Instrument amplifier

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 (with guitars and other string instruments and some keyboards) or other sound source (e.g, a synthesizer's signal) 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. 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 (with guitars and other string instruments and some keyboards) or other sound source (e.g, a synthesizer's signal) 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 ('combo') 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 (or, less commonly, moulded plastic). 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 (adjusting bass and treble tone) or adding electronic effects such as intentional distortion/overdrive, reverb or chorus effect. Instrument amplifiers are available for specific instruments, including the electric guitar, electric bass, electric/electronic keyboards, and acoustic instruments such as the mandolin and banjo. Some amplifiers are designed for specific styles of music, such as the 'traditional'-style 'tweed' guitar amplifiers, such as the Fender Bassman used by blues and country music musicians, and the Marshall amplifiers used by hard rock and heavy metal bands. Unlike home 'hi-fi' amplifiers or public address systems, which are designed to accurately reproduce the source sound signals with as little harmonic distortion as possible and without changing the tone or equalization (at least not unless the hi-fi owner adjusts it themselves with a graphic equalizer), instrument amplifiers are often designed to add additional tonal coloration to the original signal, emphasize (or de-emphasize) certain frequencies (most electric guitar amps roll off the very high frequencies), and, in the case of guitar amplifiers designed for electric guitar or Hammond organ, offer the capability to intentionally add some degree of 'overdrive' or distortion to the tone. The two exceptions are keyboard amplifiers designed for use with digital pianos and synthesizers and 'acoustic' instrument amplifiers for use with acoustic guitar or fiddle in a folk music setting, which typically aim for a relatively flat frequency response (i.e., no added colouration of the sound) and little or no distortion of the signal. A guitar amplifier amplifies the electrical signal of an electric guitar (or, less commonly, with acoustic amplifiers, an acoustic 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 with controls that emphasize or de-emphasize certain frequencies and add electronic effects. String vibrations are sensed by a suitable microphone or pickup, depending on the type of guitar. For electric guitars, strings are almost always made of metal, and the pickup works by electro-magnetic induction (these are called magnetic pickups; they are the most widely used type of pickup on electric guitars). Acoustic guitars do not usually have a built-in pickup or microphone, at least with entry-level and beginner instruments. Some acoustic guitars have a small condenser microphone mounted inside the body, which designed to convert acoustic vibrations into an electrical signal, but usually they do so from direct contact with the strings (replacing the guitar's bridge) or with the guitar's body, rather than having a membrane like general-purpose microphones. Acoustic guitars may also use a piezoelectric pickup, which converts the vibrations of the instrument into an electronic signal. More rarely, a magnetic pickup may be mounted in the sound hole of an acoustic guitar; while magnetic pickups do not have the same acoustic tone that microphones and piezo pickups can produce, magnetic pickups are more resistant to acoustic feedback. Standard amplifiers, such as the Fender 'tweed'-style amps (e.g., the Fender Bassman) and Gibson amps, 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 ('harp') players. Combo amplifiers such as the Fender Super Reverb have powerful, loud tube amplifiers, four 10' speakers, and they often have built-in reverb and 'vibrato' effects units. Smaller guitar amps are also available, which have fewer speakers (some have only one speaker) and lighter, less powerful amplifier units. Smaller guitar amps are easier to transport to gigs and sound recording sessions. Smaller amps are widely used in small venue shows (nightclubs) and in recordings, because players can obtain the tone they want without having to have an excessively loud volume. One of the challenge with the large, powerful 4x10 Fender Bassman-type amps is that to get the tone a player wants, they have to turn up the amp to a loud volume. These amps are designed to produce a variety of sounds ranging from a clean, warm sound (when used in country and soft rock) to a growling, natural overdrive, when the volume is set near its maximum, (when used for blues, rockabilly, psychobilly, and roots rock). These amplifiers usually have a sharp treble roll-off at 5 kHz to reduce the extreme high frequencies, and a bass roll-off at 60–100 Hz to reduce unwanted boominess. The nickname 'tweed' refers to the lacquered beige-light brown fabric covering used on these amplifiers.