Instrument amplifier

Unlike home hi-fi amplifiers or public Address systems, which are designed to accurately reproduce the source sound signals with as little distortion as possible, instrument amplifiers are often designed to add additional tonal coloration to the original signal, and in many cases intentionally add some degree of distortion.

Most guitar amplifiers can also modify the instrument's sound with controls that emphasize or de-emphasize certain frequencies and add electronic effects.

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.

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).

Electric guitar amplifiers designed for heavy metal are used to add an aggressive drive, intensity, and edge to the guitar sound with distortion effects, preamplification boost controls (sometimes with multiple stages of preamps), and tone filters.

As a result, to get a loud electric guitar sound, early heavy metal and rock-blues bands often used stacks of 4x12" Marshall speaker cabinets on the stage.

In 1969, Jimi Hendrix used four stacks to create a powerful lead sound, and in the early 1970s by the band Blue Öyster Cult used an entire wall of Marshall Amplifiers to create a roaring wall of sound that projected massive volume and sonic power.

They differ from amplifiers for the electric guitar in several respects, with extended low-frequency response, and tone controls optimized for the needs of bass players.

Larger, more powerful bass amplifiers (300 or more watts) are often provided with internal or external metal heat sinks and/or fans to help keep the components cool.

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.

The vintage Leslie speaker cabinet and modern recreations, which are generally used for Hammond organs, use a tube amplifier that is often turned up to add a warm, growling overdrive.

Since the early 2000s, it is increasingly common for acoustic amplifiers to provided digital effects, such as reverb and compression.

Hi-fi home stereo amplifiers strive to accurately reproduce signals from pre-recorded music, with as little harmonic distortion as possible.

In contrast, instrument amplifiers are add additional tonal coloration to the original signal or emphasize certain frequencies.

As a result, in many large venues much of the onstage sound reaching the musicians now comes from in-ear monitors, not from the instrument amplifiers.

While stacks of huge speaker cabinets and amplifiers are still used in concerts (especially in heavy metal), this is often mainly for aesthetics or to create a more authentic tone.

The switch to smaller instrument amplifiers makes it easier for musicians to transport their equipment to performances.

Instrument amplifiers may be based on thermionic (tube or valve) or solid state (transistor) technology.

[2] By the 1960s and 1970s, semiconductor transistor-based amplifiers began to become more popular because they are less expensive, more resistant to bumps during transportation, lighter-weight, and require less maintenance.

The output transistors of solid-state amplifiers can be passively cooled by using metal fins called heatsinks to radiate away the heat.