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Home theater amplifiers boost the audio signal coming from a television, digital versatile disc (DVD) player, or another device so that it is loud enough to be reproduced by one or more speakers. Since home theaters come in many configurations, a variety of amps are available to support different audio setups. Generally, home theater amplifiers are classified according to their power outputs defined in watts, the number of audio channels they support, and any extra features they provide.
Typically, an amplifier's box or online product listing will specify the amount of power it is capable of producing in watts. This information is often listed in the product's name or featured prominently on the packaging. The number of watts listed denotes the loudness of the system, with higher values indicating higher levels of loudness. For large media rooms, it is often necessary to use an amp with a higher wattage, since the sound must be loud enough to travel some distance without losing too much power. The amplifier, however, must match the power rating of the speakers it is being connected to, to avoid damaging them.
In addition to varying power ratings, home theater amplifiers are usually classified according to the number of audio channels they support. A mono amplifier, which typically isn't used in the average home theater, supports a single audio channel and is commonly used by audiophiles to connect high-power subwoofers. Stereo amps provide two channels of audio: right and left. In general, a stereo amplifier is suitable for small rooms, or people who are looking for a simple audio system.
Home theater amplifiers that support more than two channels of audio are commonly referred to as multichannel or surround sound amps. Often, the number of channels listed features a '.1' at the end. For example, the number of channels might be listed as '5.1' or '7.1.' This number means that the amp provides a dedicated subwoofer output, while the preceding number specifies the number of speakers, other than the subwoofer, that the amplifier supports. Multichannel amps are commonly used to produce a more even and realistic audio signal throughout a home media room.
Some home theater amplifiers are built into other devices or provide additional features. It is fairly common for an amp to be housed in the same unit as an audio-visual receiver. This allows the audio from multiple devices, such as televisions and DVD players, to be connected, controlled, and amplified by a single device. Some amps also allow for increased control over the audio’s quality by providing equalization controls in addition to the typical volume control.