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An electric guitar is a fretted stringed instrument with a neck and body that uses a pickup to convert the vibration of its strings into electrical signals. The vibration occurs when a guitarist strums, plucks or fingerpicks the strings. It is sensed by a pickup, most commonly by a magnetic pickup that uses the principle of direct electromagnetic induction. The signal generated by an electric guitar is too weak to drive a loudspeaker, so it is plugged into a guitar amplifier before being sent to a loudspeaker, which makes a sound loud enough to hear. The output of an electric guitar is an electric signal, and the signal can easily be altered by electronic circuits to add "color" to the sound or change the sound. Often the signal is modified using effects such as reverb and distortion and "overdrive", with the growling sound of the latter being a key element of the sound of the electric guitar as it is used in blues and rock music.
Invented in 1931, the amplified electric guitar was adopted by jazz guitarists, who sought to be able to do single-note guitar solos in large big band ensembles. Early proponents of the electric guitar on record included Les Paul, Lonnie Johnson, Sister Rosetta Tharpe, T-Bone Walker, and Charlie Christian. During the 1950s and 1960s, the electric guitar became the most important instrument in pop music. It has evolved into an instrument that is capable of a multitude of sounds and styles in genres ranging from pop and rock to country music, blues and jazz. It served as a major component in the development of electric blues, rock and roll, rock music, heavy metal music and many other genres of music.
Electric guitar design and construction vary greatly in the shape of the body and the configuration of the neck, bridge, and pickups. Guitars may have a fixed bridge or a spring-loaded hinged bridge that lets players "bend" the pitch of notes or chords up or down or perform vibrato effects. The sound of a guitar can be modified by new playing techniques such as string bending, tapping, hammering on, using audio feedback, or slide guitar playing. There are several types of electric guitar, including the solid-body guitar, various types of hollow-body guitars, the six-string guitar (the most common type, usually tuned E, A, D, G, B, E, from lowest to highest strings), the seven-string guitar, which typically adds a low B string below the low E, and the twelve-string electric guitar, which has six pairs of strings.
Popular music and rock groups often use the electric guitar in two roles: as a rhythm guitar, which plays the chord sequence or progression and riffs and sets the beat (as part of a rhythm section), and as a lead guitar, which is used to perform instrumental melody lines, melodic instrumental fill passages, and solos. In a small group, such as a power trio, one guitarist switches between both roles. In larger rock and metal bands, there is often a rhythm guitarist and a lead guitarist.
Many experiments at electrically amplifying the vibrations of a string instrument were made dating back to the early part of the 20th century. Patents from the 1910s show telephone transmitters were adapted and placed inside violins and banjos to amplify the sound. Hobbyists in the 1920s used carbon button microphones attached to the bridge; however, these detected vibration from the bridge on top of the instrument, resulting in a weak signal. With numerous people experimenting with electrical instruments in the 1920s and early 1930s, there are many claimants to have been the first to invent an electric guitar.
The "Frying Pan", 1932
Electric guitars were originally designed by acoustic guitar makers and instrument manufacturers. Some of the earliest electric guitars adapted hollow-bodied acoustic instruments and used tungsten pickups. The first electrically amplified guitar was designed in 1931 by George Beauchamp, the general manager of the National Guitar Corporation, with Paul Barth, who was vice president. The maple body prototype for the one-piece cast aluminium "frying pan" was built by Harry Watson, factory superintendent of the National Guitar Corporation. Commercial production began in late summer of 1932 by the Ro-Pat-In Corporation (Electro-Patent-Instrument Company), in Los Angeles, a partnership of Beauchamp, Adolph Rickenbacker (originally Rickenbacher), and Paul Barth. In 1934, the company was renamed the Rickenbacker Electro Stringed Instrument Company. In that year Beauchamp applied for a United States patent for an Electrical Stringed Musical Instrument and the patent was issued in 1937.
By early-mid 1935, Electro String Instrument Corporation had achieved mainstream success with the A-22 Frying Pan, and set out to capture a new audience through its release of the "Electro-Spanish Model B" and the "Electro-Spanish Ken Roberts" which was the first full 25" scale electric guitar produced. The Electro-Spanish Ken Roberts provided players a full 25" scale, with 17 frets free of the fretboard. It is estimated that fewer than 50 Electro-Spanish Ken Roberts were constructed between 1933 and 1937; fewer than 10 are known to survive today.
The need for the amplified guitar became apparent during the big band era as orchestras increased in size, particularly when acoustic guitars had to compete with large, loud brass sections. The first electric guitars used in jazz were hollow archtop acoustic guitar bodies with electromagnetic transducers. Early electric guitar manufacturers include Rickenbacker in 1932; Dobro in 1933; National, AudioVox and Volu-tone in 1934; Vega, Epiphone (Electrophone and Electar), and Gibson in 1935 and many others by 1936.
Fender Stratocaster is one of the most often emulated electric guitar shapes
The solid-body electric guitar is made of solid wood, without functionally resonating air spaces. The first solid-body Spanish standard guitar was offered by Vivi-Tone no later than 1934. This model featured a guitar-shaped body of a single sheet of plywood affixed to a wood frame. Another early, substantially solid Spanish electric guitar, called the Electro Spanish, was marketed by the Rickenbacker guitar company in 1935 and made of Bakelite. By 1936, the Slingerland company introduced a wooden solid-body electric model, the Slingerland Songster 401 (and a lap steel counterpart, the Songster 400).
The earliest documented performance with an electrically amplified guitar was in 1932, by Gage Brewer, a musician based in Wichita, Kansas. He had an Electric Hawaiian A-25 (frypan, lap steel) and a standard Electric Spanish from George Beauchamp of Los Angeles. Brewer publicized his new instruments in an article in the Wichita Beacon of 2 October 1932 and through performances that month. The first recordings using the electric guitar were by Hawaiian-style players, in 1933. Bob Dunn of Milton Brown's Musical Brownies introduced the electric Hawaiian guitar to Western swing with his January 1935 Decca recordings, departing almost entirely from the Hawaiian musical influence and heading towards jazz and blues. Alvino Rey was an artist who took this instrument to a wide audience in a large orchestral setting and later developed the pedal steel guitar for Gibson. An early proponent of the electric Spanish guitar was jazz guitarist George Barnes, who used the instrument in two songs recorded in Chicago on 1 March 1938, "Sweetheart Land" and "It's a Low-Down Dirty Shame". Some incorrectly attribute the first recording to Eddie Durham, but his recording with the Kansas City Five was made 15 days later. Durham introduced the instrument to a young Charlie Christian, who made the instrument famous in his brief life and would be a major influence on jazz guitarists for decades thereafter.
Gibson's first production electric guitar, marketed in 1936, was the ES-150 model ("ES" for "Electric Spanish", and "150" reflecting the $150 price of the instrument, along with matching amplifier). The ES-150 guitar featured a single-coil, hexagonally shaped "bar" pickup, which was designed by Walt Fuller. It became known as the "Charlie Christian" pickup (named for the great jazz guitarist who was among the first to perform with the ES-150 guitar). The ES-150 achieved some popularity but suffered from unequal loudness across the six strings.
Early proponents of the electric guitar on record include Alvino Rey (Phil Spitalney Orchestra), Les Paul (Fred Waring Orchestra), Danny Stewart (Andy Iona Orchestra), George Barnes (under many aliases), Lonnie Johnson, Floyd Smith, Big Bill Broonzy, T-Bone Walker, George Van Eps, Charlie Christian (Benny Goodman Orchestra), Tampa Red, Memphis Minnie, and Arthur Crudup.
A functionally solid-body electric guitar was designed and built in 1940 by Les Paul from an Epiphone acoustic archtop. His "log guitar" (so called because it consisted of a simple 4x4 wood post with a neck attached to it and homemade pickups and hardware, with two detachable Epiphone hollow-body halves attached to the sides for appearance only) shares nothing in design or hardware with the solid-body Gibson Les Paul introduced in 1952. However, the feedback associated with hollow-bodied electric guitars was understood long before Paul's "log" was created in 1940; Gage Brewer's Ro-Pat-In of 1932 had a top so heavily reinforced that it essentially functioned as a solid-body instrument. In 1945, Richard D. Bourgerie made an electric guitar pickup and amplifier for professional guitar player George Barnes. Bourgerie worked through World War II at Howard Radio Company, making electronic equipment for the American military. Barnes showed the result to Les Paul, who then arranged for Bourgerie to have one made for him.
This table shows the layout of pitches on a standard tuning six-string guitar, which is tuned E, A, D, G, B, E, going from the lowest-pitch, thickest string to the highest - pitch, thinnest string. The table depicts a guitar fretboard as it would appear to an observer looking at a guitar that is on its side and upside-down, thus giving the table the same appearance that a guitarist would see when holding the instrument in playing position. Zero is the nut; 5 is the fifth (tuning) fret. This table only shows up to the twelfth fret. Most electric guitars have additional frets beyond the twelfth fret which have the same layout as the 1st- 12th fret (although the notes are an octave higher in pitch).
1.1 machine heads
1.2 truss rod cover
1.3 string guide
2.2 inlay fret markers
2.4 neck joint
3.1 "neck" pickup
3.2 "bridge" pickup
3.5 fine tuners and tailpiece assembly
3.6 whammy bar (vibrato arm)
3.7 pickup selector switch
3.8 volume and tone control knobs
3.9 output connector (output jack)(TS)
3.10 strap buttons
4.1 bass strings
4.2 treble strings
Electric guitar design and construction vary greatly in the shape of the body and the configuration of the neck, bridge, and pickups. However, some features are present on most guitars. The photo below shows the different parts of an electric guitar. The headstock (1) contains the metal machine heads (1.1), which use a worm gear for tuning. The nut (1.4)—a thin fret-like strip of metal, plastic, graphite or bone—supports the strings at the headstock end of the instrument. The frets (2.3) are thin metal strips that stop the string at the correct pitch when the player pushes a string against the fingerboard. The truss rod (1.2) is a metal rod (usually adjustable) that counters the tension of the strings to keep the neck straight. Position markers (2.2) provide the player with a reference to the playing position on the fingerboard.
The neck and fretboard (2.1) extend from the body. At the neck joint (2.4), the neck is either glued or bolted to the body. The body (3) is typically made of wood with a hard, polymerized finish. Strings vibrating in the magnetic field of the pickups (3.1, 3.2) produce an electric current in the pickup winding that passes through the tone and volume controls (3.8) to the output jack. Some guitars have piezo pickups, in addition to or instead of magnetic pickups.
Some guitars have a fixed bridge (3.4). Others have a spring-loaded hinged bridge called a vibrato bar, tremolo bar, or whammy bar, which lets players bend notes or chords up or down in pitch or perform a vibrato embellishment. A plastic pickguard on some guitars protects the body from scratches or covers the control cavity, which holds most of the wiring. The degree to which the choice of woods and other materials in the solid-guitar body (3) affects the sonic character of the amplified signal is disputed. Many believe it is highly significant, while others think the difference between woods is subtle. In acoustic and archtop guitars, wood choices more clearly affect tone.
Woods typically used in solid-body electric guitars include alder (brighter, but well rounded), swamp ash (similar to alder, but with more pronounced highs and lows), mahogany (dark, bassy, warm), poplar (similar to alder), and basswood (very neutral). Maple, a very bright tonewood, is also a popular body wood, but is very heavy. For this reason it is often placed as a "cap" on a guitar made primarily of another wood. Cheaper guitars are often made of cheaper woods, such as plywood, pine or agathis—not true hardwoods—which can affect durability and tone. Though most guitars are made of wood, any material may be used. Materials such as plastic, metal, and even cardboard have been used in some instruments.
The guitar output jack typically provides a monaural signal. Many guitars with active electronics use a jack with an extra contact normally used for stereo. These guitars use the extra contact to break the ground connection to the on-board battery to preserve battery life when the guitar is unplugged. These guitars require a mono plug to close the internal switch and connect the battery to ground. Standard guitar cables use a high-impedance 1/4-inch (6.35-mm) mono plug. These have a tip and sleeve configuration referred to as a TS phone connector. The voltage is usually around 1 to 9 millivolts.
A few guitars feature stereo output, such as Rickenbacker guitars equipped with Rick-O-Sound. There are a variety of ways the "stereo" effect may be implemented. Commonly, but not exclusively, stereo guitars route the neck and bridge pickups to separate output buses on the guitar. A stereo cable then routes each pickup to its own signal chain or amplifier. For these applications, the most popular connector is a high-impedance 1/4-inch plug with a tip, ring and sleeve configuration, also known as a TRS phone connector. Some studio instruments, notably certain Gibson Les Paul models, incorporate a low-impedance three-pin XLR connector for balanced audio. Many exotic arrangements and connectors exist that support features such as midi and hexaphonic pickups.
The bridge and tailpiece, while serving separate purposes, work closely together to affect playing style and tone. There are four basic types of bridge and tailpiece systems on electric guitars. Within these four types are many variants.
A hard-tail guitar bridge anchors the strings at or directly behind the bridge and is fastened securely to the top of the instrument. These are common on carved-top guitars, such as the Gibson Les Paul and the Paul Reed Smith models, and on slab-body guitars, such as the Music Man Albert Lee and Fender guitars that are not equipped with a vibrato arm.
A floating or trapeze tailpiece (similar to a violin's) fastens to the body at the base of the guitar. These appear on Rickenbackers, Gretsches, Epiphones, a wide variety of archtop guitars, particularly Jazz guitars, and the 1952 Gibson Les Paul.
Pictured is a tremolo arm or vibrato tailpiece style bridge and tailpiece system, often called a whammy bar or trem. It uses a lever ("vibrato arm") attached to the bridge that can temporarily slacken or tighten the strings to alter the pitch. A player can use this to create a vibrato or a portamento effect. Early vibrato systems were often unreliable and made the guitar go out of tune easily. They also had a limited pitch range. Later Fender designs were better, but Fender held the patent on these, so other companies used older designs for many years.
Detail of a Squier-made Fender Stratocaster. Note the vibrato arm, the 3 single-coil pickups, the volume and tone knobs.
With expiration of the Fender patent on the Stratocaster-style vibrato, various improvements on this type of internal, multi-spring vibrato system are now available. Floyd Rose introduced one of the first improvements on the vibrato system in many years when, in the late 1970s, he experimented with "locking" nuts and bridges that prevent the guitar from losing tuning, even under heavy vibrato bar use.
Tune-o-matic with "strings through the body" construction (without stopbar)
The fourth type of system employs string-through body anchoring. The strings pass over the bridge saddles, then through holes through the top of the guitar body to the back. The strings are typically anchored in place at the back of the guitar by metal ferrules. Many believe this design improves a guitar's sustain and timbre. A few examples of string-through body guitars are the Fender Telecaster Thinline, the Fender Telecaster Deluxe, the B.C. Rich IT Warlock and Mockingbird, and the Schecter Omen 6 and 7 series.
Main article: Pickup (music technology)
Compared to an acoustic guitar, which has a hollow body, electric guitars make much less audible sound when their strings are plucked, so electric guitars are normally plugged into a guitar amplifier and speaker. When an electric guitar is played, string movement produces a signal by generating (i.e., inducing) a small electric current in the magnetic pickups, which are magnets wound with coils of very fine wire. The signal passes through the tone and volume circuits to the output jack, and through a cable to an amplifier. The current induced is proportional to such factors as string density and the amount of movement over the pickups.
Pickups on a Fender Squier "Fat Strat" guitar—a "humbucker" pickup on the left and two single-coil pickups on the right.
Because in most cases it is desirable to isolate coil-wound pickups from the unintended sound of internal vibration of loose coil windings, a guitar's magnetic pickups are normally embedded or "potted" in wax, lacquer, or epoxy to prevent the pickup from producing a microphonic effect. Because of their natural inductive qualities, all magnetic pickups tend to pick up ambient, usually unwanted electromagnetic interference or EMI. The resulting hum is particularly strong with single-coil pickups, and it is aggravated by the fact that many vintage guitars are insufficiently shielded against electromagnetic interference. The most common source is 50- or 60-Hz hum from power transmission systems (house wiring, etc.). Since nearly all amplifiers and audio equipment associated with electric guitars must be plugged in, it is a continuing technical challenge to reduce or eliminate unwanted hum.
Double-coil or "humbucker" pickups were invented as a way to reduce or counter the unwanted ambient hum sounds (known as 60-cycle hum). Humbuckers have two coils of opposite magnetic and electric polarity to produce a differential signal. Electromagnetic noise that hits both coils equally tries to drive the pickup signal toward positive on one coil and toward negative on the other, which cancels out the noise. The two coils are wired in phase, so their signal adds together. This high combined inductance of the two coils leads to the richer, "fatter" tone associated with humbucking pickups.
Piezoelectric pickups use a "sandwich" of quartz crystal or other piezoelectric material, typically placed beneath the string saddles or nut. These devices respond to pressure changes from all vibration at these specific points.
Optical pickups are a type of pickup that sense string and body vibrations using infrared LED light. These pickups are not sensitive to EMI.
Some "hybrid" electric guitars are equipped with additional microphone, piezoelectric, optical, or other types of transducers to approximate an acoustic instrument tone and broaden the sonic palette of the instrument.
Electric guitar necks vary in composition and shape. The primary metric of guitar necks is the scale length, which is the vibrating length of the strings from nut to bridge. A typical Fender guitar uses a 25.5-inch scale length, while Gibson uses a 24.75-inch scale length in their Les Paul. While the scale length of the Les Paul is often described as 24.75 inches, it has varied through the years by as much as a half inch.
Frets are positioned proportionally to scale length—the shorter the scale length, the closer the fret spacing. Opinions vary regarding the effect of scale length on tone and feel. Popular opinion holds that longer scale length contributes to greater amplitude. Reports of playing feel are greatly complicated by the many factors involved in this perception. String gauge and design, neck construction and relief, guitar setup, playing style and other factors contribute to the subjective impression of playability or feel.
A bolt-on neck
Necks are described as bolt-on, set-in, or neck-through, depending on how they attach to the body. Set-in necks are glued to the body in the factory. They are said to have a warmer tone and greater sustain. This is the traditional type of joint. Leo Fender pioneered bolt-on necks on electric guitars to facilitate easy adjustment and replacement. Neck-through instruments extend the neck the length of the instrument, so that it forms the center of the body, and are known for long sustain and for being particularly sturdy. While a set-in neck can be carefully unglued by a skilled luthier, and a bolt-on neck can simply be unscrewed, a neck-through design is difficult or even impossible to repair, depending on the damage. Historically, the bolt-on style has been more popular for ease of installation and adjustment. Since bolt-on necks can be easily removed, there is an after-market in replacement bolt-on necks from companies such as Warmoth and Mighty Mite. Some instruments—notably most Gibson models—continue to use set-in glued necks. Neck-through bodies are somewhat more common in bass guitars.
Materials for necks are selected for dimensional stability and rigidity, and some allege that they influence tone. Hardwoods are preferred, with maple, mahogany, and ash topping the list. The neck and fingerboard can be made from different materials; for example, a guitar may have a maple neck with a rosewood or ebony fingerboard. In the 1970s, designers began to use exotic man-made materials such as aircraft-grade aluminum, carbon fiber, and ebonol. Makers known for these unusual materials include John Veleno, Travis Bean, Geoff Gould, and Alembic.
Aside from possible engineering advantages, some feel that in relation to the rising cost of rare tonewoods, man-made materials may be economically preferable and more ecologically sensitive. However, wood remains popular in production instruments, though sometimes in conjunction with new materials. Vigier guitars, for example, use a wooden neck reinforced by embedding a light, carbon fiber rod in place of the usual heavier steel bar or adjustable steel truss rod. After-market necks made entirely from carbon fiber fit existing bolt-on instruments. Few, if any, extensive formal investigations have been widely published that confirm or refute claims over the effects of different woods or materials on electric guitar sound.
A neck-through bass guitar
Several neck shapes appear on guitars, including shapes known as C necks, U necks, and V necks. These refer to the cross-sectional shape of the neck (especially near the nut). Several sizes of fret wire are available, with traditional players often preferring thin frets, and metal shredders liking thick frets. Thin frets are considered better for playing chords, while thick frets allow lead guitarists to bend notes with less effort.
An electric guitar with a folding neck called the "Foldaxe" was designed and built for Chet Atkins by Roger C. Field.Steinberger guitars developed a line of exotic, carbon fiber instruments without headstocks, with tuning done on the bridge instead.
Fingerboards vary as much as necks. The fingerboard surface usually has a cross-sectional radius that is optimized to accommodate finger movement for different playing techniques. Fingerboard radius typically ranges from nearly flat (a very large radius) to radically arched (a small radius). The vintage Fender Telecaster, for example, has a typical small radius of approximately 7.25 inches. Some manufacturers have experimented with fret profile and material, fret layout, number of frets, and modifications of the fingerboard surface for various reasons. Some innovations were intended to improve playability by ergonomic means, such as Warmoth Guitars' compound radius fingerboard. Scalloped fingerboards added enhanced microtonality during fast legato runs. Fanned frets intend to provide each string with an optimal playing tension and enhanced musicality. Some guitars have no frets—and others, like the Gittler guitar, have no neck in the traditional sense.
While an acoustic guitar's sound depends largely on the vibration of the guitar's body and the air inside it, the sound of an electric guitar depends largely on the signal from the pickups. The signal can be "shaped" on its path to the amplifier via a range of effect devices or circuits that modify the tone and characteristics of the signal. Amplifiers and speakers also add coloration to the final sound.
Electric guitars usually have one to four magnetic pickups. Identical pickups produce different tones depending on how near they are to the neck or bridge. Bridge pickups produce a bright or trebly timbre, and neck pickups are warmer or more bassy. The type of pickup also affects tone. Dual-coil pickups sound warm, thick, perhaps even muddy; single-coil pickups sound clear, bright, perhaps even biting. Guitars don't require a uniform pickup type: a common mixture is the "fat Strat" arrangement of one dual-coil at the bridge position and single coils in the middle and neck positions, known as HSS (humbucker/single/single). Some guitars have piezoelectric pickup in addition to electromagnetic pickups. Piezo pickups produce a more acoustic sound. The piezo runs through a built-in equalizer (EQ) to improve similitude and control tone. A blend knob controls the mix between electromagnetic and piezoelectric sounds.
Where there is more than one pickup, a pickup selector switch is usually present. These typically select or combine the outputs of two or more pickups, so that two-pickup guitars have three-way switches, and three-pickup guitars have five-way switches (a Gibson Les Paul three-pickup Black Beauty has a three-position toggle switch which configures bridge, bridge and middle [switch in middle position] and neck pickups). Further circuitry sometimes combines pickups in different ways. For instance, phase switching places one pickup out of phase with the other(s), leading to a "honky", "nasal", or "funky" sound. Individual pickups can also have their timbre altered by switches, typically coil tap switches that effectively short-circuit some of a dual-coil pickup's windings to produce a tone similar to a single-coil pickup (usually done with push-pull volume knobs).
The final stages of on-board sound-shaping circuitry are the volume control (potentiometer) and tone control (which "rolls off" the treble frequencies). Where there are individual volume controls for different pickups, and where pickup signals can be combined, they would affect the timbre of the final sound by adjusting the balance between pickups from a straight 50:50.
The strings fitted to the guitar also have an influence on tone. Rock musicians often prefer the lightest gauge of roundwound string, which is easier to bend, while jazz musicians go for heavier, flatwound strings, which have a rich, dark sound. Steel, nickel, and cobalt are common string materials, and each gives a slightly different tone color. Recent guitar designs may incorporate much more complex circuitry than described above; see Digital and synthesizer guitars, below.
A Fender Bassman amp head with a 15" speaker cabinet. Main article: Guitar amplifier
The solid-body electric guitar does not produce enough sound to be audible to the audience in a performance setting without it being plugged into an electronic amplifier (exceptions would be when a guitarist is doing a sound recording and plugs into the mixing console or when a bassist plugs directly into the PA system in a live show).
Guitar amplifiers are designed with a different approach than that used to design sound reinforcement system power amplifiers and home "hi-fi" stereo systems. Audio amplifiers generally are intended to accurately reproduce the source signal without adding unwanted tonal coloration (i.e., they have a flat frequency response) or unwanted distortion. In contrast, most guitar amplifiers are intended to provide tonal coloration and/or overdrive (distortion of various types) that can add to a guitar signal. A common tonal coloration sought by guitarists is rolling off some of the high frequencies. Along with a guitarist's playing style and choice of electric guitar and pickups, the choice of guitar amp model is a key part of a guitarist's unique tone. Many top guitarists are associated with a specific brand of guitar amp. As well, electric guitarists in blues, rock and many related sub-genres often intentionally choose amplifiers or effects units with controls that distort or alter the sound (to a greater or lesser degree).
In the 1950s and 1960s, some guitarists began exploring a wider range of tonal effects by distorting the sound of the instrument. To do this, they used overdrive — increasing the gain of the preamplifier beyond the level where the signal could be reproduced with little distortion, resulting in a "fuzzy" sound. This effect is called "clipping" by sound engineers, because when viewed with an oscilloscope, the wave forms of a distorted signal appear to have had their peaks "clipped off", in the process introducing additional tones (often approximating the harmonics characteristic of a square wave of that basic frequency). This was not actually a new development in the musical instrument or its supporting gear, but rather a shift of aesthetics, such sounds not having been thought desirable previously. Some distortion modes with an electric guitar increase the sustain of single notes and chords, which changes the sound of the instrument. In particular, distortion made it more feasible to perform guitar solos that used long, sustained notes.
After distortion became popular amongst rock music groups, guitar amplifier manufacturers included various provisions for it as part of amplifier design, making amps easier to overdrive, and providing separate "dirty" and "clean" channels so that distortion could easily be switched on and off. The distortion characteristics of vacuum tube amplifiers are particularly sought-after in blues and many rock music genres, and various attempts have been made to emulate them without the disadvantages (e.g., fragility, low power, expense) of actual tubes. Distortion, especially in tube based amplifiers, can come from several sources: power supply sag as more power is demanded than the supply can provide at a steady voltage, deliberate gain over drive of active elements, or alterations in the feedback provisions for various circuit stages.
Guitar amplifiers have long included at least a few effect units, often tone controls for bass and treble, an integrated tremolo system (sometimes incorrectly labeled (and marketed) as vibrato), and/or a mechanical spring reverb unit. In the 2010s, guitar amps often have onboard distortion effects. Some 2010-era amps provide multiple effects, such as chorus, flanger, phaser and octave down effects. The use of offboard effects such as stompbox pedals is made possible by either plugging the guitar into the external effect pedal and then plugging the effect pedal into the amp, or by using one or more effects loops, an arrangement that allows effects to be electrically or mechanically switched in or out of the signal path as desired. In the signal chain, the effects loop is typically located between the preamplifier stage and the power amplifier stages (though reverb units generally precede the effects loop if both are featured on an amplifier). This allows the guitarist to apply modulation effects to the signal after it has been processed through the preamplifier, something generally desirable, particularly with time-based effects such as delay. By the 2010s, guitar amplifiers usually included a distortion effect. Effects circuitry (whether internal to an amplifier or not) can be taken as far as amp modeling, by which is meant alteration of the electrical and audible behavior in such a way as to make an amp sound as though it were another (or one of several) amplifiers. When done well, a solid state amplifier can sound like a tube amplifier (even one with power supply sag), reducing the need to manage more than one amp. Some modeling systems even attempt to emulate the sound of different speakers/cabinets. Nearly all amp and speaker cabinet modeling is done digitally, using computer techniques (e.g., Digital Signal Processing or DSP circuitry and software). There is disagreement about whether this approach is musically satisfactory, and also whether this or that unit is more or less successful than another.
Main article: Effects unit A Boss distortion pedal in use
In the 1960s, the tonal palette of the electric guitar was further modified by introducing effect units in its signal path, before the guitar amp, of which one of the earliest units was the fuzz pedal. Effects units come in several formats, the most common of which are the stompbox "pedal" and the rackmount unit. A stomp box (or pedal) is a small metal or plastic box containing the circuitry, which is placed on the floor in front of the musician and connected in line with the patch cord connected to the instrument. The box is typically controlled by one or more foot-pedal on-off switches and it typically contains only one or two effects. Pedals are smaller than rackmount effects and usually less expensive. "Guitar pedalboards" are used by musicians who use multiple stomp-boxes; these may be a DIY project made with plywood or a commercial stock or custom-made pedalboard.
A rackmount effects unit may contain an electronic circuit nearly identical to a stompbox-based effect, but it is mounted in a standard 19" equipment rack, which is usually mounted in a road case that is designed to protect the equipment during transport. More recently, as signal-processing technology continuously becomes more feature-dense, rack-mount effects units frequently contain several types of effects. They are typically controlled by knobs or switches on the front panel, and often by a MIDI digital control interface.
Typical effects include:
In the 1970s, as effects pedals proliferated, their sounds were combined with tube amp distortion at lower, more controlled volumes by using power attenuators, such as Tom Scholz's Power Soak, as well as re-amplified dummy loads, such as Eddie Van Halen's use of dummy-load power resistor, post-power-tube effects, and a final solid-state amp driving the guitar speakers.
Recent amplifiers may include digital technology similar to modern effects pedals, including the ability to model or emulate a variety of classic amps.
The Zoom 505 multi-effect pedal
A multi-effects device (also called a "multi-FX" device) is a single electronics effects pedal or rack-mount device that contains many electronic effects. In the late 1990s and throughout the 2000s, multi-FX manufacturers such as Zoom and Korg produced devices that were increasingly feature-laden. Multi-FX devices combine several effects together, and most devices allow users to use preset combinations of effects, including distortion, chorus, reverb, compression, and so on. This allows musicians to have quick on-stage access to different effects combinations. Some multi-FX pedals contain modelled versions of well-known effects pedals or amplifiers.
The Boss GT-8, a higher-end multi-effect processing pedal; note the preset switches and patch bank foot switches and built-in expression pedal.
Multi-effects devices have garnered a large share of the effects device market, because they offer the user such a large variety of effects in a single package. A low-priced multi-effects pedal may provide 20 or more effects for the price of a regular single-effect pedal. More expensive multi-effect pedals may include 40 or more effects, amplifier modelling, and the ability to combine effects and/or modelled amp sounds in different combinations, as if the user was using multiple guitar amps. More expensive multi-effects pedals may also include more input and output jacks (e.g., an auxiliary input or a "dry" output), MIDI inputs and outputs, and an expression pedal, which can control volume or modify effect parameters (e.g., the rate of the simulated rotary speaker effect).
By the 1980s and 1990s, software effects became capable of replicating the analog effects used in the past. These new digital effects attempt to model the sound produced by analog effects and tube amps, with varying degrees of quality. There are many free guitar effects computer programs that can be downloaded from the Internet. Now, computers with sound cards can be used as digital guitar effects processors. Although digital and software effects offer many advantages, many guitarists still use analog effects.
In 2002, Gibson announced the first digital guitar, which performs analog-to-digital conversion internally. The resulting digital signal is delivered over a standard Ethernet cable, eliminating cable-induced line noise. The guitar also provides independent signal processing for each individual string. In 2003, modelling amplifier maker Line 6 introduced the Variax guitar. It differs in some fundamental ways from conventional solid-body electrics. It has on-board electronics capable of modelling the sound of a variety of unique guitars and some other stringed instruments. At one time, some models featured piezoelectric pickups instead of the conventional electromagnetic pickups.
A prepared guitar
The sound of a guitar can not only be adapted by electronic sound effects but is also heavily affected by various new techniques developed or becoming possible in combination with electric amplification. This is called extended technique.
Extended techniques include:
The hammer-on technique Palm muting of the strings using the picking hand Slide guitar
Other techniques, such as axial finger vibrato, pull-offs, hammer-ons, palm muting, harmonics and altered tunings, are also used on the classical and acoustic guitar. Shred guitar is a genre involving a number of extended techniques.
Paul Reed Smith Standard 22 Gittler electric guitar, a bodyless guitar without fingerboard or neck Fender Esquire
Unlike acoustic guitars, solid-body electric guitars have no vibrating soundboard to amplify string vibration. Instead, solid-body instruments depend on electric pickups and an amplifier (or amp) and speaker. The solid body ensures that the amplified sound reproduces the string vibration alone, thus avoiding the wolf tones and unwanted feedback associated with amplified acoustic guitars of the period. These guitars are generally made of hardwood covered with a hard polymer finish, often polyester or lacquer. In large production facilities, the wood is stored for three to six months in a wood-drying kiln before being cut to shape. Premium custom-built guitars are frequently made with much older, hand-selected wood.
One of the first solid-body guitars was invented by Les Paul. Gibson did not present their Gibson Les Paul guitar prototypes to the public, as they did not believe the solid-body style would catch on. Another early solid-body Spanish style guitar, resembling what would become Gibson's Les Paul guitar a decade later, was developed in 1941 by O.W. Appleton, of Nogales, Arizona. Appleton made contact with both Gibson and Fender but was unable to sell the idea behind his "App" guitar to either company. In 1946, Merle Travis commissioned steel guitar builder Paul Bigsby to build him a solid-body Spanish-style electric. Bigsby delivered the guitar in 1948. The first mass-produced solid-body guitar was Fender Esquire and Fender Broadcaster (later to become the Fender Telecaster), first made in 1948, five years after Les Paul made his prototype. The Gibson Les Paul appeared soon after to compete with the Broadcaster. Another notable solid-body design is the Fender Stratocaster, which was introduced in 1954 and became extremely popular among musicians in the 1960s and 1970s for its wide tonal capabilities and more comfortable ergonomics than other models.
Some solid-bodied guitars, such as the Gibson Les Paul Supreme, the PRS Singlecut, and the Fender Telecaster Thinline, among others, are built with hollows in the body. These hollows are designed specifically not to interfere with the critical bridge and string anchor point on the solid body. In the case of Gibson and PRS, these are called chambered bodies. The motivation for this may be to reduce weight, to achieve a semi-acoustic tone (see below) or both.
Main article: Semi-acoustic guitar Epiphone semi-acoustic hollow-body guitar
Semi-acoustic guitars have a hollow body (similar in depth to a solid-body guitar) and electronic pickups mounted on the body. They work in a similar way to solid-body electric guitars except that, because the hollow body also vibrates, the pickups convert a combination of string and body vibration into an electrical signal. Whereas chambered guitars are made, like solid-body guitars, from a single block of wood, semi-acoustic and full-hollowbody guitars bodies are made from thin sheets of wood. They do not provide enough acoustic volume for live performance, but they can be used unplugged for quiet practice. Semi-acoustics are noted for being able to provide a sweet, plaintive, or funky tone. They are used in many genres, including blues, funk, sixties pop, and indie rock. They generally have cello-style F-shaped sound holes. These can be blocked off to prevent feedback, as in B. B. King's famous Lucille. Feedback can also be reduced by making them with a solid block in the middle of the soundbox.
Main article: Archtop guitar
Full hollow-body guitars have large, deep bodies made of glued-together sheets, or "plates", of wood. They can often be played at the same volume as an acoustic guitar and therefore can be used unplugged at intimate gigs. They qualify as electric guitars inasmuch as they have fitted pickups. Historically, archtop guitars with retrofitted pickups were among the very earliest electric guitars. The instrument originated during the Jazz Age, in the 1920s and 1930s, and are still considered the classic jazz guitar (nicknamed "jazzbox"). Like semi-acoustic guitars, they often have f-shaped sound holes.
Having humbucker pickups (sometimes just a neck pickup) and usually strung heavlly, jazzboxes are noted for their warm, rich tone. A variation with single-coil pickups, and sometimes with a Bigsby tremolo, has long been popular in country and rockabilly; it has a distinctly more twangy, biting tone than the classic jazzbox. The term archtop refers to a method of construction subtly different from the typical acoustic (or "folk" or "western" or "steel-string" guitar): the top is formed from a moderately thick (1 inch or 2–3 cm) piece of wood, which is then carved into a thin (0.1 in, or 2–3 mm) domed shape, whereas conventional acoustic guitars have a thin, flat top.
Main article: Acoustic-electric guitar
Some steel-string acoustic guitars are fitted with pickups purely as an alternative to using a separate microphone. They may also be fitted with a piezoelectric pickup under the bridge, attached to the bridge mounting plate, or with a low-mass microphone (usually a condenser mic) inside the body of the guitar that converts the vibrations in the body into electronic signals. Combinations of these types of pickups may be used, with an integral mixer/preamp/graphic equalizer. Such instruments are called electric acoustic guitars. They are regarded as acoustic guitars rather than electric guitars, because the pickups do not produce a signal directly from the vibration of the strings, but rather from the vibration of the guitar top or body.
Electric acoustic guitars should not be confused with semi-acoustic guitars, which have pickups of the type found on solid-body electric guitars, or solid-body hybrid guitars with piezoelectric pickups.
The one-string guitar is also known as the Unitar. Although rare, the one-string guitar is sometimes heard, particularly in Delta blues, where improvised folk instruments were popular in the 1930s and 1940s. Eddie "One String" Jones had some regional success. Mississippi blues musician Lonnie Pitchford played a similar, homemade instrument. In a more contemporary style, Little Willie Joe, the inventor of the Unitar, had a rhythm and blues instrumental hit in the 1950s with "Twitchy", recorded with the Rene Hall Orchestra.
The four-string guitar is better known as the tenor guitar. One of its best-known players was Tiny Grimes, who played on 52nd Street with the beboppers and played a major role in the Prestige Blues Swingers. Multi-instrumentalist Warren Ellis (musician) of Dirty Three and Nick Cave and the Bad Seeds is a contemporary player who includes a tenor guitar in his repertoire.
The four-string guitar is normally tuned CGDA, but some players, such as Tiny Grimes, tune to DGBE in order to preserve familiar 6-string guitar chord fingerings. The tenor guitar can also be tuned like a soprano, concert, or tenor ukulele, using versions of GCEA tuning.
Main article: Seven-string guitar Stephen Carpenter playing a 7-string electric guitar in 2009
Most seven-string guitars add a low B string below the low E. Both electric and classical guitars exist designed for this tuning. A high A string above the high E instead of the low B string is sometimes used. Another less common seven-string arrangement is a second G string situated beside the standard G string and tuned an octave higher, in the same manner as a twelve-stringed guitar (see below). Jazz guitarists using a seven-string include George Van Eps, Lenny Breau, Bucky Pizzarelli and his son John Pizzarelli.
Seven-string electric guitars were popularized among rock players in the 1980s by Steve Vai. Along with the Japanese guitar company Ibanez, Vai created the Universe series seven-string guitars in the 1980s, with a double locking tremolo system for a seven-string guitar. These models were based on Vai's six-string signature series, the Ibanez Jem. Seven-string guitars experienced a resurgence in popularity in the 2000s, championed by Deftones, Limp Bizkit, Slayer, KoRn, Fear Factory, Strapping Young Lad, Nevermore, Muse and other hard rock and metal bands. Metal musicians often prefer the seven-string guitar for its extended lower range. The seven-string guitar has also played an essential role in progressive metal rock and is commonly used in bands such as Dream Theater and Pain of Salvation and by experimental guitarists such as Ben Levin.
Main article: Eight-string guitar
Eight-string electric guitars are rare but not unused. One is played by Charlie Hunter, which was manufactured by Novax Guitars. The largest manufacturer of eight- to 14-string instruments is Warr Guitars. Their models are used by Trey Gunn (ex King Crimson), who has his own signature line from the company. Similarly, Mårten Hagström and Fredrik Thordendal of Meshuggah used 8-string guitars made by Nevborn Guitars and now guitars by Ibanez. Munky of the nu metal band KoRn is also known to use seven-string Ibanez guitars, and it is rumored that he is planning to release a K8 eight-string guitar similar to his K7 seven-string guitar. Another Ibanez player is Tosin Abasi, lead guitarist of the progressive metal band Animals as Leaders, who uses an Ibanez RG2228 to mix bright chords with very heavy low riffs on the seventh and eighth strings. Stephen Carpenter of Deftones also switched from a seven-string to an eight-string in 2008 and released his signature STEF B-8 with ESP Guitars. In 2008, Ibanez released the Ibanez RG2228-GK, which is the first mass-produced eight-string guitar. Jethro Tull's first album uses a nine-string guitar. Bill Kelliher, guitarist for the heavy metal group Mastodon, worked with First Act on a custom mass-produced nine-string guitar.
Main article: Ten-string guitar
B.C. Rich manufactures a ten-string six-course electric guitar, the Bich, whose radical shape positions the machine heads for the four secondary strings on the body, avoiding the head-heaviness of many electric twelve-string guitars. However many players bought it for the body shape or electrics and simply removed the extra strings. The company recognized this and released six-string models of the Bich, but ten-string models also remain in production.
Main article: Twelve-string guitar
Twelve-string electric guitars feature six pairs of strings, usually with each pair tuned to the same note. The extra E, A, D, and G strings add a note one octave above, and the extra B and E strings are in unison. The pairs of strings are played together as one, so the technique and tuning are the same as a conventional guitar, but they create a much fuller tone, with the additional strings adding a natural chorus effect. They are used almost solely to play harmony and rhythm parts, rather than for guitar solos. They are relatively common in folk rock music. Lead Belly is the folk artist most identified with the twelve-string guitar, usually acoustic with a pickup.
George Harrison of the Beatles and Roger McGuinn of the Byrds brought the electric twelve-string to notability in rock and roll. During the Beatles' first trip to the United States, in February 1964, Harrison received a new 360/12 model guitar from the Rickenbacker company, a twelve-string electric made to look onstage like a six-string. He began using the 360 in the studio on Lennon's "You Can't Do That" and other songs. McGuinn began using electric twelve-string guitars to create the jangly, ringing sound of the Byrds. Both Jimmy Page, the guitarist with Led Zeppelin, and Leo Kottke, a solo artist, are well known as twelve-string guitar players.
Main article: 3rd bridge
The third-bridge guitar is an electric prepared guitar with an additional, third bridge. This can be a normal guitar with, for instance, a screwdriver placed under the strings, or it can be a custom-made instrument. Lee Ranaldo of Sonic Youth plays with a third bridge.
Main article: Double neck guitar A Gibson EDS-1275
Double-neck (or, less commonly, "twin-neck") guitars enable guitarists to play both guitar and bass guitar or, more commonly, both a six-string and a twelve-string. In the mid-1960s, one of the first players to use this type of guitar was Paul Revere & the Raiders' guitarist Drake Levin. Another early user was John McLaughlin. The double-neck guitar was popularized by Jimmy Page, who used a custom-made, cherry-finished Gibson EDS-1275 to perform "Stairway to Heaven", "The Song Remains the Same" and "The Rain Song", although for the recording of "Stairway to Heaven" he used a Fender Telecaster and a Fender XII electric twelve-string. Mike Rutherford of Genesis and Mike + the Mechanics is also famous for his use of a double-neck guitar during live shows. Don Felder of the Eagles used the Gibson EDS-1275 during the Hotel California tour. Muse guitarist and vocalist Matthew Bellamy uses a silver Manson double-neck on his band's Resistance Tour. Rush guitarist Alex Lifeson is also known for using double-neck guitars in the live performance of several songs. In performances of the song "Xanadu" during the band's 2015 R40 anniversary tour, Lifeson played a white Gibson EDS-1275 double-neck guitar with six-string and twelve-string necks, while bassist Geddy Lee performed with a double-neck Rickenbacker guitar with four-string bass and twelve-string guitar necks.
Popular music and rock groups often use the electric guitar in two roles: as a rhythm guitar which provides the chord sequence or "progression" and sets out the "beat" (as part of a rhythm section), and a lead guitar, which is used to perform melody lines, melodic instrumental fill passages, and guitar solos. In some rock or metal bands with two guitarists, the two performers may perform as a guitar tandem, and trade off the lead guitar and rhythm guitar roles. In bands with a single guitarist, the guitarist may switch between these two roles, playing chords to accompany the singer's lyrics, and then playing a guitar solo in the middle of the song.
Gibson Les Paul has been used in many genres, including rock, country, pop, soul, rhythm and blues, blues, jazz, reggae, punk, and heavy metal
In the most commercially available and consumed pop and rock genres, electric guitars tend to dominate their acoustic cousins in both the recording studio and live venues, especially in the "harder" genres such as heavy metal and hard rock. However the acoustic guitar remains a popular choice in country, western and especially bluegrass music, and it is widely used in folk music. Even metal and hard rock guitarists play acoustic guitars for some ballads and for MTV unplugged acoustic performances.
Jazz guitar playing styles include rhythm guitar-style "comping" (accompanying) with jazz chord voicings (and in some cases, walking basslines) and "blowing" (improvising solos) over jazz chord progressions with jazz-style phrasing and ornaments. The accompanying style for electric guitar in most jazz styles differs from the way chordal instruments accompany in many popular styles of music. In rock and pop, the rhythm guitarist usually performs the chords in dense and regular fashion, which sets out the beat of a tune. Rock and pop chord voicings tend to focus on the first, third, and fifth notes of the chord. In contrast, in many modern jazz styles, the guitarist plays much more sparsely, intermingling periodic chords and delicate voicings into pauses in the melody or solo. Jazz chord voicings are usually rootless and emphasize the third and seventh notes of the chord. Jazz chords also often include the 9th, 11th and 13th notes of the chord, which are called "extensions".
When jazz guitar players improvise, they use scales, modes, and arpeggios associated with the chords in a tune's chord progression. Jazz guitarists have to learn how to use scales (whole tone scale, chromatic scale, etc.) to solo over chord progressions. Jazz guitar improvising is not merely the recitation of jazz scales and rapid arpeggios. Jazz guitarists try to imbue their melodic phrasing with the sense of natural breathing and legato phrasing used by horn players such as saxophone players. As well, a jazz guitarists' solo improvisations have to have a rhythmic drive and "time feel" that creates a sense of "swing" and "groove". In addition to the traditional rhythm/comping and lead/blowing roles, some jazz guitarists use the electric instrument to play unaccompanied, combining harmony notes and the melody to form a complete piece of music, like classical guitarists.
Most jazz guitarists play hollow-body instruments, but solid-body guitars are also used. Hollow-body instruments were the first guitars used in jazz in the 1930s and 1940s. During the 1970s jazz fusion era, many jazz guitarists switched to the solid body guitars that dominated the rock world, using powerful guitar amps to get a loud sound.
Electric guitars with acoustic guitars in the background
Until the 1950s, the acoustic, nylon-stringed classical guitar was the only type of guitar favored by classical, or art music composers. In the 1950s a few contemporary classical composers began to use the electric guitar in their compositions. Examples of such works include Luciano Berio's Nones (1954) Karlheinz Stockhausen's Gruppen (1955–57); Donald Erb's String Trio (1966), Morton Feldman's The Possibility of a New Work for Electric Guitar (1966); George Crumb's Songs, Drones, and Refrains of Death (1968); Hans Werner Henze's Versuch über Schweine (1968); Francis Thorne's Sonar Plexus (1968) and Liebesrock (1968–69), Michael Tippett's The Knot Garden (1965–70); Leonard Bernstein's MASS (1971) and Slava! (1977); Louis Andriessen's De Staat (1972–76); Helmut Lachenmann's Fassade, für grosses Orchester (1973, rev. 1987), Valery Gavrilin Anyuta (1982), Steve Reich's Electric Counterpoint (1987), Arvo Pärt's Miserere (1989/92), György Kurtág's Grabstein für Stephan (1989), and countless works composed for the quintet of Ástor Piazzolla. Alfred Schnittke also used electric guitar in several works, like the "Requiem", "Concerto Grosso N°2" and "Symphony N°1".
In the 1970s, 1980s and 1990s, a growing number of composers (many of them composer-performers who had grown up playing the instrument in rock bands) began writing contemporary classical music for the electric guitar. These include Frank Zappa, Shawn Lane, Steven Mackey, Nick Didkovsky, Scott Johnson, Lois V Vierk, Tim Brady, Tristan Murail, and Randall Woolf.
Yngwie Malmsteen released his Concerto Suite for Electric Guitar and Orchestra in 1998, and Steve Vai released a double-live CD entitled Sound Theories, of his work with the Netherlands Metropole Orchestra in June 2007. The American composers Rhys Chatham and Glenn Branca have written "symphonic" works for large ensembles of electric guitars, in some cases numbering up to 100 players, and the instrument is a core member of the Bang on a Can All-Stars (played by Mark Stewart). Still, like many electric and electronic instruments, the electric guitar remains primarily associated with rock and jazz music, rather than with classical compositions and performances.R. Prasanna plays a style of Indian classical music (Carnatic music) on the electric guitar.
In the 21st century, European avant garde composers like Richard Barrett, Fausto Romitelli, Peter Ablinger, Bernhard Lang, Claude Ledoux and Karlheinz Essl have used the electric guitar (together with extended playing techniques) in solo pieces or ensemble works. Probably the most ambitious and perhaps significant work to date is Ingwe (2003–2009) by Georges Lentz (written for Australian guitarist Zane Banks), a 60-minute work for solo electric guitar, exploring that composer's existential struggles and taking the instrument into realms previously unknown in a concert music setting.
In Vietnam, electric guitars are often used as an instrument in cải lương music (traditional southern Vietnamese folk opera), sometimes as a substitute for certain traditional stringed instruments like the Đàn nguyệt (two-stringed lute) when they are not available. Electric guitars used in cải lương are played in finger vibrato (string bending), with no amplifiers or sound effects.
An electric guitar store
Mesa-Boogie "Mark IV", a guitar combo amplifier
A guitar amplifier (or guitar amp) is an electronic amplifier that strengthens the weak electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which are typically housed in a wooden cabinet. A guitar amplifier may be a standalone wood or metal cabinet that contains only the power amplifier (and preamplifier) circuits, requiring the use of a separate speaker cabinet–or it may be a "combo" amplifier, which contains both the amplifier and one or more speakers in a wooden cabinet. There is a wide range of sizes and power ratings for guitar amplifiers, from small, lightweight "practice amplifiers" with a single 8" speaker to heavy combo amps with four 10" speakers and a powerful amplifier, which are loud enough to use in a nightclub or bar performance.
Guitar amplifiers can also modify the instrument's tone by emphasizing or de-emphasizing certain frequencies, using equalizer controls, which function the same way as the bass and treble knobs on a home hi-fi stereo, and by adding electronic effects; distortion (also called "overdrive") and reverb are commonly available as built-in features. The input of modern guitar amplifiers is a 1/4" jack, which is fed a signal from an electro-magnetic pickup (from an electric guitar) or a piezoelectric pickup (usually from an acoustic guitar) using a patch cord, or a wireless transmitter. For electric guitar players, their choice of guitar amp and the settings they use on the amplifier are a key part of their signature tone or sound. Some guitar players are longtime users of a specific amp brand or model. Many electric guitar players use external effects pedals to alter the sound of their tone before the signal reaches the guitar amp, such as the wah wah pedal and the chorus pedal.
This article focuses on electric guitar amps. For information on amps for bass guitar, a lower-pitched, similar instrument, see the article on bass amps.
A Fender Bassman amp head with a 15" speaker cabinet.
Typically, guitar amplifiers have two amplifying circuit stages and in addition frequently have tone-shaping electric circuits, which usually include at least bass and treble controls, which function similarly to the equivalent controls on a home hi-fi system. More expensive amplifiers typically have more controls for other frequency ranges, such as one or two "midrange" controls and a "presence" control for very high frequencies. Some guitar amplifiers have a graphic equalizer, which uses vertical fader controls which can control many frequency bands. The first amplifier stage is a preamplifier stage (there may be more than one), which amplifies the guitar signal to a level that can drive the power stage. The power amplifier or output stage produces a high current signal to drive a loudspeaker to produce sound that the guitarist and audience can hear.
There may be one or more tone stages that affect the character of the guitar signal:
Tone stages may also provide electronic effects—such as equalization, compression, distortion, chorus, or reverb. Amplifiers may use vacuum tubes (called valves in Britain), solid-state (transistor) devices, or both.
There are two configurations of guitar amplifiers: combination ("combo") amplifiers, which include an amplifier and one or more speakers in a wooden cabinet, and the standalone amplifier (often called a "head" or "amp head"), which does not include a speaker, but passes the amplified signal via a speaker cable to one or more external speaker cabinets. A wide range of speaker configurations are available in guitar cabinets, ranging from cabinets with a single speaker (e.g., 1×10" or 1×12") or multiple speakers (e.g., 2×10", 4×10" or 8x10"). Guitar amplifiers have a wide range in price and quality. Music equipment companies import small, low-powered practice amplifiers for students and beginners that sell for less than $50 USD. Other companies produce expensive custom-made amplifiers for professional musicians, which can cost thousands of dollars. Most combo amplifiers have a carrying handle, and many combo amplifiers and cabinets have metal or plastic-reinforced corners to protect the amp during transportation.
Control knobs are typically mounted on the front of the cabinet or chassis, though in some cases, the knobs are on a recessed panel at the back of the top of the amplifier. The most basic amps only have a few knobs, which typically control volume, bass and treble. More expensive amps may have a number of knobs that control pre-amp volume (or "gain"), distortion or overdrive, volume, bass, mid and treble, and reverb. Some older amps (and their re-issued versions) have a knob that controls a vibrato effect. The 1/4" input jack is typically mounted on the front of the amplifier. In the simplest, least expensive amplifiers, this 1/4" jack is the only jack on the amplifier. More expensive amplifiers may have a patch bay for multiple inputs and outputs, such as a pre-amp out (for sending to another guitar amplifier), an in jack to create an effects loop (when used with the pre-amp out jack), an external speaker output (for powering an additional speaker cabinet), and stereo RCA jacks or an 1/8" jack, for connecting a CD player or MP3 player so that a player can practice along with recorded music. Some amps have a 1/4" jack for connecting a pedal to turn the amp's onboard overdrive and reverb on and off or to switch between channels. The vast majority of guitar amps can only be powered by AC mains power (plugging into a wall outlet); however, a small number of practice amps designed for buskers also have battery power, enabling them to be used for street performances.
A 1940s-era Valvo combo amp. Fender Deluxe 1953
In the 1920s, it was very hard for a musician playing a pickup-equipped guitar to find an amplifier and speaker to make their instrument louder as the only speakers that could be bought were "radio horns of limited frequency range and low acoustic output". The cone speaker, widely used in 2000s-era amp cabinets, was not offered for sale until 1925. The first amplifiers and speakers could only be powered with large batteries, which made them heavy and hard to carry around. When engineers developed the first AC mains-powered amplifiers, they were soon used to make musical instruments louder. Engineers invented the first loud, powerful amplifier and speaker systems for public address systems and movie theaters. These large PA systems and movie theatre sound systems were very large and very expensive, and so they could not be used by most touring musicians. After 1927, smaller, portable AC mains-powered PA systems that could be plugged into a regular wall socket "quickly became popular with musicians"; indeed, "...Leon McAuliffe (with Bob Wills) still used a carbon mic and a portable PA as late as 1935." During the late 1920s to mid-1930s, small portable PA systems and guitar combo amplifiers were fairly similar. These early amps had a "single volume control and one or two input jacks, field coil speakers" and thin wooden cabinets; remarkably, these early amps did not have tone controls or even an on-off switch.
In 1928, the Stromberg-Voisinet firm was the first company to sell an electric stringed instrument and amplifier package. However, musicians found that the amps had an "unsatisfactory tone and volume, [and] dependability problems", so the product did not sell well. Even though the Stromberg-Voisinet amp did not sell well, it still launched a new idea: a portable electric instrument amp with a speaker, all in an easily transported wooden cabinet. In 1929, Vega electrics launched a portable banjo amplifier. In 1932, Electro String Instruments and amplifier (this is not the same company asStromberg Electro Instruments) introduced a guitar amp with "high output" and a "string driven magnetic pickup". Electro set out the standard template for combo amps: a wooden cabinet with the electronic amplifier mounted inside, and a convenient carrying handle to facilitate transporting the cabinet. 1n 1933, Vivi-Tone amp set-ups were used for live performances and radio shows. In 1934, Rickenbacker launched a similar combo amp which added the feature of metal corner protectors, which keep the corners in good condition during transportation.
In 1933, Dobro released an electric guitar and amp package. The combo amp had "two 8″ Lansing speakers and a five-tube chassis. Dobro made a two speaker combo amp that was on the market over 12 years before Fender launched its two-speaker "Dual Professional/Super" combo amp. In 1933, Audio-Vox was founded by Paul Tutmarc, the inventor of the first electric bass (Tutmarc's instrument did not achieve market success until Leo Fender's launched the Precision Bass). In 1933, Vega sold a "pickup and amplifier set" which a musician could use with her/his existing guitar. In that same year, the Los Angeles-based Volu-Tone company also sold a pickup/amplifier set. Volu-Tone used "high voltage current" to sense the string vibration, a potentially dangerous approach that did not become popular. In 1934 Dobro released a guitar amp with a vacuum tube rectifier and two power tubes. By 1935, Dobro and National began selling combo amps for Hawaiian guitar. In 1934, Gibson developed prototype combo amps, but these never got produced and sold. By 1935, Electro/Rickenbacher sold "more amps and electric guitars than all the amps and electrified/electric guitars made from ’28 through the end of ’34, combined."
The first electric instrument amplifiers were not designed for use with electric guitars. The earliest examples were portable PA systems, which appeared in the early 1930s when the introduction of electrolytic capacitors and rectifier tubes allowed the production of economical built-in power supplies that could be plugged into wall sockets, instead of heavy multiple battery packs, since rechargeable batteries would not become lightweight until many decades later. While guitar amplifiers from the beginning were used to amplify acoustic guitar, electronic amplification of guitar was first widely popularized by the 1930s and 1940s craze for Hawaiian music, which extensively employed the amplified lap steel Hawaiian guitar.
In the 1920s, the earliest combo amplifiers did not have any tone controls. Tone controls on early guitar amplifiers were very simple and provided a great deal of treble boost, but the limited controls, the loudspeakers used, and the low power of the amplifiers (typically 15 watts or less prior to the mid-1950s) gave poor high treble and bass output. Some models also provided effects such as an electronic tremolo unit. Early Fender amps labeled tremolo as "vibrato" and labeled the vibrato arm of the Stratocaster guitar as a "tremolo bar" (see vibrato unit, electric guitar, and tremolo). Some later models included an onboard spring reverb effect, one of the first being the Ampeg Reverberocket amp.
Gibson Lancer GA-35 (mid-1960s) guitar amplifier
In the 1950s, several guitarists experimented with distortion produced by deliberately overdriving their amplifiers, including Goree Carter,Joe Hill Louis,Elmore James,Ike Turner,Willie Johnson,Pat Hare,Guitar Slim,Chuck Berry,Johnny Burnette, and Link Wray. In the early 1960s, surf rock guitarist Dick Dale worked closely with Fender to produce custom made amplifiers, including the first 100-watt guitar amplifier. He pushed the limits of electric amplification technology, helping to develop new equipment that was capable of producing "thick, clearly defined tones" at "previously undreamed-of volumes."
U2 guitarist The Edge's 1964 Vox AC30 combo amp.
Distortion became more popular from the mid-1960s, when The Kinks guitarist Dave Davies produced distortion effects by connecting the already distorted output of one amplifier into the input of another. Later, most guitar amps were provided with preamplifier distortion controls, and "fuzz boxes" and other effects units were engineered to safely and reliably produce these sounds. In the 2000s, overdrive and distortion has become an integral part of many styles of electric guitar playing, ranging from blues rock to heavy metal and hardcore punk.
Guitar combo amplifiers were at first used with bass guitars and electric pianos, but these instruments produce a wider frequency range and need a full-range speaker system. Much more amplifier power is required to reproduce low-frequency sound, especially at high volume. Reproducing low frequencies also requires a suitable woofer or subwoofer speaker and enclosure. Woofer enclosures must be larger and more sturdily built than cabinets for mid-range or high-frequency (tweeter) speakers. As such, in the 1950s, when Ampeg introduced bass amplifier and speaker systems, these began to be used by bass guitarists. Similarly, Hammond organ players used a specialized keyboard combo amplifier, the Leslie speaker cabinet, which contains a woofer for the low frequencies and a horn for the high frequencies. The Leslie horns rotated and a baffle around the woofer rotated as well, producing a chorus effect.
Kustom 200 bass amp – amp head and speakers, 100 watts RMS, two channels, two 15" speakers, 1971
Guitar amplifiers are manufactured in two main forms: a "combo" contains the amplifier and one or more speaker(s) in a single wooden speaker enclosure. A separate configuration is available as well, with a separate amplifier (the "head") on top of one or more cabinets, each of which contains one or more speakers. Another alternative device used for guitar are public address amplifiers. Grunge guitarist Kurt Cobain used four 800 watt PA amplifiers for his early guitar set-up.
Besides one or more instrument inputs (typically a 1/4" jack), other jacks may also be provided, such as an auxiliary input jack (sometimes with its own level control, for a drum machine), "send" and "return" jacks to create an effects loop, an extension speaker jack. Practice amps may have stereo RCA or mini jacks for connecting a CD player, portable media player or other sound source and a 1/4" headphone jack. Some guitar amps have an XLR input so that a microphone can be plugged in for singing. Guitar amps that include a mic input are in effect small, portable PA systems.
A wide range of instrument amplifiers is available at a wide range of price, quality, and performance levels. Some amplifiers are designed for beginners, such as small, low-wattage "practice amplifiers", which typically have a single 8" speaker and about 10 watts, or smaller "combo" amps with relatively low wattage (15 to 20 watts) and a single 10" speaker. Mid- to large-size "combo" amps with 30 to 50 watts and one 12" speaker or four 10" speakers are designed for use in band rehearsals and onstage performances. Some guitar amps are designed for specific instruments or particular genres, such as the Marshall amps, which are widely used in heavy metal music.
The glow from four "Electro Harmonix KT88" brand power tubes lights up the inside of a Traynor YBA-200 bass guitar amplifier
Vacuum tubes (called "valves" in British English) were by far the dominant active electronic components in most instrument amplifier applications until the 1970s, when solid-state semiconductors (transistors) started taking over. Transistor amplifiers are less expensive to build and maintain, reduce the weight and heat of an amplifier, and tend to be more reliable and more shock-resistant. Tubes are fragile and they need to be replaced and maintained periodically. As well, serious problems with the tubes can render an amplifier inoperable until the issue is resolved. In the 2000s, high-end tube instrument amplifiers (along with a small number of hi-fi power amplifiers used by audiophiles and high-end studio microphone preamplifiers) survive as the few exceptions, because of their perceived sound quality. Tube enthusiasts believe that tube amps produce a "warmer" sound and a more natural "overdrive" sound. Typically, tube amps use one or more dual triodes in the preamplifier section to provide sufficient voltage gain to offset tone control losses and drive the power amplifier section. While tube technology is, in many ways, outdated, tube amps remain popular since many guitarists prefer their sound.
Rear view of a tube (valve) combo guitar amplifier. Visible are two glass output tubes, six smaller preamp tubes in their metal tube retainers, and both the power transformer and the output transformer.
Since the 1980s, most inexpensive and mid-priced guitar amplifiers are based on semiconductor (solid-state) circuits. Some designs incorporate tubes in the preamp stage for their subjectively warmer overdrive sound—see "Hybrid amplifiers", below. Solid-state amplifiers are much cheaper to produce and more reliable, and they are usually much lighter than tube amplifiers. High-end solid-state amplifiers are less common, since many professional guitarists tend to favor vacuum tubes. Some jazz guitarists, however, tend to favor the "cleaner" sound of solid-state amplifiers; only a few solid-state amps have enduring attraction, such as the Roland Jazz Chorus. Solid-state amplifiers vary in output power, functionality, size, price, and sound quality in a wide range, from practice amplifiers to combos suitable for gigging to professional models intended for session musicians who do studio recording work.
A hybrid amplifier involves one of two combinations of tube and solid-state amplification. It may have a tube power amp fed by a solid-state pre-amp circuit, as in most of the original MusicMan Amps, later amplifier models from Alamo Electronics, the Fender Super Champ XD, and the Roland Bolt amplifier. Randall Amplifiers V2 and T2 use hybrid amp technology. Alternatively, a tube pre-amp can feed a solid-state output stage, as in models from Kustom, Hartke, SWR and Vox. This approach dispenses with the need for an output transformer and easily achieves modern power levels.
A modeling amplifier, shown from above. Note the various amplifier and speaker emulations selectable via the rotary knob on the left.
Microprocessor technology allows the use of digital onboard effects in guitar amps to create numerous different sounds and tones that simulate the sound of a range of tube amplifiers and different sized speaker cabinets, all using the same amplifier and speaker. These are known as modeling amplifiers, and can be programmed with simulated characteristic tones of different existing amplifier models (and speaker cabinets—even microphone type or placement), or dialed in to the user's taste. Many amps of this type are also programmable by way of USB connection to a home computer or laptop.Line 6 is generally credited with bringing modeling amplification to the market. Modeling amplifiers and stompbox pedals, rackmount units and software programs which provide amplifier, speaker cabinet and mic modeling can give a guitarist with the single modeling amp or unit access to a large number of sounds and tones, such as the simulated sound of tube amplifiers, vintage combo amplifiers, huge 8x10" stacks, without having to bring all of this heavy equipment to the studio or stage.
The use of "Full Range Flat Response" (FRFR) amplification systems by electric guitarists has received an extra impetus from modeling amplifiers. Before the widespread availability of modeling amplifiers and units, an electric guitarist would not be able to plug her/his electric guitar straight into a PA system or powered speaker, because in most rock genres, the tonal coloration that a regular guitar amp's preamplifier, equalization filters, power amp, guitar speaker and cabinet design (e.g., 8x10" cabinet) are an essential part of a guitarist's unique tone. The basic concept of FRFR is that the tone is shaped by sound processors placed in the signal chain before the amplifier/speaker stage. However, instead of a guitar amplifier, with its particular sound-shaping characteristics (e.g., many amps roll off high treble frequencies and many amplifiers add frequency coloration), a flat-frequency response amplification systems can be used, such as amplified speakers or a PA system (full-range speakers), or dedicated combo-style amplifiers with a broad frequency range. Such processors can be traditional guitar effects, a modeling amplifier (without power amplifier), or a computer running tone-shaping software. With an amp modeling pedal or unit, a guitarist could even use a flat-response keyboard amplifier combo amp to produce overdriven, vintage tones and sounds.
These amplifiers are intended for acoustic guitars, especially for the way these instruments are used in relatively quiet genres such as folk and bluegrass. They are similar in many ways to keyboard amplifiers, in that they have a relatively flat frequency response, and are usually designed so that neither power amplifier nor speakers add coloration. To produce this relatively "clean" sound, these amplifiers often have very powerful amplifiers (providing up to 800 watts RMS), to provide additional "Headroom" and prevent unwanted distortion. Since an 800 watt amplifier built with standard Class AB technology would be very heavy, some acoustic amplifier manufacturers use lightweight Class D amplifiers, which are also called "switching amplifiers."
Acoustic amplifiers are designed to produce a "clean", transparent, "acoustic" sound when used with acoustic instruments with built-in transducer pickups and/or microphones. The amplifiers often come with a simple mixer, so that the signals from a pickup and condenser microphone can be blended. Since the early 2000s, it has become increasingly common for acoustic amplifiers to provide a range of digital effects, such as reverb and compression. As well, these amplifiers often contain feedback-suppressing devices, such as notch filters or parametric equalizers.
Metal guitarist Klaus Eichstadt in front of his Marshall stack. A 3×6 stack of mock Marshall guitar cabinets for Jeff Hanneman of Slayer
An amplifier stack consists of an amplifier head atop a speaker cabinet—a head on top of one cabinet is commonly called a half stack, a head atop two cabinets a full stack. The cabinet that the head sits on often has an angled top in front, while the lower cabinet of a full stack has a straight front. The first version of the Marshall stack was an amp head on an 8×12 cabinet, meaning a single speaker cabinet containing eight 12" guitar speakers. After six of these cabinets were made, the cabinet arrangement was changed to an amp head on two 4×12 cabinets, meaning four 12" speakers, to enable the cabinets to be more transportable. Some touring metal and rock bands have used a large array of guitar speaker cabinets for their impressive appearance. Some of these arrangements include only the fronts of speaker cabinets mounted on a large frame.
There are many varieties of speaker combinations used in guitar speaker cabinets, including one 12" speaker, one 15" speaker (this is more common for bass amplifiers than for electric guitar cabinets), two 10" speakers, four 10" speakers, four 12" speakers, or eight 10" speakers. Less commonly, guitar cabinets may contain different sizes of speaker in the same cabinet. Cabinets with eight 10" speakers are large and heavy, and they are often equipped with wheels and a "towel bar"-style handle for transport. Some cabinets use mixed speaker types, such as one 15" speaker and two 10" speakers.
Combo guitar amplifier cabinets and guitar speaker cabinets use several different designs, including the "open back" cabinet, the closed back cabinet (a sealed box), and, less commonly, bass reflex designs which use a closed back along with a vent or port cut into the cabinet. With guitar amps, most "open back" amp cabinets are not fully open; in fact, part of the back is enclosed with panels. Combo guitar amp cabinets and standalone speaker cabinets are often made of plywood; "[d]ecent...cabs have even been constructed from MDF and particle board—although these are typically considered low-budget options." In a cabinet, "...the size and depth of the cabinet, the type of wood used to build it, the way that wood is fixed together, the type and thickness of the baffle material (the sheet of wood to which the speaker is mounted), and the way this baffle is mounted to the cab" all affect the sound and tone of the cabinet.
When two or more speakers are used in the same cabinet, or when two cabinets are used together, the speakers can be wired in parallel or in series, or in a combination of the two (e.g., two 2x10" cabinets, with the two speakers wired in series, can be connected together in parallel). Whether speakers are wired in parallel or in series affects the impedance of the system. Two 8 ohm speakers wired in parallel will have a 4 ohm impedance. Guitarists who are connecting multiple cabinets to their amplifier need to consider the minimum impedance of their amplifier. Whether speakers are wired in parallel or in series also affects the tone and sound. When speakers are wired in parallel, this "...dampen[s] and restrain[s]" the speakers, giving a "tighter response, and a smoother breakup"; speakers that are wired in "...series (usually no more than two) run a little looser, giving a slightly more raw, open and edgy sound."
A Marshall JCM 900's knobs for equalization, gain, reverb and volume.
For electric guitar amplifiers, there is often a distinction between "practice" or "recording studio" guitar amps, which tend to have output power ratings of less than one watt to 20 watts and "performance" or "stage" amps, which are generally 30 watts or higher. Traditionally, these have been fixed-power amplifiers, with some models having a half-power switch to slightly reduce the listening volume while preserving power-tube distortion.
The relationship between perceived volume and power output in watts is not immediately obvious. While beginners sometimes assume that there is a linear relationship between perceived volume and wattage (e.g., they assume that a 5-watt amp will be much quieter at its maximum output than a 50-watt amp), in fact the human ear perceives a 5-watt amplifier as half as loud as a 50-watt amplifier (a tenfold increase in power), and a half-watt amplifier is a quarter as loud as a 50-watt amp. Doubling the power of an amplifier results in a "just noticeable" increase in volume, so a 100-watt amplifier is only just noticeably louder than a 50-watt amplifier. Such generalizations are also subject to the human ear's tendency to behave as a natural compressor at high volumes.
Power attenuation can be used with either low-power or high-power amplifiers, resulting in variable-power amplifiers. A high-power amplifier with power attenuation can produce power-tube distortion through a range of listening volumes, but with a decrease in high power distortion. Other technologies, such as dual rectifiers and the Sag Circuit—which should not be confused with attenuation—allow high power amplifiers to produce low power volume while preserving high power distortion.
Speaker efficiency is also a major factor affecting a tube amplifier's maximum volume. For bass instruments, higher-power amplifiers are needed to reproduce low-frequency sounds. While an electric guitarist would be able to play at a small club with a 50-watt amplifier, a bass player performing in the same venue would probably need an amplifier with 200 or more watts.
Marshall is a popular amplifier manufacturer for metal and hard rock. Pictured is the MG15DFX guitar amplifier.
Distortion is a feature available on many guitar amplifiers that is not typically found on keyboard or bass guitar amplifiers. Tube guitar amplifiers can produce distortion through pre-distortion equalization, preamp tube distortion, post-distortion EQ, power-tube distortion, tube rectifier compression, output transformer distortion, guitar speaker distortion, and guitar speaker and cabinet frequency response. Because there are so many factors beyond preamp distortion that create a guitarist's "signature sound", in recording and sound reinforcement applications, the sound of the guitar amp is almost always recorded with a microphone placed in front of the guitar speaker, rather than using the guitar amp's pre-amp out signal (even though the guitar sound is typically recorded with a mic in front of the amp's speaker, for recordings, the sound engineer or music producer may ask for the DI out signal from the pickups to be recorded onto a separate track at the same time, so that the engineer or producer can re-amp the signal through various different amps at a later time). In contrast, it is fairly common to use a DI box with electric bass.
Distortion sound or "texture" from guitar amplifiers is further shaped or processed through the frequency response and distortion factors in the microphones (their response, placement, and multi-microphone comb filtering effects), microphone preamps, mixer channel equalization, and compression. Additionally, the basic sound produced by the guitar amplifier can be changed and shaped by adding distortion and/or equalization effect pedals before the amp's input jack, in the effects loop just before the tube power amp, or after the power tubes.
Power-tube distortion is required for amp sounds in some genres. In a standard master-volume guitar amp, as the amp's final or master volume is increased beyond the full power of the amplifier, power tube distortion is produced. The "power soak" approach places the attenuation between the power tubes and the guitar speaker. In the re-amped or "dummy load" approach, the tube power amp drives a mostly resistive dummy load while an additional low power amp drives the guitar speaker. In the isolation box approach, the guitar amplifier is used with a guitar speaker in a separate cabinet. A soundproofed isolation cabinet, isolation box, isolation booth, or isolation room can be used.
Even in the 2010s, the vintage Fender Bandmaster remains a sought-after amp by guitarists. Note the four inputs, two for regular sound and two which are run through the onboard vibrato effect unit. The amp pictured is a 1968 model.
A variety of labels are used for level attenuation potentiometers (knobs) in a guitar amplifier and other guitar equipment. Electric guitars and basses have a volume control on the instrument that attenuates the signal from selected pickups. There may be two volume controls on an electric guitar or bass, wired in parallel to mix the signal levels from the neck and bridge pickups. Rolling back the guitar's volume control also changes the pickup's equalization or frequency response, which can provide pre-distortion equalization.
The simplest guitar amplifiers, such as some vintage amps and modern practice amps, have only a single volume control. Most have two volume controls: a first volume control called "preamplifier" or "gain" and a master volume control. The preamp or gain control is designed differently on different types of guitar amps. On an amp designed for an acoustic guitar, turning up the preamp knob will preamplify the signal, but even at its maximum setting, the preamp control is unlikely to produce much overdrive. However, with amps designed for electric guitarists playing electric blues, hard rock and heavy metal music, turning up the preamp or gain knob will usually produce overdrive or distortion. Some electric guitar amps have three controls in the volume section: preamplifier, distortion and master control. Turning up the preamp and distortion knobs in varying combinations can create a range of overdrive tones, from a gentle, warm growling overdrive suitable for a traditional blues show or a rockabilly band to the extreme distortion used in hardcore punk and death metal. On some electric guitar amps, the "gain" knob is equivalent to the distortion control on a distortion pedal, and similarly may have a side-effect of changing the proportion of bass and treble sent to the next stage.
The patch bay at the rear panel of this Line 6 Flextone guitar amp provides a number of additional inputs and outputs, including stereo XLR DI unit outputs.
A simple, inexpensive amplifier may have only two tone controls, a passive bass and treble control. In some better quality amps, one or more midrange controls are provided. On the most expensive amps, there may be shelving equalizers for bass and treble, a number of mid-range controls (e.g., low mid, mid and high mid), and a graphic equalizer or parametric equalizer. The amplifier's master volume control restricts the amount of signal permitted through to the driver stage and the power amplifier. When using a power attenuator with a tube amplifier, the master volume no longer acts as the master volume control. Instead, the power attenuator's attenuation control controls the power delivered to the speaker, and the amplifier's master volume control determines the amount of power-tube distortion. Power-supply based power reduction is controlled by a knob on the tube power amp, variously labeled "wattage", "power", "scale", "power scale", or "power dampening".
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