An instrument amplifier is an electronic device that converts the often barely audible or purely electronic signal of a musical instrument into a larger electronic signal to feed to a loudspeaker. An instrument amplifier is used with musical instruments such as an electric guitar, an electric bass, electric organ, electric piano, synthesizers and drum machine to convert the signal from the pickup or other sound source into an electronic signal that has enough power, due to being routed through a power amplifier, capable of driving one or more loudspeaker that can be heard by the performers and audience.
A Fender "combo" amplifier. The combination amplifier is a preamplifier, power amplifier and tone controls and one or more loudspeakers or drivers mounted in a portable wooden cabinet. This amp's sound is being picked up with a microphone in a recording studio.
A Vox AC30 used by The Beatles
A small Gibson "combo" amplifier.
A 3×6 stack of mock Marshall guitar cabinets for Jeff Hanneman of Slayer
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal. It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a power gain greater than one.
A McIntosh stereo audio amplifier with output power of 50 watts per channel used in home component audio systems in the 1970s.
De Forest's prototype audio amplifier of 1914. The Audion (triode) vacuum tube had a voltage gain of about 5, providing a total gain of approximately 125 for this three-stage amplifier.
Power amplifier by Skyworks Solutions in a Smartphone.
An LM741 general purpose op-amp