Keyboard amplifier

A keyboard amplifier is a powered electronic amplifier and loudspeaker in a speaker cabinet used for the amplification of electronic keyboard instruments. Keyboard amplifiers are distinct from other types of amplification systems such as guitar amplifiers due to the particular challenges associated with making keyboards sound louder on stage; namely, to provide solid low-frequency sound reproduction for the deep basslines that keyboards can play and crisp high-frequency sound for the high-register notes. Another difference between keyboard amplifiers and guitar/bass amplifiers is that keyboard amps are usually designed with a relatively flat frequency response and low distortion. In contrast, many guitar and bass amp designers purposely make their amplifiers modify the frequency response, typically to "roll-off" very high frequencies, and most rock and blues guitar amps, and since the 1980s and 1990s, even many bass amps are designed to add distortion or overdrive to the instrument tone (for bass, this is called "fuzz bass").

Keyboard amplifiers differ from guitar amplifiers and bass amplifiers in that whereas guitar and bass amps are usually designed for use with one guitar at a time, keyboard amplifiers almost always have a mixer with inputs for two, three, or four keyboards, because many performers often use multiple keyboards. For example, a single player may perform with a stage piano, a keytar and a synthesizer keyboard. Each channel input typically has its own pre-amplifier and volume knob. Keyboard amps in the lower cost range and power output range may only provide equalization controls (for modifying the bass and treble response) for the overall mix. Higher-priced, higher power output keyboard amps designed for professionals may have equalizer controls for each channel. Keyboard amplifiers also differ from guitar amps and bass amps in that whereas many guitar and bass amplifier companies often sell standalone amplifier units (which contain a preamplifier and power amplifier) for use with one or more separate speaker enclosures, keyboard amplifiers are almost always combination (or "combo") amplifiers, so-named because they combine a preamplifier, power amplifier, full-range speaker, and a horn-loaded tweeter, all in a single wooden speaker cabinet.

Two notable exceptions to the "low distortion" rule are keyboard amplifiers designed for the Hammond organ or clonewheel organs and amps used with electric pianos such as the Fender Rhodes. With organs used in blues or hard rock, performers often use 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. With electric pianos used in a rock or funk band, natural tube overdrive is often added to the sound.

Since keyboards have a very wide range of pitches, from deep bass notes to very high treble notes, 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 tweeter, which may be mounted in 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. Electric guitar amp combos and amps are usually designed to add coloration to the guitar tone or "sweeten" the tone. Keyboard amp combos are usually designed to reproduce the input signals. 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. Electric piano players in rock and funk also often seek to add natural tube overdrive to their sound.

Unlike bass amplifiers and electric guitar amplifiers, keyboard amplifiers are rarely used in the "amplifier head" and separate speaker cabinet 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.