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A keyboard amplifier, used for the stage piano, synthesizer, clonewheel organs and similar instruments, is distinct from other types of amplification systems due to the particular challenges associated with keyboards; namely, to provide solid low-frequency sound reproduction ''and'' crisp high-frequency sound reproduction with a relatively flat frequency response and low distortion. It is typically a combination amplifier that contains a two, three, or four-channel mixer, a pre-amplifier for each channel, equalization controls, a power amplifier, a speaker, and a horn, all in a single cabinet. A notable exception to the "low distortion" rule is keyboard amplifiers designed for the Hammond organ or clonewheel organs, such as the vintage Leslie speaker cabinet and modern recreations, which have a tube amplifier which is often turned up to add a warm, "growling" overdrive to the organ sound. ==Design== Since keyboards have a very wide range of pitches, keyboard amplifiers have to provide solid low-frequency sound reproduction ''and'' crisp high-frequency sound reproduction. This distinction affects the design of the loudspeakers, the speaker cabinet and the preamplifier and amplifier. They usually include tuned bass reflex ports or vents for increased efficiency at low frequencies. Since keyboard amplifiers have to be able to reproduce very high notes, they are often equipped with a horn. While electric guitar amplifiers are typically designed to modify the tone of the guitar (e.g., by adding distortion and rolling off high frequencies), keyboard amplifiers intended for general use for a range of keyboard applications usually have very low distortion and extended, flat frequency response in both directions. The exception to this rule is keyboard amplifiers designed for the Hammond organ, such as the vintage Leslie speaker cabinet and modern recreations, which have a tube amplifier which is often turned up to add a warm, "growling" overdrive to the organ sound. Unlike bass amplifiers and electric guitar amplifiers, keyboard amplifiers are rarely used in the "amplifier head" and separate speaker cabinets configuration. Instead, most keyboard amplifiers are "combo" amplifiers that integrate the amplifier, tone controls, and speaker into a single wooden cabinet. Another unusual aspect of keyboard amplifiers is that they are often designed with a "wedge" shape, as used with monitor speakers. This permits them to be used as monitor speakers (with the amplifier in front of the seated keyboardist, aiming up at them) which is more suitable for a seated keyboardist. Keyboard amplifiers often have an onboard three or four-channel mixer, so that multiple keyboards (e.g., a stage piano, synthesizer, and clonewheel organ) can be plugged into one amplifier and so that keyboardists can control the tone and level of several keyboards. In some genres, such as progressive rock, for example, keyboardists may perform with several synthesizers, electric pianos, and electro-mechanical keyboards. Keyboard amplifiers often have onboard reverb effects. Most inexpensive to mid-priced amplifiers currently produced are based on semiconductor (solid-state) circuits. Solid-state amplifiers vary in output power, functionality, size, price, and sound quality in a wide range, from practice amplifiers to professional models. The smallest, most inexpensive practice amplifiers may have only two channels with volume controls and one or two tone controls. Home practice amps have from 20 to 30 watts of power, often through an 8" or 10" speaker. Small keyboard amplifiers designed for small band rehearsals have 50 to 75 watts, a 12-inch speaker, and possibly a tweeter. Large keyboard amplifiers designed for shows in large clubs or halls have 200 to 300 watts of power, a 12-inch or 15-inch speaker (or two 12-inch speakers), and a horn-loaded tweeter. Some keyboard amps may be equipped with a compressor or limiter to protect the speaker from damage when the amplifier is being used at high volume levels. Some keyboard amps have an extension speaker jack, which enables the amp to be connected to a second speaker cabinet. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Keyboard amplifier」の詳細全文を読む スポンサード リンク
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