page_title: Guitar amplifier
section_title: Volume controls
hierarchical_section_title: Guitar amplifier / Distortion, power, and volume / Volume controls
caption_attribution_description: IMG_0675
context_page_description: A guitar amplifier is an electronic device or system 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 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 6" speaker and a 10 watt amp to heavy combo amps with four 10” or four 12" speakers and a powerful 100 watt 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 and reverb are commonly available as built-in features.
context_section_description: 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 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, 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".
caption: 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.
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