Product Code Database
A guitar amplifier (or amp) 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 , 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 (or greater) 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 (also known as overdrive). 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 timbre 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.
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 Fender tweed.
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.
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 . 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.
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 (IRs), 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 Amps Tiny Terror, released in 2006. Boss Corporation debuted its Boss 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 that create computer-based virtual amplifier and effects modelling suites. Neural released their first piece of hardware, the Quad Cortex, in 2020.
The first amplifier stage is a preamplifier. It amplifies the audio signal to a level that can drive the power stage. The preamplifier also changes the tone of the signal; high preamp settings add overdrive. The Amplifier produces a high current signal to drive a loudspeaker and produce sound.
Various types of tone stages may affect the guitar signal:
Tone stages may also provide electronic effects—such as equalization, compression, distortion, chorus effect, or reverb. Amplifiers may use tube amplifier (called valves in Britain), solid-state (transistor) devices, or both.
The two common guitar amplifier configurations are a combination ("combo") amplifier that includes an amplifier and one or more speakers in a single cabinet, and a standalone amplifier (often called a head or amp head), which 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—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 vary widely in price and quality. Many music equipment companies import small, low-powered practice amplifiers for students and beginners that sell for less than $50. Other companies produce expensive custom-made amplifiers for professional musicians, which can cost hundreds or even thousands of dollars (USD). 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 and buttons are typically 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 several 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 or tremolo 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), a second low gain input, to use with active basses, 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 a 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. Some amps have an XLR jack for a microphone, either for the guitar amp to be used for singing (in effect as a mini-PA system), or, for acoustic guitar, to mix a mic signal with a pickup signal.
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 are designed for also have battery power so they can be used for street performances.
In the 1920s, guitarists played through public address amplifiers, but by the 1940s this was uncommon.
Besides instrument inputs and speaker outputs (typically via 1/4" jacks), an amp may have other inputs and outputs. These can include an auxiliary input jack (sometimes with its own level control, for a drum machine), send and return jacks to create an effects loop, a line out jack, and an extension speaker jack. Practice amps sometimes have a 1/4" headphone jack, or stereo RCA connector or mini jacks for connecting a CD player, portable media player or other sound sources. Some guitar amps have an XLR connector input so that a microphone can be plugged in for singing. Guitar amps that include a mic input are in effect small, portable . Some amps, typically bass amps, have an XLR connector to provide a balanced line from the preamp section to a PA system or recording input.
Instrument amplifiers are available in a wide range of price, quality, and performance levels. Some are designed for beginners, such as small, low-wattage practice amps, 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 best for high-volume situations, such as band rehearsals and onstage performances. For large venues, such as outdoor , guitarists may use one or more 100 watts (or several hundred watts) heads with one or more 8x10” cabinets.
While tube-based circuitry is technologically outdated, tube amps remain popular since many guitarists prefer their sound. Tube enthusiasts believe that tube amps produce a warmer sound and a more natural "overdrive" sound.
High-end solid-state amplifiers are less common, since many professional guitarists favor vacuum tubes. Some jazz guitarists 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 who do sound recording.
Alternatively, a tube preamplifier 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.
The use of full range, flat response (FRFR) amplification systems by electric guitarists has received an extra impetus from modeling amplifiers. Before widespread availability of modeling, guitarists did not commonly plug electric guitars straight into or because most genres relied on the tonal coloration of a regular guitar amplifier setup—from the preamplifier, equalization filters, power amp, , and cabinet design. The FRFR approach assumes the tone is shaped by sound processors in the signal chain before the amplifier and speaker stage, so it strives to not add further coloration 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. Using a modeling amp or a multi-effects pedal used with line level output, a guitarist can plug in the guitar into a flat response mic input or into a keyboard amplifier.
Acoustic amplifiers produce an uncolored, acoustic sound when used with acoustic instruments with built-in transducers, pickups or microphones. The amplifiers often come with a simple mixer, so that the signals from a pickup and a 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 Gain compression. As well, these amplifiers often contain feedback-suppressing devices, such as or parametric equalizers.
There are many varieties of speaker combinations used in guitar speaker cabinets, including one 12" speaker, one 15" speaker (this is more common for 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 speakers 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.
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 have 4-ohm impedance. Guitarists who connect multiple cabinets to an amplifier must consider the amp's minimum impedance. Parallel vs. series also affects tone and sound. Speakers wired in parallel slightly dampens and restrains them, giving what some describe as tighter response and smoother breakup. Some describe speakers wired in series (usually no more than two) as sounding "...looser, giving a slightly more raw, open and edgy sound."
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.Guitar Player Magazine, March 2004, page 179
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.
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 before the amp's input jack, in the effects loop just before the tube power amp, or after the power tubes.
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 works differently on different guitar amp designs. On an amp designed for acoustic guitar, turning up the preamp knob pre-amplifies 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 blues, hard rock and heavy metal music, turning up the preamp or gain knob usually produces overdrive distortion. Some electric guitar amps have three controls in the volume section: pre-amplifier, 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.
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, several 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.
|
|
