Roles
Instrument amplifiers are designed for a different purpose than 'Hi-Fi' (high fidelity) stereo amplifiers used for radios and home stereo systems. Hi-fi home stereo amplifiers are designed to accurately reproduce the source sound signals from pre-recorded music, with as little harmonic distortion as possible. In contrast, instrument amplifiers are often designed to add additional tonal coloration to the original signal or emphasize certain frequencies. For electric instruments such as electric guitar, the amplifier helps to create the instrument's tone by boosting the input signal gain and distorting the signal, and by emphasizing frequencies deemed to be desirable (e.g., low frequencies) and de-emphasizing frequencies deemed to be undesirable (e.g., very high frequencies).
The two exceptions are keyboard amplifiers and acoustic amplifiers which are used by folk and bluegrass musicians for amplifying acoustic instruments such as acoustic guitar, violin, and mandolin. Acoustic amplifiers typically aim for a relatively flat response across the entire frequency range, much like a Public Address system.
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