An audio amplifier is an electronic device that increases the power of audio signals. It takes a weak audio signal, such as from a microphone or musical instrument, and boosts it so that it can drive speakers or headphones, producing louder sound. Amplifiers are essential in various audio systems, including home theaters, concert sound systems, and personal audio devices. There are different types of audio amplifiers, including class A, class B, and class D, each with unique characteristics and efficiencies. They can be found in various forms, such as standalone units or built into receivers and speakers. The choice of amplifier affects sound quality and performance in audio playback.