An audio/video receiver (AVR) is a consumer electronics component used in a home theater. Its purpose is to receive audio and video signals from a number of sources, and to process them and provide power amplifiers to drive loudspeakers and route the video to displays such as a television, monitor or video projector. Inputs may come from a satellite receiver, radio, DVD players, Blu-ray Disc players, VCRs or video game consoles, among others. The AVR source selection and settings such as volume, are typically set by a remote controller.
Usage
The term "receiver" basically refers to an amplifier, typically at least a two-channel stereo model, that has a built-in radio tuner. With A/V receivers, the basic functionality is to receive an audio signal, amplify the audio signal to drive multiple speakers, and allow pass-through of the corresponding video signal to a display device such as a projector or a television. The receiver performs tasks that would otherwise require numerous separate pieces of equipment, such as preamplifiers, equalizers, multiple power amplifiers, and so on.
As home entertainment options expanded in the 1980s and 1990s, so did the role of the receiver. The ability to handle a variety of digital audio signals was added. More amplifiers were added for surround-sound playback. Video switching was added to simplify changing from one device to another, though this role diminished again once TVs began supporting multiples of the same type of input connector.
The term audio/video receiver (AVR) or Home Theater Receiver is used to distinguish the multi-channel audio/video receiver (home theater receiver) from the simpler stereo receiver, though the primary function of both is amplification.
AV receivers may also be known as digital audio-video receivers or digital media renderers.
The AV receiver is classified as an audio frequency electronic amplifier. But with the addition of several features in the 2000s, AV receivers in the 2010s generally have significant additional functionality.
Features
Channels
Stereo receivers have two channels of amplification (thus two separate amplifiers), while AV receivers may have more than two. The standard for AV receivers is five channels of amplification (thus five separate amplifiers), usually referred to as 5.1 receivers. This provides for a left, right, center, left surround sound and right surround sound speaker to be powered by the receiver.
In the 2010s, 7.1 receivers became more common and provide for two additional surround channels, left rear surround and right rear surround. The ".1" refers to the LFE (low-frequency effects/bass) channel, the signal of which is usually sent to an amplified subwoofer unit. 5.1 and 7.1 receivers do not usually provide amplification for this channel. Instead, they provide a line level output. The user then either buys a separate monophonic power amp for their subwoofer or obtains a powered subwoofer cabinet, which contains an integrated power amplifier.
Amplifier power
Audio amplifier power, normally specified in watts, is not always as significant as it may seem from the specification. Due to the logarithmic nature of human hearing, audio power or sound pressure level (SPL), must be increased by ten times to sound twice as loud. This is why SPL is measured on a logarithmic scale in decibels (dBs). An increase of 10dBs results in a perceived doubling of loudness. Another complication with human hearing is that as the SPL decreases the perceived volume of the low and high frequencies decreases faster than the central frequencies around 2 kHz.
There are different standards for rating amplifier power depending on country, manufacturer, and model. Other factors also come into play: distortion, headroom, speaker efficiency. As well, some lower-price point manufacturers advertise the peak power of an amplifier, rather than its root mean square (RMS) power. Thus, it is possible for an amplifier with a specified lower power to sound louder than an amplifier with a specified higher power. Because of these factors, it is not easy to compare the perceived loudness of amplifiers solely from their specified power in watts.
Decoders
AV receivers usually provide one or more decoders for sources with more than two channels of audio information. This is most common with movie soundtracks, which use one of a variety of different types of encoding formats.