A receiver amplifier is a home theater component that performs the two basic functions of switching between different inputs, and amplifying audio signals before they are routed to loudspeakers. Receivers typically have a number of different inputs for both video and audio signals, and outputs for televisions and speakers. These devices often have both digital and analog inputs, and some can even convert between digital and analog. Unlike a processor, which requires a separate external amp to operate, a receiver amplifier can take an audio signal, increase the power, and route it directly to a series of loudspeakers. The number of speakers that a home theater surround sound system can support is dependent on how many channels the receiver is capable of outputting.
In home theater contexts, receivers are the components that are at the heart of most audio/video setups. Receivers typically have multiple audio and video inputs, so that digital video disc (DVD) players, compact disc (CD) players and all sorts of other devices can be plugged in at once. These components usually also have at least one video output that can connect to a television, and multiple speaker outputs. This makes it possible to have several audio and video devices hooked into the home theater system at once, and allows a user to easily switch between them.
The other main function of a receiver is to act as an amplifier, increasing the power of input signals so that they can be routed to loudspeakers. This means that receivers need to have some type of amplification circuitry, in addition to signal switching capability. In most cases a receiver amplifier will not have as much power as a dedicated amplifier, but is often sufficient for home theater applications. If more power is needed, some receivers are capable of acting as preamps. This type of receiver amplifier has specially marked outputs that are designed to be hooked into an external amplifier.
In addition to signal switching and amplification, there are also a few other functions that a receiver amplifier is sometimes capable of. Many of these devices have radio tuners, including both digital and satellite radio options. Digital signal processing (DSP) is another feature that is sometimes available. This capability can be limited to basic equalizer adjustments, though some receiver amplifier units are capable of simulating sound fields so that the listener is left with the impression of a venue such as an opera house or rock arena. Receiver amplifiers are typically also capable of decoding various types of multi-channel sound, which can be useful when watching movies and playing video games.
