An amplifier is a piece of equipment which is used to dramatically boost (or "amplify") an electronic signal from an input device and in turn route in to a speaker (or speakers) so that it can be converted into sound. They can vary hugely in size and power, from the lowly 5-watt practice amp to the behemoth 100 watt stadium shaking 'Stack', and beyond. Amps usually have a series of controls for equalization (most often 3-band), input gain, output gain (or "Master Volume") and occasionally compression, reverb, vibrato and other effects.
Despite working with a variety of instruments and microphones, Amplifiers are most commonly associated with Electric Guitars
, and as such have been monumental in destroying eardrums, annoying neighbours, and generally shaping the face of popular music, from their initial pairing in the 1930s right up to today.