Editing Instrument amplifier (section)

===Guitar amplifiers===
[[File:Guitarras de McCartney y Harrison.jpg|thumb|upright|A [[Vox AC30]] guitar amplifier used by [[The Beatles]]]]
{{Main|Guitar amplifier}}

A guitar amplifier amplifies the electrical signal of an [[electric guitar]] so that it can drive a [[loudspeaker]] at sufficient volume for the performer and audience to hear. Most guitar amplifiers can also modify the instrument's sound with controls that emphasize or de-emphasize certain frequencies and add [[effects unit|electronic effects]]. String vibrations are sensed by a [[Pick up (music technology)|pickup]]. For electric guitars, strings are made of metal, and the pickup works by [[electromagnetic induction]].

====Standard amps====
[[Image:Gibson 1.jpg|thumb|left|A small Gibson combo amplifier.]]

Standard amplifiers, such as the Fender ''tweed''-style amps (e.g., the [[Fender Bassman]]) are often used by traditional rock, blues, and country musicians who wish to create a vintage 1950s-style sound. They are used by electric guitarists, [[pedal steel]] guitar players, and [[blues harmonica]] players. These amps are designed to produce a variety of sounds ranging from a clean, warm sound to a growling, natural overdrive. These amplifiers usually have a sharp treble [[roll-off]] at 5&nbsp;kHz to reduce the extreme high frequencies, and a bass roll-off at 60–100&nbsp;Hz to reduce unwanted boominess. The nickname ''tweed'' refers to the lacquered beige-light brown fabric covering used on these amplifiers.

Combo amplifiers such as the [[Fender Super Reverb]] have powerful [[tube amplifier]]s, 10- or 12-inch speakers, and they often have built-in [[Reverberation|reverb]] and [[Vibrato unit|vibrato]] effects units. These larger combo amplifierss are used for club performances and larger venues. For large concert venues such as stadiums, performers may also use an amplifier ''head'' with several separate speaker cabinets. Smaller, lighter guitar amps are also available, which have less powerful amplifier units and as few as one speaker. Smaller guitar amps are easier to transport to gigs and [[sound recording]] sessions. Smaller amps are widely used in small venue shows, because players can obtain the tone they want without having to have an excessively loud volume.  The smallest combo amplifiers, which are mainly used for individual practice and warm-up purposes, may have only a single 8 or 10-inch speaker. Some players use these small combo amplifiers for concert performances, though, because it is easier to create natural overdrive with these lower-powered amplifiers.<!--[[User:Kvng/RTH]]-->

====Hard rock and heavy metal====
[[File:MarshallStack Slayer.jpg|thumb|A 3×6 stack of mock [[Marshall Amplification|Marshall]] guitar cabinets for [[Jeff Hanneman]] of [[Slayer]]]]
Electric guitar amplifiers designed for [[heavy metal music|heavy metal]] are used to add an aggressive ''drive'', intensity, and ''edge'' to the guitar sound with distortion effects, preamplification boost controls (sometimes with multiple stages of preamps), and tone filters. While many of the most expensive, high-end models use 1950s-style [[tube amplifier]]s (even in the 2000s), there are also many models that use [[transistor]] amplifiers, or a mixture of the two technologies (i.e., a tube preamplifier with a transistor [[power amplifier]]). Amplifiers of this type, such as [[Marshall amplifiers]], are used in a range of the louder, heavier genres of rock, including hard rock, [[Heavy metal music|heavy metal]], and [[hardcore punk]]. This type of amplifier is available in a range of formats, ranging from small, self-contained combo amplifiers for rehearsal and warm-ups to heavy ''heads'' that are used with separate speaker cabinets—colloquially referred to as a ''stack''.

In the late 1960s and early 1970s, [[Public Address system|public address systems]] at rock concerts were used mainly for the vocals. As a result, to get a loud electric guitar sound, early [[Heavy metal music|heavy metal]] and rock-blues bands often used stacks of 4x12" Marshall speaker cabinets on the stage. In 1969, [[Jimi Hendrix]] used four stacks to create a powerful lead sound, and in the early 1970s by the band [[Blue Öyster Cult]] used an entire wall of Marshall Amplifiers to create a roaring [[wall of sound]] that projected massive volume and sonic power. In the 1980s, metal bands such as [[Slayer]] and [[Yngwie Malmsteen]] also used ''walls'' of over 20 Marshall cabinets. However, by the 1980s and 1990s, most of the sound at live concerts was produced by the [[sound reinforcement system]] rather than the onstage guitar amplifiers, so most of these cabinets were not connected to an amplifier. Instead, walls of speaker cabinets were used for aesthetic reasons. 

Amplifiers for harder, heavier genres often use valve amplifiers (known as tube amplifiers in North America) also. Valve amplifiers are perceived by musicians and fans to have a warmer tone than those of transistor amps, particularly when overdriven (turned up to the level that the amplifier starts to [[clipping (electronics)|clip]] or shear off the waveforms). Instead of abruptly clipping off the signal at cut-off and saturation levels, the signal is rounded off more smoothly. Vacuum tubes also exhibit different harmonic effects than transistors. In contrast to the tweed-style amplifiers, which use speakers in an open-backed cabinet, companies such as Marshall tend to use 12" speakers in a closed-back cabinet. These amplifiers usually allow users to switch between clean and distorted tones (or a [[rhythm guitar]]-style ''crunch'' tone and a sustained [[lead guitar|"lead"]] tone) with a foot-operated switch.

[[Image:Bassstack.jpg|thumb|left|100px|A 2 x 10" bass speaker cabinet stacked on top of a 15" cabinet, with separate bass amplifier head unit]]