A preamplifier, or simply preamp, is a device that connects and amplifies the audio signal from various audio/visual source components, such as CDs, DVDs, or Blu-ray Disc players. The preamplifier can be used to switch between sources, process audio or video, and deliver an audio output signal to what is called a power amplifier.

In a preamplifier-to-power amplifier configuration, the preamplifier handles the input sources and signal processing, while the power amplifier is the component that delivers the signal and power needed by the speakers to produce sound.

This means that you cannot connect speakers directly to a preamplifier unless the speakers are self-powered speakers with RCA input jacks. It is also important to note that AV preamplifiers/processors provide outputs that can be connected to a powered subwoofer.

In a home theater, preamplifiers are also called control amplifiers, AV processors, AV preamplifiers, or preamplifier/processors because of their role in decoding or processing audio and processing and upscaling video.