page_title: Instrument amplifier
section_title: Hard rock and heavy metal
hierarchical_section_title: Instrument amplifier / Types / Guitar amplifiers / Hard rock and heavy metal
caption_attribution_description: English: bass amplifier stack An Acoustic 370 head with two David Eden bass loudspeaker cabinets, a 2x10 and a 1x15 This is an original photograph by Andrew Alder, taken on 16 September 2003.
context_page_description: An instrument amplifier is an electronic device that converts the often barely audible or purely electronic signal of a musical instrument into a larger electronic signal to feed to a loudspeaker. An instrument amplifier is used with musical instruments such as an electric guitar, an electric bass, electric organ, synthesizers and drum machine to convert the signal from the pickup or other sound source into an electronic signal that has enough power, due to being routed through a power amplifier, capable of driving one or more loudspeaker that can be heard by the performers and audience.
  Combination amplifiers include a preamplifier, a power amplifier, tone controls, and one or more speakers in a cabinet, a housing or box usually made of hardwood, plywood or particleboard. Instrument amplifiers for some instruments are also available without an internal speaker; these amplifiers, called heads, must plug into one or more external speaker cabinets. Instrument amplifiers also have features that let the performer modify the signal's tone, such as changing the equalization or adding electronic effects such as intentional distortion/overdrive, reverb or chorus effect.
context_section_description: Electric guitar amplifiers designed for 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 amplifiers (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, 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 systems at rock concerts were used mainly for the vocals. As a result, to get a loud electric guitar sound, early 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 clip or shear off the wave forms). 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" tone) with a foot-operated switch.
caption: A 2 x 10" bass speaker cabinet stacked on top of a 15" cabinet, with separate bass amplifier "head" unit
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