factors are part of a studio or musician's outboard gear.
Stompboxes, or effects pedals, are designed to be positioned on the floor or within a pedalboard and operated with the user's feet. The simplest stompbox pedals have a single footswitch; one to three potentiometers for controlling the effect, gain or tone; and a single LED to indicate if the effect is on. Complex stompbox pedals may have multiple footswitches, large numbers of knobs, additional switches, and an alphanumeric display screen that indicates the status of the effect with short acronyms (e.g. DIST for "distortion").
An "effects chain" or "signal chain" may be formed by connecting two or more stompboxes. Effect chains are typically created between the guitar and the amp or between the preamplifier ("preamp") and the power amp. When a pedal is off or inactive, the electric audio signal coming into the pedal is diverted onto a "bypass", resulting in a "dry" signal which continues on to other effects down the chain. In this way, the effects within a chain can be combined in a variety of ways without having to reconnect boxes during a performance. A "controller" or "effects management system" allows for multiple effect chains to be created, so that one or several chains can be engaged or disengaged by tapping a single switch. The switches are usually organized in a row or a simple grid.
To preserve the clarity of the tone, it is most common to put compression, wah and overdrive pedals at the start of the chain; modulation (chorus, flanger, phase shifter) in the middle; and time-based units (delay/echo, reverb) at the end. When using many effects, unwanted noise and hum can be introduced into the sound. Some performers use a noise gate pedal at the end of a chain to reduce unwanted noise and hum introduced by overdrive units or vintage gear.
Rackmounted effects are built into a case designed to integrate into a 19-inch rack standard to the telecommunication and computing industries. A rackmount unit may contain electronic circuitry identical to a stompbox's, although its circuits are typically more complex. Unlike stompboxes, rackmounts usually have several different types of effects.
Rackmounts are most commonly used in recording studios and "front of house" live sound mixing situations, though many musicians use them in place of stompboxes. Rackmounts are controlled by knobs or switches on their front panel, and often by a MIDI digital control interface. During live performances, a musician can operate rackmounted effects using a "foot controller".
"Shock mount" racks are designed for musicians who are shipping gear on major tours. Devices that are less than 19 inches wide may use special "ear" adapters that allow them to be mounted on a rack.
Effects are often incorporated into amplifiers and even some types of instruments. Electric guitar amplifiers typically have built-in reverb and distortion, while acoustic guitar and keyboard amplifiers tend to only have built-in reverb. The Fender Bandmaster Reverb, for example, had built-in reverb and vibrato.
Since the 2000s, guitar amplifiers began having built-in multi-effects units or digital modeling effects. Bass amplifiers are less likely to have built-in effects, although some may have a compressor/limiter or distortion. Instruments with built-in effects include Hammond organs, electronic organs, electronic pianos and digital synthesizers. Occasionally, acoustic-electric and electric guitars will have built-in effects, such as a preamp or equalizer.
Multi-effects and tabletop units
A multi-effects device (also called a "multi-FX" device) is a single electronics effects pedal or rackmount device that contains many different electronic effects. Multi-FX devices allow users to "preset" combinations of different effects, allowing musicians quick on-stage access to different effects combinations.
A tabletop unit is a type of multi-effects device that sits on a desk and is controlled manually. One such example is the Pod guitar amplifier modeler. Digital effects designed for DJs are often sold in tabletop models, so that the units can be placed alongside a mixer, turntables and CD scratching gear.
Studio effects and early stand alone units
The earliest sound effects were strictly studio productions. In the mid to late 1940s, recording engineers and experimental musicians such as Les Paul began manipulating reel-to-reel recording tape to create echo effects and unusual, futuristic sounds. Microphone placement ("miking") techniques were used in spaces with specially designed acoustic properties to simulate echo chambers.
In 1948 DeArmond released the Trem-Trol, the first commercially available stand-alone effects unit. This device produced a tremolo by passing an instrument's electrical signal through a water-based electrolytic fluid. Most stand-alone effects of the 1950s and early 60s such as the Gibson GA-VI vibrato unit and the Fender reverb box, were expensive and impractical, requiring bulky transformers and high voltages. The original stand-alone units were not especially in-demand as many effects came built into amplifiers. The first popular stand-alone was the 1958 Watkins Copicat, a relatively portable tape echo effect made famous by the British band, The Shadows.
Amplifier built-ins were the first effects to be used regularly outside the studio by guitar players. From the late 1940s onward, the Gibson Guitar Corp. began including vibrato circuits in combo amplifiers. The 1950 Ray Butts EchoSonic amp was the first to feature the "slapback" echo sound, which quickly became popular with guitarists such as Chet Atkins, Carl Perkins, Scotty Moore, Luther Perkins, and Roy Orbison. By the 1950s, tremolo, vibrato and reverb were available as built-in effects on many guitar amplifiers. Both Premier and Gibson built tube-powered amps with spring reverb. Fender began manufacturing the tremolo amps Tremolux in 1955 and Vibrolux in 1956.
Distortion was not an effect originally intended by amplifier manufacturers, but could often easily be achieved by "overdriving" the power supply in early tube amplifiers. In the 1950s, guitarists began deliberately increasing gain beyond its intended levels to achieve "warm" distorted sounds. Among the first musicians to experiment with distortion were Willie Johnson of Howlin' Wolf, Goree Carter, Joe Hill Louis, Ike Turner, Guitar Slim, and Chuck Berry.
In 1954 Pat Hare produced heavily distorted power chords for several recordings (including James Cotton's Cotton Crop Blues"), creating "a grittier, nastier, more ferocious electric guitar sound," accomplished by turning the volume knob on his amplifier "all the way to the right until the speaker was screaming." Link Wray's 1958 recording "Rumble" inspired young musicians such as Pete Townshend of The Who, Jimmy Page of Led Zeppelin, Jeff Beck, Dave Davies of The Kinks, and Neil Young to explore distortion. Davies would famously doctor the speakers of his amp by slitting them with a razor blade to achieve a grittier guitar sound on the 1964 song "You Really Got Me". In 1966, the British company Marshall Amplification began producing the Marshall 1963, a guitar amplifier capable of producing the distorted "crunch" that rock musicians were starting to seek.
The electronic transistor finally made it possible to cram the aural creativity of the recording studio into small, highly portable stompbox units. Transistors replaced vacuum tubes, allowing for much more compact formats and greater stability. The first transistorized guitar effect was the 1962 Maestro Fuzz Tone pedal, which became a sensation after its use in the 1965 Rolling Stones hit "(I Can't Get No) Satisfaction".
Warwick Electronics manufactured the first wah-wah pedal, The Clyde McCoy, in 1967 and that same year Jim Morris of Kelsey-Morris Sound developed the first octave effect, which Jimi Hendrix named "Octavio." In 1968, Univox began marketing its Uni-Vibe pedal, an effect designed by noted audio engineer Fumio Mieda that mimicked the odd phase shift and chorus effects of the Leslie rotating speakers used in Hammond organs. The pedals soon became favorite effects of guitarists Jimi Hendrix and Robin Trower. Upon first hearing the Octavia, Hendrix allegedly rushed back to the studio and immediately used it to record the guitar solos on "Purple Haze" and "Fire" By the mid-1970s a variety of solid-state effects pedals including flangers, chorus pedals, ring modulators and phase shifters were available.
In the 1980s, digitized rackmount units began replacing stompboxes as the effects format of choice. Often musicians would record "dry", unaltered tracks in the studio and effects would be added in post-production. The success of Nirvana's 1991 album Nevermind helped to re-ignite interest in stompboxes. Throughout the 1990s, musicians committed to a "lo-fi" aesthic such as J Mascis of Dinosaur Jr., Stephen Malkmus of Pavement and Robert Pollard of Guided by Voices continued to use analog effects pedals.
Effects and effects units—stompboxes in particular—have been celebrated by pop and rock musicians in album titles, songs and band names. The Big Muff, a classic fuzzbox manufactured by Electro-Harmonix, is commemorated by the Depeche Mode song "Big Muff" and the Mudhoney EP Superfuzz Bigmuff. Nine Inch Nails, Pink Floyd, George Harrison, They Might Be Giants and Joy Division are among the many musicians who have referenced effects units in their music.
Temporal vs Dynamic Effects
Audio effects can generally separated into two categories, dynamic effects that affect the volume of a sound signal, such as distortion, compression and equalization, and temporal effects which affect the time, phase and frequency of the signal, such as reverb, delay, phazer, and pitch shifting/auto-harmony. It is normal (but not required) for dynamic effects to be used as an *Insert* on a channel or group, and temporal effects to be used on an *aux send*.
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Distortion effects create "warm", "gritty" and "fuzzy" sounds by "clipping" an instrument's audio signal, which distorts the shape of its wave form and adds overtones. Distortion effects are sometimes called "gain" effects, as distorted guitar sounds were first achieved by increasing the electric power supply, e.g. gain, to tube amplifiers.
Distortion and overdrive: Distortion and overdrive units re-shape or "clip" an audio signal's wave form so that it has flattened peaks, creating "warm" sounds by adding harmonics or "gritty" sounds by adding inharmonic overtones. In tube amplifiers, distortion is created by compressing the instrument's out-going electrical signal in vacuum tubes or "valves". Distortion pedals produce perfectly flattened peaks or "hard" clipping. Overdrive pedals produce "soft” tube-like distortion by compressing the sine wave without completely flattening it. Much like tube amps, overdrive units produce "clean" sounds at quieter volumes and distorted "warm" sounds at louder volumes. Distortion and overdrive pedals may either be transistor-based or digital.
Distortion and overdrive effects: Boss DS-1 Distortion, Ibanez Tube Screamer, Marshall ShredMaster, MXR Distortion +, Pro Co RAT.
Fuzz: A fuzz pedal or "fuzzbox" is a type of overdrive pedal that clips a sound-wave until it is nearly a squarewave, resulting in a heavily distorted or "fuzzy" sound. Fuzzboxes may contain frequency multiplier circuitry to achieve a harsh timbre by adding complex harmonics. The Rolling Stones' "(I Can't Get No) Satisfaction" greatly popularized the use of fuzz effects. Fuzz bass (also called "bass overdrive") is a style of playing the electric bass that produces a buzzy, overdriven sound via a tube or transistor amp or by using a fuzz or overdrive pedal.
Fuzz effects: Arbiter Fuzz Face, Electro-Harmonix Big Muff, Shin-ei Companion FY-2, Univox Super-Fuzz, Vox Tone Bender, Z.Vex Fuzz Factory.
Boost/volume pedal: A boost or "clean boost" amplifies the volume of an instrument by increasing the amplitude of its audio signal. These units are generally used for "boosting" volume during solos and preventing signal loss in long "effects chains". A guitarist switching from rhythm guitar to lead guitar may use a boost to increase the volume of his or her solo.
Treadle based volume pedals are often also used to create swelling effects by removing the attack of a note or chord, as popularised by pedal steel guitar players. Volume effects: Electro-Harmonix LPB-1, Fender Volume Pedal, MXR Micro Amp.
Compressor: Compressors make loud sounds quieter and quiet sounds louder by decreasing or "compressing" the dynamic range of an audio signal. A compressor is often used to stabilize volume and smooth a note's "attack" by dampening its onset and amplifying its sustain. A compressor can also function as a limiter with extreme settings of its controls.
Compressor effects: Keeley Compressor, MXR Dyna Comp.
Noise gate: Noise gates eliminate "hum", "hiss" and "static" by greatly diminishing the volume of sounds that fall below a set threshold. Noise gates are expanders, meaning unlike compressors they increase the dynamic range of an audio signal in order to make quiet sounds even quieter. If used with extreme settings along with reverb, they can create unusual sounds, such as the gated drum effect used in 1980s pop songs, a style popularized by the Phil Collins song "In the Air Tonight".
Noise gate effects: Boss NS-2 Noise Suppressor.
Equalizer: An equalizer is a set of linear filters that strengthen ("boost") or weaken ("cut") specific frequency regions. While home stereos often have equalizers for two bands, to adjust bass and treble, professional graphic equalizers offer much more targeted control over the audio frequency spectrum. Audio engineers use highly sophisticated equalizers to eliminate unwanted sounds, make an instrument or voice more prominent, and enhance particular aspects of an instrument's tone.
Equalizer effects: Boss GE-7 Equalizer, MXR 10-band EQ Pedal.
Talk box: A talk box directs the sound from a guitar or synthesizer into the mouth of a performer, allowing him or her to shape the sound into vowels and consonants. The modified sound is then picked up by a microphone. In this way the guitar is able to "talk". Some famous uses of the talkbox include Bon Jovi's "Livin' on a Prayer", Stevie Wonder's "Black Man", Mötley Crüe's "Kickstart My Heart", Joe Walsh's "Rocky Mountain Way", Alice in Chains's "Man in the box" and Peter Frampton's "Show Me the Way".
Talk boxes: Dunlop HT1 Heil Talk Box, Rocktron Banshee.
Wah-wah: A wah-wah pedal creates vowel-like sounds by altering the frequency spectrum produced by an instrument—i.e., how loud it is at each separate frequency—in what is known as a spectral glide or "sweep". The device is operated by a foot treadle that opens and closes a potentiometer. Wah-wah pedals are often used by funk and rock guitarists.
Wah effects: Dunlop Cry Baby, Morley Power Wah, Musitronics Mu-Tron III.
The chorus effect comes from an Electro-Harmonix Small Clone
A short sample followed by two flanging versions
Unprocessed organ followed by different phasing effects
Notice the bell-like sound
A low-frequency oscillator modulating a tremolo
A low-frequency oscillator modulating a vibrato
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Modulation is a control feature rather than a specific architecture wherein one(or more) processing parameters effecting an audio signal is varied over time in order to create sounds with unusual tonal properties. Some modulation effects mix ("modulate") an instrument's audio signal with a signal generated by the effect called a carrier wave. Other modulation effects split an instrument's audio signal in two, altering one portion of the signal and mixing it with the unaltered portion.
Chorus: Chorus pedals mimic the effect choirs and string orchestras produce naturally, by having slight variations in timbre and pitch, by mixing sounds with slight differences in timbre and pitch. A chorus effect splits the instrument-to-amplifier audio signal, and adds a slight delay and frequency variations or "vibrato" to part of the signal while leaving the rest unaltered. A well-known usage of chorus is the lead guitar in "Come As You Are" by Nirvana.
Chorus effects: Boss CE-1 Chorus Ensemble, Electro-Harmonix Small Clone, TC Electronic Stereo Chorus.
Flanger: A flanger creates a "jet plane" or "spaceship" sound, simulating a studio effect produced by recording a track on two synchronized tapes and periodically slowing one tape by pressing the edge of its reel (the "flange"). When the two tapes' audio signals are later mixed, a comb filter effect can be heard. Flanger units add a variably delayed version of the audio signal to the original or signal, creating a comb filter or Doppler effect. Some famous uses of flanger effects include "Walking on the Moon" by The Police, the intro to "Ain't Talkin' 'Bout Love" by Van Halen, and "Barracuda" by Heart.
Flanger effects: Electro-Harmonix Electric Mistress, MXR Flanger.
Phaser: A phaser or "phase shifter" creates a slight rippling effect—amplifying some aspects of the tone while diminishing others—by splitting an audio signal in two and altering the phase of one portion. Three well-known examples of phaser are the two handed tapping part on the Van Halen instrumental Eruption and the keyboard parts on Billy Joel's "Just the Way You Are" and Paul Simon's "Slip Slidin' Away".
Phase shift effects: Electro-Harmonix Small Stone, MXR Phase 90, Univox Uni-Vibe.
Ring modulator: A ring modulator produces a resonant, metallic sound by mixing an instrument's audio signal with a carrier wave generated by the device's internal oscillator. The original sound wave is suppressed and replaced by a "ring" of inharmonic higher and lower pitches or "sidebands". A notable use of ring modulation is the guitar in the Black Sabbath song "Paranoid".
Ring modulator effects: moogerfooger MF-102 Ring Modulator.
Tremolo: A tremolo effect produces a slight, rapid variation in the volume of a note or chord. The "tremolo effect" should not be confused with the misleadingly-named "tremolo bar", a device on a guitar bridge that creates a vibrato or "pitch-bending" effect. In transistorized effects, a tremolo is produced by mixing an instrument's audio signal with a sub-audible carrier wave in such a way that generates amplitude variations in the sound wave. The guitar intro in the Rolling Stones' "Gimme Shelter" features a tremolo effect.
Tremolo effects: Demeter TRM-1 Tremulator, Fender Tremolux.
Vibrato: Vibrato effects produce slight, rapid variations in pitch, mimicking the fractional semitone variations produced naturally by opera singers and violinists when prolonging a single note. Vibrato effects often allow the performer to control the rate of the variation as well as the difference in pitch (e.g. "depth"). A vibrato with an extreme "depth" setting (e.g., half a semitone or more) will produce a dramatic, ululating sound. In transistorized effects, vibrato is produced by mixing an instrument's audio signal with a carrier wave in such a way that generates frequency variations in the sound wave. Guitarists often use the terms "vibrato" and "tremolo" misleadingly. A so-called "vibrato unit" in a guitar amplifier actually produces tremolo, while a "tremolo arm" or "whammy bar" on a guitar produces vibrato. Vibrato effects: Boss VB-2 Vibrato.
Pitch shifter and harmonizer: A pitch shifter raises or lowers (e.g. "transposes") each note a performer plays by a pre-set interval. For example, a pitch shifter set to increase the pitch by a fourth will raise each note four diatonic intervals above the notes actually played. Simple pitch shifters raise or lower the pitch by one or two octaves, while more sophisticated devices offer a range of interval alterations.
A harmonizer is a type of pitch shifter that combines the altered pitch with the original pitch to create a two or more note harmony. Some hamonizers are able to create chorus-like effects by adding very tiny shifts in pitch.
Pitch shift effects: DigiTech Whammy, Electro-Harmonix POG.
Time-based effects delay the sound signal or adds echos.
A flute before and after delay
Reverb with increasingly longer decay times
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Delay/echo: Delay/echo units produce an echo effect by adding a duplicate instrument-to-amplifier electrical signal to the original signal at a slight time-delay. The effect can either be a single echo called a "slap" or "slapback," or multiple echos. A well-known use of delay is the lead guitar in the U2 song "Where the Streets Have No Name".
Delay effects: Boss DD-3 Digital Delay, Electro-Harmonix Deluxe Memory Man, Line 6 DL4, Roland RE-201.
Looper pedal: A looper pedal or "phrase looper" allows a performer to record and later replay a phrase or passage from a song. Loops can be created on the spot during a performance (live looping) or they can be pre-recorded. Some units allow a performer to layer multiple loops. The first loop effects were created with reel-to-reel tape using a tape loop. High-end boutique tape loop effects are still used by some studios who want a vintage sound. Digital loop effects recreate this effect using an electronic memory.
Looper effects: Boss RC-30 Loop Station.
Reverb: Reverb units simulate sounds produced in a finite acoustic space by creating a large number of echoes that gradually fade or "decay". One early technique for creating a reverb effect was to send an amplified signal of the music to room with reflective surfaces, such as a tile bathroom, and then record the natural reverberations. A plate reverb system uses an electromechanical transducer to create vibrations in a plate of metal. Spring reverb systems, which are often used in guitar amplifiers, use a transducer to create vibrations in a spring. Digital reverb effects use various signal processing algorithms to create the reverb effect, often by using multiple feedback delay circuits. Rockabilly and surf guitar are two genres that make heavy use of reverb.
Reverb effects: Electro-Harmonix Holy Grail, Fender Reverb Unit.
Audio feedback: Audio feedback is an effect produced when amplified sound is picked up by a microphone and played back through an amplifier, initiating a "feedback loop". Feedback as pioneered by guitarists such as Jimi Hendrix is generated by playing an instrument directly in front of an amplifier set to a high volume. This relatively primitive technique tends to create high-pitched overtones and can be difficult to sustain. It can also be hard to determine the sound volume and guitar position relative to a loudspeaker necessary for achieving feedback conditions.
EBow is a brand name of Heet Sound Products, of Los Angeles, California, for the original type of small handheld resonator, invented by Greg Heet. The resonator uses a pickup - inductive string driver - feedback circuit, including a sensor coil, driver coil, and amplifier, to induce forced string resonance. The Ebow brand resonator is monophonic, and drives only one string at a time; Other handheld guitar and bass resonators on the market, manufactured under the tradename SRG, produced by Aescher Europa, in Germany, are available in both monophonic and polyphonic models, which include multiple onboard trigger switch effects, such as HPF (high pass filter) for enhancing harmonics and producing feedback effects, and LPF (low pass filter), producing a bass boost with a cello sound on heavy gauge strings. Later EBow models, such as the plus Ebow, contain a mode slide switch on the back, which allows the player to either produce just sustain or overtone feedback in addition to sustain.
Many compressor pedals are often also marketed as "sustainer pedals". As a note is sustained, it loses energy and volume due to diminishing vibration in the string. The compressor pedal boosts its electrical signal to the specified dynamic range, slightly prolonging the duration of the note. This, combined with heavy distortion and the close proximity of the guitar and the speaker cabinet, can lead to infinite sustain at higher volumes.
Envelope follower: An envelope follower activates an effect once a designated volume is reached. One effect that uses an envelope follower is the "auto-wah", which produces a "wah" effect depending on how loud or soft the notes are being played.
Guitar amplifier modeling: Amplifier modeling is a digital effect that replicates the sound of various amplifiers, most often analog "tube" amps. Sophisticated modeling effects can simulate speaker cabinets and miking techniques. A rotary speaker simulator mimics the doppler sound of a vintage Leslie speaker system by replicating its volume and pitch modulations, overdrive capacity and phase shifts.
Simulators: Simulators enable electric guitars to mimic the sound of other instruments such as acoustic guitar, electric bass and sitar. Pick up simulators used on guitars with single-coil pick ups replicate the sound of guitars with humbucker pick ups, or vice versa. A de-fretter is a bass guitar effect that simulates the sound of a fretless bass. The effect uses an envelope-controlled filter and voltage-controlled amplifier to "soften" a note's attack both in volume and timbre.
Rotating speakers are specially constructed amplifier/loudspeakers used to create special audio effects using the Doppler effect by rotating the speakers or a sound-directing duct. The rotating speaker creates a chorus-type effect. Named after its inventor, Donald Leslie, it is particularly associated with the Hammond organ but is used with a variety of instruments as well as vocals. The Hammond/Leslie combination has become an element in many genres of music. The Leslie Speaker and the Hammond Organ brands are currently owned by Suzuki Musical Instrument Corporation. The stompbox that simulates this effect is the Uni-Vibe pedal.
Some electronic effects are designed specifically for the electric bass, including fuzz bass, an overdrive or distortion pedal designed for bass, and bass chorus, a chorus effect designed for the electric bass. In both cases, the effects are optimized to work with the low pitch range of the bass.
Boutique pedals are designed by smaller, independent companies and are typically produced in limited quantities. Some may even be hand-made, with hand-soldered connections. These pedals are mainly distributed online or through mail-order, or sold in a few music stores. They are often more expensive than mass-produced pedals and offer non-standard features such as true-bypass switching, higher-quality components, innovative designs, in-house-made knobs and hand-painted artwork or etching. Some boutique companies focus on re-creating classic or vintage effects.
Some boutique pedal manufacturers include: Analog Man, BJFE, Pete Cornish, Emlyn Crowther, Death By Audio, Devi Ever, Robert Keeley, Roger Linn, Roger Mayer, Strymon, T-Rex Engineering, ToadWorks and Z.Vex Effects.
Effects unit modification
There is also a niche market for modifying or "modding" effects. Typically, vendors provide either custom modification services or sell new effects pedals which have been modified. The Ibanez Tube Screamer, Boss DS-1, Pro Co RAT and DigiTech Whammy are some of the most often-modified effects. Common modifications include value changes in capacitors or resistors, adding true-bypass so that the effect's circuitry is no longer in the signal path, substituting higher-quality components, replacing the unit's original operational amplifiers (op-amps), or adding functions to the device, such as allowing additional control of some factor or adding another output jack.
Other pedals and rackmount units
Not all stompboxes and rackmounted electronic devices designed for musicians are effects. Strobe tuner and regular electronic tuner pedals indicate whether a guitar string is too sharp or flat. A footswitch pedal such as the "A/B" pedal routes a guitar signal to an amplifier or enables a performer to switch between two guitars, or between two amplifiers.
Guitar amplifiers and electronic keyboards may have switch pedals for turning built-in reverb and distortion effects on and off; the pedals contain only a switch, with the circuitry for the effect being housed in the amplifier chassis. Some musicians who use rackmounted effects or laptops employ a MIDI controller pedalboard or armband remote controls to trigger sound samples, switch between different effects or control effect settings.
- Audio effects
- Outboard gear — for more generic article
- Sound effect
- Audio signal processing
- Acoustic wave — for natural audio effects
- Vintage musical equipment
- Digital signal processor
- Linear filter
- Non-linear filter
- Frequency divider
- Frequency mixer
- Frequency multiplier
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