Shop online: Headphone Amplifier, Power Amplifier, Integrated Amplifiers, Preamplifier. What is an Amplifier? According to the Wikipedia site: An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power of a signal (a time-varying voltage or current). 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 a circuit that has a power gain greater than one. Source: https://en.wikipedia.org/wiki/Amplifier