Guitar amplifier
A guitar amplifier is an instrument amplifier designed for use with an electric guitar, bass guitar, or acoustic guitar. When a guitar amplifier's preamplifier and power amplifier circuits are combined with a speaker cabinet and one or more loudspeakers, it is known as a combo. When the circuits are housed in a dedicated enclosure, it is known as a head. There is a wide range of sizes and power ratings for guitar amplifiers, from small, low-wattage practice combos to heavy, 100-watt heads that are often paired with large external cabinets. In addition to amplifying the guitar's signal, amps typically modify its tone by emphasizing or de-emphasizing certain frequencies using equalizer controls and through producing distortion. Reverb is a common built-in effect.
Commercially available amplifiers were first released in 1928 but did not become widely used until the introduction of mass-produced solid-body electric guitars and basses in the 1950s. Notable brands include Fender, Marshall, Vox, and Mesa/Boogie. For players, their choice of amp and the settings they use are a key part of their tone or sound. Historically, guitar amplifiers have been designed around vacuum tubes, but solid-state technology and digital signal processing have also been used. Guitarists often use external effects pedals to alter their tone before the signal reaches the amplifier.
History
1920s–1940s: Early models
High-powered audio amplifiers were first developed for use as public address systems and in movie theaters. While initially bulky and expensive, technological developments in the 1920s allowed for smaller, portable models that became popular among musicians playing a variety of instruments, especially lap steel guitars. The first commercially available guitar amplifiers were released in 1928 by the companies Stromberg-Voisinet and Vega, although at the time there was little difference between these early amplifiers and portable PA systems. Models released through the mid-1930s typically used a thin, wooden cabinet, a metal chassis with no control panel, a single volume control, and one or two inputs. Power amp sections typically used output transformers built into their field coil speakers and generated under 10 watts of power, while their speakers were small, usually under 10 inches. Electro String Instruments released its first amplifier in 1932. Their design—using a small, rectangular wooden box with a cutout for a speaker and a handle on top—would serve as a template for other, pre-WWII models. An early pioneer of electric guitar, Alvino Rey used his Electro amp on hundreds of gigs and recordings at the time. In 1933, Dobro released its own amp model to compete with Electro's, whose amp would be updated with metal corners and a different grill cloth and released in 1934 under the Rickenbacker label. In 1935, Electro/Rickenbacher sold more amps and electric guitars than all the amps and electrified or electric guitars that had been made from 1928 through the end of 1934. Gibson also developed prototype amps around this time, but never released them.In the mid-1940s, K&F Manufacturing released their first amplifiers, low-wattage combos with steel casings and no covering. The K&F partnership was short-lived, however, with co-founder Leo Fender starting his own namesake brand, Fender, to continue producing amplifiers, as well as electric guitars and basses. Fender's first amps had wooden enclosures and were characterized by wide control panels that made them resemble television sets of the time. Like pickup models of that era, these early amplifiers were not loud enough for use on stage: when players turned their amps up all the way, the signal clipped, losing high and low frequencies but gaining compression, harmonics, and a "musical type of distortion". While an unintended technical shortcoming, players embraced it and amp distortion would go on to become closely associated with the electric guitar. One such amp known to distort at high volumes, the Fender Deluxe of 1948, became regarded as one of the earliest amp designs to achieve iconic status. Like other Fender amp models in the 1940s and 1950s, the Deluxe came in a Tweed-covered cabinet.
1950s–1960s: Rock and roll
In 1950, Fender debuted its first mass-produced, solid-body electric guitars, the Esquire and Telecaster. Using a solid-body design eliminated the unwanted feedback caused by pickups on acoustic jazz guitars when they were amplified. Fender released the Twin in 1950 and followed in 1952 with the bass-oriented Bassman. While the Twin excelled at clean tones, the Bassman's distortion at loud volumes became popular among both bassists and guitarists. The Bassman later served as inspiration for Marshall's debut amp model, the JTM45. Vox released its AC30 combo in 1958 and then updated the amp in 1960 as a three-channel model that became famous for its jangly tone and widespread use during the British Invasion. In response to players like Pete Townshend of The Who who wanted more power, Marshall released the 100-watt 1959 Super Lead in 1965. The JTM45 and Super Lead were heads, which combined the preamp and power amp in a dedicated enclosure that was paired with an external speaker cabinet. Pairing the Super Lead with one or more 4x12 cabinets became known as the "Marshall stack". The combination has been used by many notable guitarists of the era and played a major role in shaping the sound of rock and roll.Throughout the 1960s, Fender continued updating the circuits and cosmetics of their amplifiers. Fender's Twin Reverb of the mid-1960s became a standard amp model for "clean", undistorted tones. Hiwatt's DR103 was similarly highly regarded as a loud, clean amplifier and has frequently been associated with David Gilmour. In 1965, Peavey released its first amp models, which used transistors rather than the standard vacuum tubes, which had been replaced by solid-state technology in most industries following WWII. By the 1970s, Fender, Vox, Marshall, and others had all released transistor-based amplifiers, with the most successful being the Roland Jazz Chorus, which became a popular alternative to the Fender Twin for clean tones.
1970s–1980s: Master volume amplifiers
As rock music evolved, so too did the need among guitarists for greater amounts of distortion. Amps like Marshall's Super Lead could produce distortion but did so by a player pushing the power section into saturation by playing it at high volume levels that were not always practical. Many players turned to effects pedals like the Maestro Fuzz-Tone and Arbiter Fuzz Face as a solution, the former notably being used by Keith Richards on the Rolling Stones' hit " Satisfaction".By the early 1970s, it had become popular for technicians to "hot rod" Fender amplifiers to achieve more distortion through methods like adding a "master volume" circuit, which used two volume controls, one to control how much the preamp tubes distorted and another to control overall output. One such technician was Mesa/Boogie founder Randall Smith, whose modified Fenders evolved into the brand's Mark series, which used a series of variable gain stages that "cascaded" into each other to create more distortion than any previous amplifier could. In doing so, Smith pioneered "high-gain" amps. Howard Dumble used a similar cascading gain design with his Overdrive Special, which gave players a foot-switchable "lead" mode with extra gain stages.
While early Mesas and Dumbles were popular among guitarists like Carlos Santana, the heavier guitar tones of Black Sabbath's Tony Iommi using a Laney Supergroup amplifier and a modified Dallas Rangemaster treble booster inspired players in the growing heavy metal genre to pursue more aggressive tones. Marshall looked to meet this demand with the 1981 release of the JCM800 2203, which was initially a close copy of the brand's first master volume-equipped amp, the JMP 2203, released in 1975, but underwent several circuit changes in the next few years. Throughout the 1980s, Mesa/Boogie continued revising its Mark series, pioneering new features with their MKII iterations like channel-switching and effects loops. Smith and his company's most significant revision produced the Mark IIC+ variant, which had a tighter, more aggressive tone that was popularized by Metallica. The JCM800 and Mark series marked a transition from "vintage"-style amplifiers to modern designs.
Technicians in the 1980s continued pushing modded amplifiers into higher-gain territory, and some became successful enough to launch their own companies, including Soldano, Bogner, and Rivera. Soldano's SLO-100 helped establish the high-end, high-gain amplifier market and inspired later German brands like ENGL, Hughes & Kettner, and Diezel. Toward the end of the decade, many professional guitarists adopted complex rackmount setups, often consisting of multiple preamps, power amps, and studio-grade effects, all operated with a custom pedal controller. Popular rackmount preamps included the A/DA MP-1, Mesa/Boogie Triaxis, Marshall JMP-1, and Soldano X88-R.
1990s–present: Boutique brands and digital modeling
While rackmount setups were widely used by pros, they were expensive, and by the time affordable rackmount options came to the market in the early 1990s grunge had inspired a return to standalone amplifiers, vintage-style effects pedals, and a less processed sound. The 1990s also experienced a new wave of boutique amplifier builders. The old Fender and Marshall amps previous techs had modded were by then too valuable to alter, so many instead founded companies that built new amps inspired by vintage designs. A notable example was Matchless and their Vox AC30-inspired DC-30 combo. Other companies continued to push the boundaries of high-gain, with Mesa/Boogie's Dual Rectifier becoming the decade's quintessential high-gain amplifier. Peavey's 5150, co-designed with Eddie Van Halen, became another frequently-used amplifier among metal guitarists.Modeling technology advanced significantly during this time. Tech 21 had released its analog SansAmp amplifier modeler in 1989 but it became popular in the 1990s as a direct recording solution. Line 6 released its first digital modeling amplifier, the AxSys, in 1996, followed by the bean-shaped desktop POD processor two years later. Early modelers were regarded as home practice tools until the 2006 arrival of Fractal Audio's Axe-FX, the first modeler considered sufficient for professional use. The Kemper Profiler followed in 2011, pioneering "profiling", also known as "capturing", a technology that allows users to create and use digital versions of their own physical gear. The success of digital modeling in an otherwise analog landscape has led to a long-running debate over the merits of tube amplifiers compared to modelers. Tube amp players often appreciate the nostalgia of the technology and argue analog amps and cabinets have a "soul" that cannot be replicated; modeler users value their portability, consistency, and reliability.
Many tube amp manufacturers have responded by implementing digital technology into their products, especially impulse responses, which are digital emulations of speaker cabinets and microphones. IRs allow for easier home recording, letting players skip the use of physical cabinet setups while still using a tube amplifier. Alongside the development of modelers, smaller "lunchbox" amplifiers—amp heads that use metal cases and a low-output power stage—have become popular following the success of the 15-watt Orange Tiny Terror, released in 2006. Boss debuted its Katana line of analog-digital hybrid amplifiers in 2016, and it became the industry's bestselling amp line.
As digital signal processing technology has progressed, modelers have become more compact and inexpensive, with budget offerings from brands like Mooer, NUX, and Joyo. Many brands now incorporate AI and machine learning into their products and design process. One such company, Neural DSP, established itself through audio plug-ins that create computer-based virtual amplifier and effects modelling suites. Neural released their first piece of hardware, the Quad Cortex, in 2020.