AV receiver
Encyclopedia
AV receivers or audio-video receivers are one of the many consumer electronics
components typically found within a home theatre
system. Their primary purpose is to amplify sound from a multitude of possible audio sources as well as route video signals to your TV from various sources. The user may program and configure a unit to take inputs from devices such as DVD players, VCRs etc. and easily select which source he or she wants to route to their TV and have sound output for.
, a pre-amplifier and a power amplifier. These were generally called stereo receivers. The built-in tuner in these devices gave them the name receivers.
As home entertainment options expanded, 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 switching. Within the last few years, video processing has been added to many receivers.
The term audio/video receiver (AVR) or Home Theater Receiver is used to distinguish the simpler stereo receiver from the multi-channel audio video receiver.
and FM
radio reception. Satellite radio
tuners are also found in many modern receivers, allowing reception with just an external antenna (and a satellite radio subscription, if necessary).
Some models have HD Radio
tuners.
Some models have Internet Radio
and PC streaming access capabilities with an ethernet port.
The first common soundtrack format was Dolby Pro Logic
, a surround sound processing technology. This format contains a center channel
and a surround channel mixed into the left and right channels using a process called matrixing, providing a total of four channels. Receivers with Dolby Pro Logic decoders can separate out the center and surround channels from the left and right channels.
With the introduction of the DVD
, the Dolby Digital
format became a standard. Dolby Digital ready receivers included inputs and amplifiers for the additional channels. Most current AV receivers provide a Dolby Digital
decoder and at least one digital S/PDIF
input which can be connected to a source which provides a Dolby Digital
output.
A somewhat less common surround sound decoder called DTS is standard on current AV receivers.
When Dolby Labs and DTS introduced technologies to add a rear center surround channel, these technologies found their way into AV Receivers. Receivers with six amplifiers (known as 6.1 receivers) will typically have both Dolby and DTS's technologies. These are Dolby Digital EX and DTS ES.
Dolby introduced Dolby Pro Logic II to allow stereo sources to play back as if they were encoded in surround sound. DTS introduced a similar technology, NEO:6. These decoders have become common on most current receivers.
As the number of playback channels were increased on receivers, other decoders have been added to some receivers. For example, Dolby Labs created Dolby Pro Logic IIx to take advantage of receivers with more than five channels of playback.
With the introduction of high definition players (e.g. Blu-ray Disc
and HD DVD
), yet more decoders have been added to some receivers. Dolby TrueHD
and DTS-HD Master Audio
decoders are available on many receivers.
(DSP) made for handling various presets and audio effects. Some may offer simple equalizers and balance adjustments to complex DSP audio field simulations such as "Hall", "Arena", "Opera", etc. that simulate the audio being played in the places through use of surround sound and echo effects.
, left surround and right surround speaker to be powered by the receiver. 7.1 receivers are becoming 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) channel the signal of which is usually sent to an amplified subwoofer
unit. 5.1 and 7.1 receivers don't usually provide amplification for this channel. Instead, they provide a line level
output.
There are various standards for rating the output power of receivers. Different countries have different rules on how manufacturers specify the output ratings. Its not always possible to use these ratings to compare two products. Due to a number of factors such as real world behavior of speakers and dynamic headroom its possible for an amplifier with a lower rated power to play more loudly than one with a higher rated power.
Differences in output power are not always as significant as they may look. It takes 10 times the output power for the sound to be perceived as twice as loud. If 1 watt of output yields a sound pressure level of 90dB, it takes 10 watts to get an SPL of 100dB and 100 watts to get an SPL of 110dB. A 110 watt amplifier will not play 10% louder than a 100 watt amplifier.
Most receivers use class AB amplifiers. Some manufacturers are now producing receivers using class D amplifiers. Class D amplifiers are more efficient and can be made smaller and lighter than an equivalent class AB amplifier. There are also other designs such as class G and class H. Class G and H are variations on the conventional class AB design. Class G has two sets of power supply rails. Normally the power amp is fed from the lower voltage supply. This helps keep power dissipation in the output transistors down. When the signal exceeds the lower supply voltage, the amp switches to the higher voltage supply so the signal can be reproduced without clipping
. With a class H design, the supply rails are variable rather than two discrete steps. The signal actually modulates the supply voltage.
Analog audio connections usually use RCA plugs in stereo pairs. Inputs and outputs are both common. Outputs are provided mainly for cassette tape decks.
Analog audio connections using XLR connectors are uncommon, and usually found on more expensive receivers.
Digital connections allow for the transmission of PCM, Dolby Digital
or DTS audio. Common devices include CD players, DVD players, or satellite receivers.
Composite video connections use a single RCA plug on each end. Composite video is standard on all AV receivers allowing for the switching of video devices such as VHS players, cable boxes, and game consoles. DVD players may be connected via composite video connectors although a higher bandwidth connection is recommended.
S-Video connections offer better quality than composite video. It uses a DIN jack.
SCART connections generally offer the best quality video at standard-definition, due to the use of pure RGB signalling (although composite and S-Video may alternatively be offered over a SCART connector). SCART provides video and audio in one connection.
Component video has become the best connection for analog video as higher definitions such as 720p
have become common. The YPbPr
signalling provides a good compromise between resolution and colour definition.
HDMI is becoming common on AV receivers. It provides for the transmission of both audio and video. HDMI is relatively new technology and there are reported issues with devices not properly working with each other, especially cable/satellite boxes connected to a display through an AV receiver. Different levels of support are provided by receivers with HDMI connections. Some will only switch video and not provide for audio processing. Some will not handle multi-channel LPCM
. Multi-channel LPCM is a common way for Blu-ray and HD DVD
players to transmit the best possible audio.
or transcoding. A smaller number of receivers provide for de-interlacing
of video signals. For example, a receiver with upconversion, deinterlacing and upscaling can take an interlaced composite signal at 480i
(480 lines per frame sent as a field of 240 even numbered lines 0,2,4,8...478 followed by a field of 240 odd numbered lines 1,3,5,...479) and convert it to component video while also deinterlacing and upscaling it to a higher resolution such as 720p
(720 lines per frame with all lines in normal sequence 0,1,2...719).
Consumer electronics
Consumer electronics are electronic equipment intended for everyday use, most often in entertainment, communications and office productivity. Radio broadcasting in the early 20th century brought the first major consumer product, the broadcast receiver...
components typically found within a home theatre
Home cinema
Home cinema, also commonly called home theater, are home entertainment set-ups that seek to reproduce a movie theater experience and mood with the help of video and audio equipment in a private home....
system. Their primary purpose is to amplify sound from a multitude of possible audio sources as well as route video signals to your TV from various sources. The user may program and configure a unit to take inputs from devices such as DVD players, VCRs etc. and easily select which source he or she wants to route to their TV and have sound output for.
Usage
The term receiver originally referred to a component which included a tunerTuner
Tuner may refer to someone or something which adjusts or configures a mechanical, electronic, or musical device.- Electronic :* Antenna tuner, a device to adjust the resonance frequency of an antenna or transmission line...
, a pre-amplifier and a power amplifier. These were generally called stereo receivers. The built-in tuner in these devices gave them the name receivers.
As home entertainment options expanded, 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 switching. Within the last few years, video processing has been added to many receivers.
The term audio/video receiver (AVR) or Home Theater Receiver is used to distinguish the simpler stereo receiver from the multi-channel audio video receiver.
Radio reception
Receivers usually have a built in tuner for AMAmplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
and FM
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
radio reception. Satellite radio
Satellite radio
Satellite radio is an analogue or digital radio signal that is relayed through one or more satellites and thus can be received in a much wider geographical area than terrestrial FM radio stations...
tuners are also found in many modern receivers, allowing reception with just an external antenna (and a satellite radio subscription, if necessary).
Some models have HD Radio
HD Radio
HD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
tuners.
Some models have Internet Radio
Internet radio
Internet radio is an audio service transmitted via the Internet...
and PC streaming access capabilities with an ethernet port.
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.The first common soundtrack format was Dolby Pro Logic
Dolby Pro Logic
Dolby Pro Logic is a surround sound processing technology developed by Dolby Laboratories, designed to decode soundtracks encoded with Dolby Surround. Dolby Stereo was originally developed by Dolby in 1976 for analog cinema sound systems...
, a surround sound processing technology. This format contains a center channel
Center channel
Center channel refers to an audio channel common to many surround sound formats. It is the channel that is mostly, or fully, dedicated to the reproduction of the dialogue of an audiovisual program...
and a surround channel mixed into the left and right channels using a process called matrixing, providing a total of four channels. Receivers with Dolby Pro Logic decoders can separate out the center and surround channels from the left and right channels.
With the introduction of the DVD
DVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....
, the Dolby Digital
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...
format became a standard. Dolby Digital ready receivers included inputs and amplifiers for the additional channels. Most current AV receivers provide a Dolby Digital
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...
decoder and at least one digital S/PDIF
S/PDIF
S/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
input which can be connected to a source which provides a Dolby Digital
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...
output.
A somewhat less common surround sound decoder called DTS is standard on current AV receivers.
When Dolby Labs and DTS introduced technologies to add a rear center surround channel, these technologies found their way into AV Receivers. Receivers with six amplifiers (known as 6.1 receivers) will typically have both Dolby and DTS's technologies. These are Dolby Digital EX and DTS ES.
Dolby introduced Dolby Pro Logic II to allow stereo sources to play back as if they were encoded in surround sound. DTS introduced a similar technology, NEO:6. These decoders have become common on most current receivers.
As the number of playback channels were increased on receivers, other decoders have been added to some receivers. For example, Dolby Labs created Dolby Pro Logic IIx to take advantage of receivers with more than five channels of playback.
With the introduction of high definition players (e.g. Blu-ray Disc
Blu-ray Disc
Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...
and HD DVD
HD DVD
HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...
), yet more decoders have been added to some receivers. Dolby TrueHD
Dolby TrueHD
Dolby TrueHD is an advanced lossless multi-channel audio codec developed by Dolby Laboratories which is intended primarily for high-definition home-entertainment equipment such as Blu-ray Disc and HD DVD. It is the successor to the AC-3 Dolby Digital surround sound codec which was used as the...
and DTS-HD Master Audio
DTS-HD Master Audio
DTS-HD Master Audio is a lossless audio codec created by Digital Theater System. It was previously known as DTS++. It is an extension of DTS which, when played back on devices which do not support the Master Audio or High Resolution extension, degrades to a "core" track which is lossy. DTS-HD...
decoders are available on many receivers.
DSP effects
Most receivers offer specialized Digital Signal ProcessorsDigital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
(DSP) made for handling various presets and audio effects. Some may offer simple equalizers and balance adjustments to complex DSP audio field simulations such as "Hall", "Arena", "Opera", etc. that simulate the audio being played in the places through use of surround sound and echo effects.
Amplification
Stereo receivers have two channels of amplification, while AV receivers may have more than 2. The standard for AV receivers is five channels of amplification. These are usually referred to as 5.1 receivers. This provides for a left, right, centerCenter channel
Center channel refers to an audio channel common to many surround sound formats. It is the channel that is mostly, or fully, dedicated to the reproduction of the dialogue of an audiovisual program...
, left surround and right surround speaker to be powered by the receiver. 7.1 receivers are becoming more common and provide for two additional surround channels, left rear surround and right rear surround. The '.1' refers to the LFE
LFE
The low-frequency effects channel is the name of an audio track specifically intended for deep, low-pitched sounds ranging from 3-120 Hz. This track is normally sent to a speaker that is specially designed for low-pitched sounds called the subwoofer...
(low frequency effects) channel the signal of which is usually sent to an amplified subwoofer
Subwoofer
A subwoofer is a woofer, or a complete loudspeaker, which is dedicated to the reproduction of low-pitched audio frequencies known as the "bass". The typical frequency range for a subwoofer is about 20–200 Hz for consumer products, below 100 Hz for professional live sound, and below...
unit. 5.1 and 7.1 receivers don't usually provide amplification for this channel. Instead, they provide a line level
Line level
Line level is a term used to denote the strength of an audio signal used to transmit analog sound between audio components such as CD and DVD players, TVs, audio amplifiers, and mixing consoles, and sometimes MP3 players....
output.
There are various standards for rating the output power of receivers. Different countries have different rules on how manufacturers specify the output ratings. Its not always possible to use these ratings to compare two products. Due to a number of factors such as real world behavior of speakers and dynamic headroom its possible for an amplifier with a lower rated power to play more loudly than one with a higher rated power.
Differences in output power are not always as significant as they may look. It takes 10 times the output power for the sound to be perceived as twice as loud. If 1 watt of output yields a sound pressure level of 90dB, it takes 10 watts to get an SPL of 100dB and 100 watts to get an SPL of 110dB. A 110 watt amplifier will not play 10% louder than a 100 watt amplifier.
Most receivers use class AB amplifiers. Some manufacturers are now producing receivers using class D amplifiers. Class D amplifiers are more efficient and can be made smaller and lighter than an equivalent class AB amplifier. There are also other designs such as class G and class H. Class G and H are variations on the conventional class AB design. Class G has two sets of power supply rails. Normally the power amp is fed from the lower voltage supply. This helps keep power dissipation in the output transistors down. When the signal exceeds the lower supply voltage, the amp switches to the higher voltage supply so the signal can be reproduced without clipping
Clipping (audio)
Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum capability...
. With a class H design, the supply rails are variable rather than two discrete steps. The signal actually modulates the supply voltage.
AV inputs/outputs
There are a variety of possible connections on an AV receiver. Standard connectors include:- Analog audio (RCA connectorRCA connectorAn RCA connector, sometimes called a phono connector or cinch connector, is a type of electrical connector commonly used to carry audio and video signals...
, or occasionally XLR connectorXLR connectorThe XLR connector is a style of electrical connector, primarily found on professional audio, video, and stage lighting equipment. The connectors are circular in design and have between 3 and 7 pins...
) - Digital audio (S/PDIFS/PDIFS/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
; TOSLINKTOSLINKTOSLINK is a standardized optical fiber connection system. Also known generically as an "optical audio cable," its most common use is in consumer audio equipment , where it carries a digital audio stream from components such as MiniDisc, CD and DVD players, DAT recorders, computers, and modern...
or RCA terminated coaxial cableCoaxial cableCoaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
) - Composite videoComposite videoComposite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
(RCA connector) - S-VideoS-VideoSeparate Video, more commonly known as S-Video and Y/C, is often referred to by JVC as both an S-VHS connector and as Super Video. It is an analog video transmission scheme, in which video information is encoded on two channels: luma and chroma...
- SCARTSCARTSCART is a French-originated standard and associated 21-pin connector for connecting audio-visual equipment together...
video (primarily used in Europe and very uncommon in many other parts of the world) - Component videoComponent videoComponent video is a video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video information that is transmitted or stored as three separate signals...
- HDMIHigh-Definition Multimedia InterfaceHDMI is a compact audio/video interface for transmitting uncompressed digital data. It is a digital alternative to consumer analog standards, such as radio frequency coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA...
Analog audio connections usually use RCA plugs in stereo pairs. Inputs and outputs are both common. Outputs are provided mainly for cassette tape decks.
Analog audio connections using XLR connectors are uncommon, and usually found on more expensive receivers.
Digital connections allow for the transmission of PCM, Dolby Digital
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...
or DTS audio. Common devices include CD players, DVD players, or satellite receivers.
Composite video connections use a single RCA plug on each end. Composite video is standard on all AV receivers allowing for the switching of video devices such as VHS players, cable boxes, and game consoles. DVD players may be connected via composite video connectors although a higher bandwidth connection is recommended.
S-Video connections offer better quality than composite video. It uses a DIN jack.
SCART connections generally offer the best quality video at standard-definition, due to the use of pure RGB signalling (although composite and S-Video may alternatively be offered over a SCART connector). SCART provides video and audio in one connection.
Component video has become the best connection for analog video as higher definitions such as 720p
720p
720p is the shorthand name for 1280x720, a category of High-definition television video modes having a resolution of 1080 or 720p and a progressive scan...
have become common. The YPbPr
YPbPr
' is a color space used in video electronics, in particular in reference to component video cables. is the analog version of the YCBCR color space; the two are numerically equivalent, but YPBPR is designed for use in analog systems whereas YCBCR is intended for digital video. cables are also...
signalling provides a good compromise between resolution and colour definition.
HDMI is becoming common on AV receivers. It provides for the transmission of both audio and video. HDMI is relatively new technology and there are reported issues with devices not properly working with each other, especially cable/satellite boxes connected to a display through an AV receiver. Different levels of support are provided by receivers with HDMI connections. Some will only switch video and not provide for audio processing. Some will not handle multi-channel LPCM
LPCM
Linear pulse-code modulation is a method of encoding audio information digitally. The term also refers collectively to formats using this method of encoding...
. Multi-channel LPCM is a common way for Blu-ray and HD DVD
HD DVD
HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...
players to transmit the best possible audio.
Video conversion and upscaling
Some receivers can convert from one video format to another. This is commonly called upconversionVideo scaler
A video scaler is a device for converting video signals from one size or resolution to another: usually "upscaling" or "upconverting" a video signal from a low resolution to one of higher resolution A video scaler is a device for converting video signals from one size or resolution to another:...
or transcoding. A smaller number of receivers provide for de-interlacing
Line doubler
A line doubler is a device used to deinterlace video signals prior to display.The main function of a line doubler is to take an interlaced video source which consists of a two-field frame and create a progressive scan output. This can produce a brighter, smoother, higher-resolution picture...
of video signals. For example, a receiver with upconversion, deinterlacing and upscaling can take an interlaced composite signal at 480i
480i
480i is the shorthand name for a video mode, namely the US NTSC television system or digital television systems with the same characteristics. The i, which is sometimes uppercase, stands for interlaced, the 480 for a vertical frame resolution of 480 lines containing picture information; while NTSC...
(480 lines per frame sent as a field of 240 even numbered lines 0,2,4,8...478 followed by a field of 240 odd numbered lines 1,3,5,...479) and convert it to component video while also deinterlacing and upscaling it to a higher resolution such as 720p
720p
720p is the shorthand name for 1280x720, a category of High-definition television video modes having a resolution of 1080 or 720p and a progressive scan...
(720 lines per frame with all lines in normal sequence 0,1,2...719).
See also
- Digital media receiverDigital media receiverA digital media receiver , also commonly referred to as a media extender, media streamer, digital media hub, or digital media adapter , is a home entertainment device that can connect to a home network to retrieve digital media files from a personal computer or other networked media server and...
- Home Theatre
- Home Theater PCHome theater PCA Home Theater PC or Media Center appliance is a convergence device that combines some or all the capabilities of a personal computer with a software application that supports video, photo, music playback, and sometimes video recording functionality...
- AmplifierAmplifierGenerally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
- THXTHXTHX is a trade name of a high-fidelity audio/visual reproduction standard for movie theaters, screening rooms, home theaters, computer speakers, gaming consoles, and car audio systems. The current THX was created in 2001 when it spun off from Lucasfilm Ltd...