Home Theater Receiver functions & Components @ Home Theater

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Home Theater Receiver functions & Components

Get a Home Theater Receiver. A Home Theater Receiver combines a radio, preamp, and multi-channel amplifier into one package. Purchase a high-quality receiver, as it will greatly affect the sound quality of your home theater.

A Home Theater Receiver combines the functions of three components
1.Tuner
A tuner for AM/FM; in some cases, HD (High Definition Radio), XM or Sirius Satellite Radio,
and/or Internet Radio.

Receivers usually have a built in tuner for Amplitude Modulation (AM) and Frequency Modulation (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). Future models may drop radio features of all kinds in favor of support for MP3 players, and the normally used devices such as CD players, turntables, etc. as it may cut the cost of the devices. On the other hand, some higher-end models are moving in the other direction by adding HD Radio tuners.
2.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. Movie soundtracks have been provided via a number of encoded formats. The first common format was Dolby Pro Logic. This format contained a center channel and surround channel. These channels were mixed into the left and right channels using a process called matrixing. Receivers were produced with Dolby Pro Logic decoders which could separate out these two additional 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 less common format called DTS is present on some DVDs. Most AV receivers provide this decoder as well.

A number of other decoders may be provided by the AV receiver such as Dolby Digital EX, Dolby Pro Logic IIx, DTS Digital Surround, DTS-ES, DTS 96/24, and DTS Neo:6, and the newer blu-ray audio formats.
3.Amplification
Stereo receivers have two channel 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, center, left surround and right surround speaker to be powered by the receiver. 7.1 receivers 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.

Some receivers can convert from one video format to another. This is commonly called upconversion 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).

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