Effects pedals are electronic or digital devices that modify the tone, pitch, or sound of an electric guitar. Effects can be housed in effects pedals, guitar amplifiers, guitar amplifier simulation software, and rackmount preamplifiers or processors. Electronic effects and signal processing form an important part of the electric guitar tone used in many genres, such as rock, pop, blues, and metal. All these are inserted into the signal path between an electric instrument and the amplifier. They modify the signal coming from the instrument, adding "effects" that change the way it sounds in order to add interest, create more impact or create aural soundscapes.
Guitar effects are also used with other instruments in rock, pop, blues, and metal, such as electronic keyboards and synthesizers. Electric bass players use bass effects, which are designed to work with the low-frequency tones of the bass.
Distortion is an important part of an electric guitar's sound in many genres, particularly for rock, hard rock, and metal. A distortion pedal takes a normal electric guitar signal and combine harmonic multiplication and clipping through the use of analog circuitry to create any number of sounds ranging from a mild vintage blues growl to a 1960s psychedelic fuzz sound to the sound of an highly overdriven tube amp in a metal band. Distortion is essential to the powerful sound of heavy metal music.
There are several different types of distortion effects, each with distinct sonic characteristics. These include overdrive/distortion (or vacuum tube-style distortion), overdrive/crunch, fuzz, and hi-gain.
Overdrive distortion is the most well known of all distortions. Although there aren't many electronic differences between a distortion an overdrive, the main audible one is that a distortion does exactly as the name suggests; distorts and clips the signal no matter what volume is going through it, the amount of distortion usually remains relatively the same. This is where an overdrive differs. Most overdrives are built to emulate the sound of a tube amp overdriving and therefore give the player control of the clipping through dynamics. This simply means that the effect gives a clean sound for quieter volumes and a more clipped or distorted sound for louder volumes.
While the general purpose is to emulate classic "warm-tube" sounds, distortion pedals such as the ones in this list can be distinguished from overdrive pedals in that the intent is to provide players with instant access to the sound of a high-gain Marshall amplifier such as the JCM800 pushed past the point of tonal breakup and into the range of tonal distortion known to electric guitarists as "saturated gain." Although most distortion devices use solid-state circuitry, some "tube distortion" pedals are designed with preamplifier vacuum tubes. In some cases, tube distortion pedals use power tubes or a preamp tube used as a power tube driving a built-in "dummy load." Distortion pedals designed specifically for bass guitar are also available. Some distortion pedals include:
- MXR Distortion+: A distortion which is capable of having a very subtle, soft clipping, right through to a heavily overdriven sound favoured by many modern day heavy and death metal guitarists.
- Pro Co Rat
- Boss DS-1 Distortion
- Marshall Guv'nor
- Line 6 Dr. Distorto
- T-Rex Engineering|T-Rex Engineering's Bloody Mary
- Digitech Hot Head
- Danelectro FAB Distortion
Some distortion effects provide an "overdrive" effect. Either by using a vacuum tube, or by using simulated tube modeling techniques, the top of the wave form is compressed, thus giving a smoother distorted signal than regular distortion effects. When an overdrive effect is used at a high setting, the sound's waveform can become clipped, which imparts a gritty or "dirty" tone, which sounds like a tube amplifier "driven" to its limit. Used in conjunction with an amplifier, especially a tube amplifier, driven to the point of mild tonal breakup, short of what would be generally considered distortion or overdrive, these pedals can produce extremely thick distortion sounds much like those used by Carlos Santana or Eddie Van Halen. Today there is a huge variety of overdrive pedals, and some of them are:
- Ibanez Tube Screamer (TS-9 and TS-808): an overdrive which was built to work with the harmonics of a push-pull tube amp. This effect was made famous by blues guitarist Stevie Ray Vaughan but was and is used by hundreds of prominent guitarists since it's invention.
- BOSS SD-1 Super Overdrive
- BOSS BD-2 Blues Driver
- BOSS OD-3 Overdrive
- Line 6 Crunchtone
- DigiTech Bad Monkey
- N-audio Firesound V3
- Danelectro FAB Overdrive
Fuzz was originally intended to recreate the classic 1960's tone of an overdriven tube amp combined with torn speaker cones. Oldschool guitar players (like Link Wray) (citation needed) would use a screwdriver to poke several holes through the paperboard part of the guitar amp speaker to achieve a similar sound. Since the original designs, more extreme fuzz pedals have been designed and produced, incorporating octave-up effects, oscillation, gating, and greater amounts of distortion.
Some fuzzbox pedals include:
- Z.Vex Fuzz Factory
- Dallas Arbiter Fuzz Face: This was a favorite of Psychedelic rocker Jimi Hendrix who shot this pedal to stardom as he did himself.
- Electro Harmonix Big Muff: Probably the most popular fuzz effects ever designed, the Big Muff is also often used as a sustain pedal and sounds excellent in combination with a wah wah.
- BOSS FZ-5 Fuzz
- Danelectro Cool-Cat Fuzz
Hi-Gain (descended from the more generic electric guitar amplification term high-gain) is the sound most used in heavy metal. High gain in normal electric guitar playing simply references a thick sound produced by heavily overdriven amplifier tubes, a distortion pedal, or some combination of both--the essential component is the typically loud, thick, harmonically rich, and sustaining quality of the tone. However, the Hi-Gain sound of modern pedals is somewhat distinct from, although descended from, this sound. The distortion often produces sounds not possible any other way. Many extreme distortions are either hi-gain or the descendents of such. The Mesa Boogie Triple Rectifier Series of amps are an example.
Some Hi-Gain Pedals Include:
- BOSS MT2 Metal Zone
- DigiTech Death Metal
- Danelectro FAB Metal
- Electro Harmonix Metal Muff with Top Boost
- MXR Dime Distortion: Used by Dimebag Darrell.
- Suhr Riot
A Power-Tube pedal contains a power tube and optional dummy load, or a preamp tube used as a power tube. This allows the device to produce power-tube distortion independently of volume; therefore, power-tube distortion can be used as an effects module in an effects chain.
A Power attenuator enables a player to obtain power-tube distortion independently of listening volume. A power attenuator is a dummy load placed between the guitar amplifier's power tubes and the guitar speaker, or a power-supply based circuit to reduce the plate voltage on the power tubes. Examples of power attenuators are the Marshall PowerBrake and THD HotPlate.
An equalizer adjusts the frequency response in a number of different frequency bands. A graphic equalizer (or "graphic EQ") provides slider controls for a number of frequency region. Each of these bands has a fixed width (Q) and a fixed center-frequency, and as such, the slider changes only the level of the frequency band. The tone controls on guitars, guitar amps, and most pedals are similarly fixed-Q and fixed-frequency, but unlike a graphic EQ, rotary controls are used rather than sliders.
Most parametric EQ pedals (such as the  Boss PQ-4) provide semi-parametric EQ. That is, in addition to level control, each band provides either a center frequency or Q width control. Parametric EQs have rotating controls rather than sliders.
Placement of EQ in a distortion signal processing chain affects the basic guitar amp tone. Using a guitar's rotary tone control potentiometer is a form of pre-distortion EQ. Placing an EQ pedal before a distortion pedal or before a guitar amp's built-in preamp distortion provides preliminary control of the preamp distortion voicing.
For more complete control of preamp distortion voicing, an additional EQ pedal can be placed after a distortion pedal; or, equivalently, the guitar amp's tone controls, after the built-in preamp distortion, can be used. An EQ pedal in the amp's effects loop, or the amp's tone controls placed after preamp distortion, constitutes post-distortion EQ, which finishes shaping the preamp distortion and sets up the power-tube distortion voicing.
As an example of pre-distortion EQ, Eddie Van Halen places a 6-band MXR EQ pedal before the Marshall amplifier head (pre-distortion EQ). Slash places a Boss GE-7, a 7-band EQ pedal, before his Marshall amp. This technique is similar to placing a Wah pedal before the amp's preamp distortion and leaving the Wah pedal positioned part-way down, sometimes mentioned as "fixed wah," (pre-distortion EQ), along with adjusting the amp's tone controls (post-distortion EQ).
If a dummy load guitar-amp configuration is used, an additional EQ position becomes available, between the dummy load and the final amplifier that drives the guitar speaker. Van Halen used an additional EQ in this position. This configuration is commonly used with rackmount systems.
Finally, an EQ pedal such as a 10-band graphic EQ pedal can be placed in the Insert jack of a mixer to replace the mixer channel's EQ controls, providing graphical control over the miked guitar speaker signal.
Equalization-related effects pedals include Wah, Auto-Wah, and Phase Shifter. Most EQ pedals also have an overall Level control distinct from the frequency-specific controls, thus enabling an EQ pedal to act as a configurable level-boost pedal. Some EQ pedals include:
- MXR M-108 10-band Equalizer
- BOSS GE-7 Equalizer
A wah-wah pedal is a moving bandpass filter whose frequency center is controlled by the musician via a rocker pedal. This filter boosts the frequencies in the instrument signal around the moving frequency center, allowing the musician to emphasize different areas of the frequency spectrum while playing. Rocked to the bass end of the spectrum, a wah-wah pedal makes a guitar signal sound hollow, without upper harmonics. On the other end of the sweep, the filter emphasizes higher-end harmonics and omits some of the low-end "growl" of the natural instrument sound. Rocking the pedal while holding a note creates a sound that goes from growl to shriek, and sounds like a crying baby, which is how the effect got its name and also the reason behind the Crybaby line of wah-wah pedals. The wah-wah pedal, used with guitar, is most associated with 1960s psychedelic rock and 1970s funk. During this period wah-wah pedals often incorporated a fuzzbox to process the sound before the wah-wah circuit, the combination producing a dramatic effect known as fuzz-wah.
Some wah-wah pedals include:
- Dunlop Cry Baby
- VOX V847 Wah Wah
- Danelectro Trip-L Wah
Auto-Wah / Envelope Filter
An Auto-Wah is a Wah-wah pedal without a rocker pedal, controlled instead by the dynamic envelope of the signal. An auto-wah, also called more technically an envelope filter, uses the level of the guitar signal to control the wah filter position, so that as a note is played, it automatically starts with the sound of a wah-wah pedal pulled back, and then quickly changes to the sound of a wah-wah pedal pushed forward, or the reverse movement depending on the settings. Controls include wah-wah pedal direction and input level sensitivity. This is an EQ-related effect and can be placed before preamp distortion or before power-tube distortion with natural sounding results. Auto-Wah pedals include:
- Electro-Harmonix Q-Tron
- MXR M-120 Auto Q
- Keeley Electronics Nova Wah
- Danelectro French Fries Auto-Wah
- Mu-Tron III
Early forms of the talk box, such as the Heil Talk Box, first appeared in Country Music circles in Nashville in the 1940',s 1950's, and 1960's, by artist like swing band pedal steel player Alvino Rey, Link Wray ("Rumble"), Bill West, a Country Music steel guitar player and husband of Dottie West, and Pete Drake, a Nashville mainstay on the pedal steel guitar and friend of Bill West. Drake used it on his 1964 album Forever, in what came to be called his "talking steel guitar." The device used the guitar amplifier's output to drive a speaker horn that pushed air into a tube held in the player's mouth, which filters and thereby shapes the sound leading to a unique effect. The singer and guitarist Peter Frampton made this effect famous with hit songs such as "Do You Feel Like We Do" and "Show Me the Way," as did Joe Walsh on "Rocky Mountain Way." On Van Halen's cover of "You Really Got Me" Eddie Van Halen uses a talk box after the guitar solo to make a sound similar to a person having sex. Newer devices, such as Danelectro's Free Speech pedal, use a microphone and vocoder-like circuit to modulate the frequency response of the guitar signal. Some Talk Boxes include: The Dunlop Heil Talk Box, Rocktron Banshee, and Peter Frampton's own company,Framptone.
A Volume pedal is a volume potentiometer that is tilted forward or back by foot. A volume pedal enables a musician to adjust the volume of their instrument while they are performing. Volume pedals can also be used to make the guitar's notes or chords fade in and out. This allows the percussive plucking of the strings to be softened or eliminated entirely, imparting a human-vocal sound. Volume pedals are also widely used with pedal steel guitars in country music. It has also been used to great effect in rock music; the Pat McGee Band's live version of "Can't Miss What You Never Had" on General Admission illustrates what the pedal is capable of. Some volume pedals are:
- Ernie Ball Stereo Volume Pedal
- Boss FV-50H Foot Volume
- VOX V850 Volume Pedal
Just as an Auto-Wah is a version of a Wah pedal controlled by the signal's dynamic envelope, there is an envelope-controlled version of a volume pedal. This is generally used to mimic automatically the sound of picking a note while the guitar's volume knob is turned down, then smoothly turning the knob up, for a violin-like muted attack. An example is:
- Boss SG-1 Slow Gear
Tremolo is a regular and repetitive variation in gain for the duration of a single note, which works like an auto-volume knob; this results in a swelling or fluttering sound. This effect is very popular in psychedelic and trip-hop music. The speed and depth of the flutter are usually user-controlled.This is a volume-related effects pedal. This effect is based on one of the earliest effects that were built into guitar amplifiers. Examples include:
- Demeter TRM-1 Tremulator
- Boss TR-2 Tremolo
- Electro-Harmonix Worm
- Line 6 Tap Tremolo
- Danelectro Cool-Cat Tremolo
A compressor acts as an automatic volume control, progressively decreasing the output level as the incoming signal gets louder, and vice versa. It preserves the note's attack rather than silencing it as with an Envelope Volume pedal. This adjustment of the volume for the attack and tail of a note evens out the overall volume of an instrument. Compressors can also change the behaviour of other effects, especially distortion. when applied toward the guitar, it can provide a uniformed sustained note; when applied to instruments with a normally short attack, such as drums or harpsichord, compression can drastically change the resulting sound. Another kind of compressor is the optical compressor which uses a light source (LED or lamp) to compress the signal.
Some compressor pedals are:
- Boss CS-3 Compression Sustainer
- MXR M-102 DynaComp
- Diamond Compressor (optical compressor)
- Line 6 Constrictor
- T-Rex Engineering's CompNova
- Electro-Harmonix Black Finger (optical compressor)
- Aphex Punch Factory Optical Compressor
- TC Electronic Hypergravity Compressor (parallel compressor)
A Delay or Echo pedal creates a copy of an incoming sound and slightly time-delays it, creating either a "slap" (single repetition) or an echo (multiple repetitions) effect. Delay pedals may use either analog or digital technology. Analog delays often are less flexible and not as "perfect" sounding as digital delays, but some guitarists argue that analog effects produce "warmer" tones. Early delay devices actually used magnetic tape to produce the time delay effect. U2's guitarist, The Edge, is known for his extensive use of delay effects. Some common Delay pedals are:
- Boss DD-6 Digital Delay
- Boss DD-20 Giga Delay
- Line 6 DL-4 Delay Modeler
- Line 6 Echo Park
- T-Rex Engineering's Replica
- TC Electronic Flashback Delay
- Danelectro FAB Echo
Another technology that is used in Delay units is a feedback circuit, consisting of a tracking oscillator circuit to hold a note of the last interval, and after amplifying the signal, send it back to the input side of the delay. While it was first associated with Boss DF-2 Super Feedbacker & Distortion, currently, the signal feedback circuit is employed by Delay pedals, and if used under "hold" mode (As in Boss DD-3) it will provide a sustain effect instead of a simply delay effect.
Extremely long delay times form a looping pedal, which allows performers to record a phrase or passage and play along with it. This allows a solo performer to record an accompaniment or ostinato passage and then, with the looping pedal playing back this passage, perform solo improvisations over the accompaniment. The guitarist creates the loop either on the spot or it is held in storage for later use (as in playback) when needed. Some examples of loops effects are:
- Boss RC-1 & RC-3 Loop Stations
- Boss RC-300 Loop Station
- DigiTech JamMan Looper
- Boomerang Looper
- TC Electronic Ditto
Reverb is the persistence of sound in a particular space after the original sound is removed. When sound is produced in a space, a large number of echoes build up and then slowly decay as the sound is absorbed by the walls and air, creating reverberation, or reverb. A plate reverb system uses an electromechanical transducer (actuator), similar to the driver in a loudspeaker, to create vibration in a plate of sheet metal. A pickup captures the vibrations as they bounce across the plate, and the result is output as an audio signal. A spring reverb system uses a transducer at one end of a spring and a pickup at the other, similar to those used in plate reverbs, to create and capture vibrations within a metal spring. Guitar amplifiers frequently incorporate spring reverbs due to their compact construction. Spring reverberators were once widely used in semi-professional recording due to their modest cost and small size. Due to quality problems and improved digital reverb units, spring reverberators are declining rapidly in use. Digital reverb units use various signal processing algorithms in order to create the reverb effect. Since reverberation is essentially caused by a very large number of echoes, simple DSPs use multiple feedback delay circuits to create a large, decaying series of echoes that die out over time.
Examples of reverb pedals include:
- DigiTech DigiDelay
- Electro-Harmonix Holy Grail
- Boss RV-5 Digital Reverb
- Line 6 Verbzilla
Before such effects are available electronically, these are accomplished by the use of Rotary speakers, by spinning the speakers and/or place a rotating baffle in front of it. This creates a doppler effect, and depend on the speed of the rotation, translate into phasing, flanging, chorus, vibrato, or even tremolo.
- Leslie Speakers: This is a unit that contains a bass speaker that blare into a rotating baffle, and a horn speaker that rotate like a siren. Originally designed for Hammond organs, they are also favored by guitarist; some say that no electronic effects can duplicate its sounds.
- Fender Vibratone: This is a simplified version of Leslie Speaker, containing only a 10" speaker that blare into a rotating baffle.
All the electronic-based effects can duplicate the sound of a rotating speakers, as all the following effects differ based on speed, volume, and modulation. In fact, it is not uncommon for a pedal to be capable of doing two or more of modulation effects.
Phase Shifter (Phaser)
A Phase Shifter creates a complex frequency response containing many regularly-spaced "notches" in an incoming signal by combining it with a copy of itself out of phase, and shifting the phase relationship cyclically. The phasing effect creates a "whooshing" sound that is reminiscent of the sound of a flying jet. This effect dominates the sound in the song Star Guitar by Chemical Brothers. The song was not played with any guitars but you can hear the phasing effect. The instrument being phased was actually a synthesizer. Some electronic "rotating speaker simulators" are actually phase shifters. Phase shifters were popular in the 1970s, particularly used with electric piano and funk bass guitar. The number of stages in a phase shifter is the number of moving dips in the frequency response curve. From a sonic perspective, this effect is equalization-oriented. However, it may be derived through moderate time-based processing. Some phaser pedals include:
- MXR M-101 Phase 90
- BOSS PH-3 Phase Shifter
- Electro-Harmonix Small Stone
- Moog] MF-103 12 Stage Phaser
- DigiTech Hyper Phase
A Vibe or Univibe pedal reproduces the sound of a rotating speaker by synchronizing volume oscillation, frequency-specific volume oscillation, vibrato (pitch wavering), phase shifting, and chorusing in relation to a non-rotating speaker. The modulation speed can be ramped up or down, with separate speeds for the bass and treble frequencies, to simulate the sound of a rotating bass speaker and a rotating horn. This effect is simultaneously a volume-oriented effect, an equalization-oriented effect, and a time-based effect. Furthermore, this effect is typically related to chorus. Some vibe pedals also include an overdrive effect, which allows the performer to add "tube"-style distortion. This effect is the most closely related to a rotary speaker. Some Vibe-only pedals include:
- BBE Soul Vibe
- Voodoo Lab Microvibe
Some vibe-chorus pedals include
- Dunlop Univibe
- Dunlop Rotovibe
- BBE Mind Bender
A vibrato pedal cyclically changes the pitch of the signal, giving the impression that the guitar is out of tune. The depth of the effect, the speed and the overall level of the effect can be controlled by potentiometers. Although similar in name and able to achieve similar sounds at high speed settings, a vibrato is different from a Vibe pedal.
Examples of vibrato-only pedals:
- TC Electronic Shaker Vibrato
- Malekko Omicron vibrato
- Subdecay Siren pitch vibrato
- Zvex Verter Instant LoFi Junky
- Boss VB-2w Vibrato
Some chorus and modulation pedals inclue a vibrato section that can be combined with chorus, vibe or rotary.
A Flanger simulates the sound effect originally created by momentarily slowing the tape during recording by holding something against the flange, or edge of the tape reel, and then allowing it to speed up again. This effect was used to simulate passing into "warp speed," in sci-fi films, and also in psychedelic rock music of the 1960s. Flanging has a sound similar to a phase-shifter, but different, yet is closely related to the production of chorus.
The first pedal-operated flanger designed for use as a guitar effect was designed by Jim Gamble of Tycobrahe Sound Company in Hermosa Beach, CA, during the mid 1970s. Last made in 1977, the existing "Pedalflangers" appear occasionally on eBay and sell for several hundred dollars. A modern "clone" of the Tycobrahe Pedalflanger is sold by Chicago Iron.Famous users of this Flanger effect include Randy Rhoads and Eddie Van Halen, coincidentally they both used the MXR M-117R flanger and Eddie Van Halen even has his own signature model now.
- Boss BF-3 Stereo Flanger
- Line 6 Liqua Flange
- MXR M-117R Flanger
- Danelectro FAB Flange
- Electro Harmonix Deluxe Electric Mistress
Chorus splits your guitars signal in two, then second signals pitch is then delayed and/or modulated in pitch and mixed back in with the dry signal. The effect sounds like several guitarists playing the same thing at the same time resulting in a wide swelling sound. Some common chorus pedals are:
- Boss CE-1 Chorus Ensemble (the original chorus effect pedal, and first device released by Boss)
- Boss CH-1 Super Chorus
- Electro-Harmonix Small Clone
- Ibanez CF-7 Chorus/Flanger
- Line 6 Space Chorus
- MXR M-134 Stereo Chorus
- TC Electronic Stereo Chorus /Flanger /Pitch Modulator
- Danelectro FAB Chorus
Rotary Speaker Simulator
Despite the numerous different analog devices, it is very rare for them to be able to duplicate all aspects of a Leslie speaker. Thus, Rotary Speaker Simulator are always going to be digital, utilizing modelling algorithms to model the relations between the rotating horns and bass baffle. And how the sound bounce around the cabinet. As Leslie also have an amplifier section, most of these typically have overdrives to simulate that aspect. Some of these pedals can even accept keyboard's input.
- Boss RT-20 Rotary Ensemble Pedal: This is one of the few pedals that is capable of modelling all aspect of a Leslie Speaker.
- Line 6 Rotomachine: Also a modelling pedal, it is available in a compact pedal size.
- DLS Roto-Sim: Hybrid of analog with DSP modelling.
Pitchshifters change the pitch of the note played via a user-specified amount. The range of pitch deviation depends on the equipment used, but many pedals are capable of raising and lowering the pitch two octaves above and below the fundamental pitch. The amount of pitch deviation can be set or controlled via a foot pedal (which typically offers smooth, continuous pitch control). Typically, such function will be used with the original signal, resulting in a Harmonizer: the pitch is altered and combined with the original pitch to create two or more note harmonies. These harmonies are typically programmed in discrete integer multiples of the fundamental tone. When used with an expression pedal, it provides a smooth, abeit slightly digital, bend-like effect. Pitch shifters can also be used to electronically "detune" the instrument. Some examples are:
- Digitech Whammy
- Boss PS-5 Super Shifter
- Electro Harmonix Harmonic Octave Generator
An Octaver mixes the input signal with a synthesised signal whose musical pitch is an octave lower or higher than the original. Effects that synthesize intervals besides octaves are referred to as harmonizers or pitch shifters. These are frequently used in bands without a bass player. Octave Up pedals include:
- Ampeg Scrambler
- Electro Harmonix POG (Polyphonic Octave Generator)
Octave Down pedals include:
- Boss OC-3 Super Octave
- Electro-Harmonix Octave Multiplexer
An Octave fuzz is a fuzz with an analog octave (up or down). The Octavia is one of the first octave pedals ever produced. Unlike octavers, the level of the octave cannot be controlled separately from the fuzz: increasing the gain makes the octave louder.
Octave up fuzzes include:
- Roger Mayer Octavia
- Chicago Iron Tycobrahe Octavia
- Catalinbread Octapussy
- Electro Harmonix Octavix
- Fender Blender
- Foxx Tone Machine
Octave down fuzzes include:
- MXR M-103 Blue Box
While audio feedback in general is undesirable due to the high frequency overtone, when controlled properly, it can provide true sustain of the sound (instead of using a distortion/compressor to make quiet notes louder, or a feedback of a signal in a circuit as in a delay unit). Several approaches have been used to produce guitar feedback effects, which sustain the sound from the guitar:
- The most primitive form, as used by Jimi Hendrix, is to use the feedback created when the guitar is played in front of a loudspeaker.
- The neck pickup is used as a driver to push the strings based on the bridge pickup, such as the Sustainiac Sustainer and Fernandes Sustainer.
- A string driver can be mounted on a stand as in the Vibesware Guitar Resonator, which is driven by the selected guitar pickup(s). Feedback start, stop and harmonics can be controlled here by positioning the drivers distance to the strings and the position along the guitar neck while playing.
- A signal amplifier that powers a headstock transducer, which in turn send feedback vibration down the string, as in Sustainiac's Model C.
- A handheld string driver can contain a pickup and driver, as in the EBow.
- A dedicated high-gain guitar amp can be used in the control room, without a microphone, as a footswitch-controlled string feedback driver. The microphone is placed on the speaker cabinet of the main guitar amp in the isolation booth or live room.
Switcher/Mixer (or "A/B" pedal)
A switcher pedal (also called an "A/B" pedal) enables players to run two effects or two effects chains in parallel, or switch between two effects with a single press of the pedal.
Some switcher pedals also incorporate a simple mixer, which allows mixing the dry guitar signal to be mixed with an effected signal. This is useful to make overly processed effects more mild and natural sounding. Examples of the use of the mixer function include:
- A wah can be mixed with dry guitar to make it more mild and full-bandwidth, with less volume swing.
- A compressor can be mixed with dry guitar to preserve the natural attack of the dry signal as well as the sustain of the compressor.
- Two overdrive pedals can be blended together.
- A strong phaser effect can be mixed with dry guitar to make it more subtle and musical.
Some examples of switcher pedals include:
- Dunlop A/B pedal
- Loop Master
Some examples of Switcher/mixer pedals include:
- BOSS LS-2 Line Selector
A noise gate allows a signal to pass through only when the signal's intensity is above a set threshold, which opens the gate. If the signal falls below the threshold, the gate closes, and no signal is allowed to pass. A noise gate can be used to control noise. When the level of the 'signal' is above the level of the 'noise', the threshold is set above the level of the 'noise' so that the gate is closed when there is no 'signal'. A noise gate does not remove noise from the signal: when the gate is open, both the signal and the noise will pass through.
Noise gates are also used as an effect to modify the envelope of signals, removing gradual attacks and decays.
Examples of noise gate pedals include:
- BOSS NS-2 Noise Suppressor
- MXR M-135 Smart Gate
There are three types of boosters.
- The first are signal boosters. These give a gain boost to the signal running through it and appear to make the guitar louder. They are known as clean boosts.
- The second are frequency boosters. These are similar to the signal boosters but instead of boosting the whole signal, they boost one specific frequency range. These include treble boosters.
- The third are harmonic boosters. These boost certain harmonics within the wave and can sometimes give a gritty, octave sound (in either direction)
A boost pedal can be used to make the guitar louder (set up last in the effect chain, often in the effects loop of a distorted amp), or to increase the gain of an overdriven amplifier. Before distortion, a booster only increases the saturation, not the volume.
Bass effects that condition the sound, rather than changing its character are called "sound conditioners." Gain booster effects pedals and bass preamplifier pedals increase the gain (or volume) of the bass guitar signal. Bass preamplifiers for double basses are designed to match the impedance of piezoelectric pickups with the input impedance of bass amplifiers. Some double bass preamplifiers may also provide phantom power for powering condenser microphones and anti-feedback features such as a notch filter (see "Filter-based effects" section below).
Volume pedals are volume potientiometers set into a rocking foot treadle, so that the volume of the bass guitar can be changed by the foot. Compression pedals affect the dynamics (volume levels) of a bass signal by subtly increasing the volume of quiet notes and reducing the volume of loud notes, which smooths out or "compresses" the overall sound. Limiters, which are similar to compressors, prevent the upper volume levels (peaks) of notes from getting too loud, which can damage speakers. Noise gates remove hums and hisses that occur with distortion pedals, vintage pedals, and some electric basses.
Bass distortion effects preamplify the signal until the signals' waveform "clips" and becomes distorted, giving a "growling", "fuzzy" or "buzzing" sound. Until the late 1980s, distortion effects designed specifically for electric bass' low range were not commonly available in stores, so most electric bass players who wanted a distortion effect either used the natural overdrive that is produced by setting the preamplifier gain to very high settings or used an electric guitar distortion pedal. Using the natural overdrive from an amplifier's preamplifier or a guitar distortion effect has the side effect of removing the bass' low range (low-pitched) sounds. When a low-range note is amplified to the point of "clipping", the note tends to go up an octave to its second harmonic, making deep bass notes sound "tinny".
In the 1990s and 2000s, bass distortion effects became widely available. These effects contained circuitry which ensured that the low-range bass signal was maintained in the distorted bass tone. Bass distortion is used in genres such as metal, thrash, hardcore, and punk.
Bass "overdrive" effects use a vacuum tube (or digitally-simulated tube modelling techniques) to compress the top of the signal's wave form, giving a smoother distorted signal than regular distortion effects. Regular bass distortion effects preamplify the signal to the point that it develops a gritty or "dirty" tone.
Fuzz bass effects are sometimes created for bass by using fuzzbox effects designed for electric guitars. Fuzzboxes boost and clip the signal sufficiently to turn a standard sine wave input into what is effectively a square wave output, giving a much more distorted and synthetic sound than a standard distortion or overdrive. Paul McCartney of The Beatles used fuzz bass on "Think for Yourself" in the 1966 album "Rubber Soul"
Filtered based effects
Filter based effects for bass include equalizer, phase shifter, wah and auto-wah.
A bass equalizer is the most commonly used of these three effects. It adjusts the frequency response in a number of different frequency bands. While its function is similar to a tone controls on an amplifier, such as rudimentary "bass" and "treble" frequency knobs, it allows for more precise frequency changes. A rack-mounted bass equalizer, for example, may have ten sliders to control the frequency range encompassed by a regular "bass" frequency knob.
In comparison with an electric guitar equalizer, a bass equalizer usually has a lower frequency range that goes down to 40 Hz, to accommodate the electric bass' lower range. Some bass equalizers designed for use with extended range basses go even lower, to 20 Hz. Equalizers can be used to change the tone and sound of the electric bass. If the instrument sounds too "boomy", the bassist can lower the frequency which is overly resonant, or if there is too much fingernail or pick noise, the higher frequencies can be reduced.
Notch filters (also called band-stop filters or band-rejection filters) are sometimes used with double basses. Notch filters are filters that allow most frequencies to pass through unaltered, while attenuating those in a specific range to very low levels. Notch filters are used in instrument amplifiers and preamplifiers for acoustic instruments such as acoustic guitar, mandolin, and bass instrument amplifiers to reduce or prevent feedback. While most notch filters are set manually by the user, there are also automatic notch filters which detect the onset of feedback and notch out the frequency before damaging feedback begins.
Bass Phase Shifters create a complex frequency response containing many regularly-spaced "notches" in an incoming signal by combining it with a copy of itself out of phase, and shifting the phase relationship cyclically. The phasing effect creates a "whooshing" sound that is reminiscent of the sound of a flying jet.
Bass chorus effects use a cycling, variable delay time that is short so that individual repetitions are not heard. The result is a thick, "swirling" sound that suggests multiple instruments playing in unison (chorus) that are slightly out of tune. Bass chorus effects were more common in the late 1980s, when manufacturers such as Peavey included chorus effects in its bass amplifiers. In the 1990s and 2000s, more sophisticated bass chorus effects devices were created which only apply the swirling chorus effect to the higher parts of the bass tone, leaving the instrument's low fundamental untouched.
A multi-FX unit is a single effects device that can perform several guitar effects simultaneously. Such devices generally use digital processing to simulate many of the above-mentioned effects without the need to carry several single-purpose units. In addition to the classic effects, most have amplifier/speaker simulations not found in analog units. This allows a guitarist to play directly into a recording device while simulating an amplifier and speaker of his choice.
A typical digital multi-effects pedal is programmed, with several memory locations available to save custom user settings. Many lack the front-panel knobs of analog devices, using buttons instead to program various effect parameters. Multi-effects devices continue to evolve, some gaining MIDI or USB interfaces to aid in programming. Examples include:
- Tech 21 Sans Amp - A line of analog effects with distortion and speaker simulation capability.
- Line 6 POD XT Live
- Behringer V-Amp Pro
- DigiTech RP series
- DigiTech GNX series
- Boss ME-20, ME-50, GT-6, GT-8
- Zoom G2, G3, G5 series
- Vox Tonelab series
- Roland VG series
- Korg AX series
The quality of sound that is a major feature of separate pedals can never be matched by a multi-effects unit but they are ideal for a guitarist on a budget.