A guitar amplifier (or guitar amp) is an electronic amplifier designed to make the signal of an electric or acoustic guitar louder and modify the tone by emphasizing or de-emphasizing certain frequencies and adding electronic effects.
The amplifier comprises a preamplifier stage, which amplifies the voltage of the signal from the guitar, and a power amplifier stage which delivers a higher current to the speaker to produce sound. The simplest guitar amplifiers have only a power switch and a volume knob, such as the Fender Champ. More complex amplifiers, like the Mesa Lonestar, have more than one volume control knob and tone control knobs to contour the low, mid and high audio frequencies. Such amps may also have additional control knobs for adjusting presence, drive, gain and solo channels. The preamplifier stage may also have electronic effects such as distortion, chorus, or reverb and additional controls such as a graphic equalizer. Amplifiers may use tubes (or valve)s, or solid state (transistor) devices, or a mixture of both. Guitar amplifiers are usually designed to produce high power with relatively high distortion; a guitar amplifier with certain components will generally be rated at a good deal more output power than a hi-fi amplifier with the same components.
There are two configurations of guitar amplifiers: combination ("combo") amplifiers, which include an amplifier and one, two, or four speakers in a wooden cabinet; and the standalone amplifier (often called a "head" or "amp head"), which does not include a speaker. Combo amplifiers range from small practice amplifiers with one 6" or 8" speaker and a 5 to 15 watt amplifier, to mid-sized combo amps with a 12" speaker and a 50 watt amplifier (suitable for rehearsals or performances in small venues), to large combo amplifiers with four 12" speakers and 100 or more watts of power, which can be used for shows in large clubs or halls. Amp heads are used with one or more speaker cabinets, creating what is nicknamed a "stack". Some guitarists who use amp heads and separate speaker cabinets use a single 4 X 12" speaker cabinet with the amp head. In some styles of music, such as heavy metal and blues rock, guitarists may connect the guitar amp head to a number of 4 X 12" cabinets. Most combo amps also have provisions for connecting to a larger speaker cabinet, such as a 4 x 12", for playing larger venues.
Bass guitars, which can play notes an octave or more below a regular guitar, are typically amplified with a bass amplifier which is designed to handle the low frequency range. Acoustic guitar amplifiers differ from electric guitar amplifiers in that while electric guitar amplifiers are typically designed to modify the tone of the instrument--either by "rolling off" high frequencies or adding the warmth of tube overdrive--acoustic guitar amplifiers are generally designed to reproduce the natural sound of the acoustic instrument fairly accurately, without adding coloration or overdrive. A bass guitar should never be played through a regular guitar amplifier, since the low frequency audio produced by the bass guitar can damage the guitar amplifier. Conversely, it is quite safe to play a guitar through a bass amplifier.
Guitar amplifiers range in price and quality from small, low-powered practice amplifiers, designed for students, which sell for less than US$50, to expensive "boutique" amplifiers which are custom-made for professional musicians and can cost thousands of dollars.
The amplifier comprises a preamplifier stage, which amplifies the voltage of the signal from the guitar, and a power amplifier stage which delivers a higher current to the speaker to produce sound. The simplest guitar amplifiers have only a power switch and a volume knob, such as the Fender Champ. More complex amplifiers, like the Mesa Lonestar, have more than one volume control knob and tone control knobs to contour the low, mid and high audio frequencies. Such amps may also have additional control knobs for adjusting presence, drive, gain and solo channels. The preamplifier stage may also have electronic effects such as distortion, chorus, or reverb and additional controls such as a graphic equalizer. Amplifiers may use tubes (or valve)s, or solid state (transistor) devices, or a mixture of both. Guitar amplifiers are usually designed to produce high power with relatively high distortion; a guitar amplifier with certain components will generally be rated at a good deal more output power than a hi-fi amplifier with the same components.
There are two configurations of guitar amplifiers: combination ("combo") amplifiers, which include an amplifier and one, two, or four speakers in a wooden cabinet; and the standalone amplifier (often called a "head" or "amp head"), which does not include a speaker. Combo amplifiers range from small practice amplifiers with one 6" or 8" speaker and a 5 to 15 watt amplifier, to mid-sized combo amps with a 12" speaker and a 50 watt amplifier (suitable for rehearsals or performances in small venues), to large combo amplifiers with four 12" speakers and 100 or more watts of power, which can be used for shows in large clubs or halls. Amp heads are used with one or more speaker cabinets, creating what is nicknamed a "stack". Some guitarists who use amp heads and separate speaker cabinets use a single 4 X 12" speaker cabinet with the amp head. In some styles of music, such as heavy metal and blues rock, guitarists may connect the guitar amp head to a number of 4 X 12" cabinets. Most combo amps also have provisions for connecting to a larger speaker cabinet, such as a 4 x 12", for playing larger venues.
Bass guitars, which can play notes an octave or more below a regular guitar, are typically amplified with a bass amplifier which is designed to handle the low frequency range. Acoustic guitar amplifiers differ from electric guitar amplifiers in that while electric guitar amplifiers are typically designed to modify the tone of the instrument--either by "rolling off" high frequencies or adding the warmth of tube overdrive--acoustic guitar amplifiers are generally designed to reproduce the natural sound of the acoustic instrument fairly accurately, without adding coloration or overdrive. A bass guitar should never be played through a regular guitar amplifier, since the low frequency audio produced by the bass guitar can damage the guitar amplifier. Conversely, it is quite safe to play a guitar through a bass amplifier.
Guitar amplifiers range in price and quality from small, low-powered practice amplifiers, designed for students, which sell for less than US$50, to expensive "boutique" amplifiers which are custom-made for professional musicians and can cost thousands of dollars.
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