Also called AV receivers, it forms the central nervous system of a home theatre system. It contains all the processing and decoding to amplification required to bring your speakers to life via a 5.1 channel receiver or 7.1 channel configurations. It also is the central control hub for all your listening characteristics, room acoustics, speaker size etc. There are a number of models that come from quality manufacturers like, ONKYO, denon, Jamo etc. The channel speaks about front right and left, which normally carry the entire frequency spectrum using tower speaker systems (2) + front center (1) which deliver dialogues in the movie, + 2 side surround speakers which give the theatre effect of reflected sound or motion effect from the sides makes a simple 5 channel system. the 0.1 channel represents the subwoofer which delivers the lowest notes ranging from 20Hz to 200Hz. For a 6.1 channel it would also have additionally a central rear speaker. Now for pure no nonsense music enthusiasts this would be a little luxury and they can go for a 2 channel amplifier and 2 tower systems. Please see the speaker placement diagram here in various configurations depicted

• The first thing that captures you about an AV receiver are the logos on the front panel. While decoding surround sound formats is the most important role of a receiver, the types of formats to be decoded run aplenty. If you live in a small house or do not wish to invest in an elaborate 7.1 channel set up, dolby digital and dts would suite you just fine with a 5 speakers and a sub. THX is also regularly seen as an adornment and is useful for viewers of action or hindi films, which have a bright and a harsh sound. The newer dolbi pro logic II and dts neo formats work wonders with your older stereo or mono recordings. Spliting them over all 5 channels and breathing new life into them. An option definitely worth trying.
  
• An AV receiver, as the central hub of your entertainment, center must contain enough inputs for various sources of recording equipment. Your best bet would be to go with a receiver that has at least a couple of co-axial and optical digital inputs each, along with some kind of digital output too.
  
• Video connectivity is what differentiates an AV receiver from a traditional stereo receiver (which only handles 2 channels audio and no video) There are three types of video connections for consumer grade electronics: composite video (most common), S-video (better picture quality) and component video (best picture quality). All AV receivers will have composite input jacks for all types of video sources. But for higher quality video sources like DVS-Video and super VHS moderately priced AV receivers will have S-video input jacks. In this age of progressive scan DVD-Video and high-defenition TV (HDTV)signals, the component video connection offers the best picture quality and colour fidelity. It supports high defenition picture resolutions (Eg 1080i) and is required for progressive scan video. With any video connection, the receivers job is to simply switch among video sources and pass the signal with minimal degradation. In almost all cases, the receiver does not perform any processing on the video signals. One thing to keep in mind is that most receivers do not convert between different types of video connections except for the newer ONKYO receivers, which can convert composite video signals into S-video and pass them on to the monitor. The exception are some advanced AV receivers that are capable of syncing sound with picture if there is delay in one of them.

• Power ratings of receivers are played around with a lot and to ensure that you are not being cheated, check the brochure or the owners manual for correct listings. The power should be rated in 'continuous' terms and not 'peak'. Usually an 8 W rating is given but do not trust receivers, which have power ratings without any impedance values. All channels should be also rated simultaneously from 20-20000 Hz, the full spectrum of sound to be reproduced by a home theatre system. And lastly, the total harmonic distortion (THD) factor should not be ignored. This is a measure of how clean the receiver can amplify audio signals. If you enjoy music and movies at louder volumes than normal, pay extra attention to this specification. Typical values are 0.05% - 0.08%. THD for a clean receiver but any value below 0.1% is acceptable,. Do not compare THD values for receivers of different brands too closely since there are some slight variations as how this number is measured across different manufacturers.
  
• The amount of power you require for your home theatre needs will be dictated by the size of your room and your speakers. Check your speakers for their sensitivity specification. If it is anything below 87dB, you will need at least 100 RMS of amplification per channel to fill a room that is about 2500 ft3.