5.1 /  6 channel input: A group of six sockets at the rear of an AV amplifier which enables external decoders to be connected, thus future-proofing the design for potential new surround formats. 

Coaxial: A digital input found on many AV amplifiers. Connect it from the coaxial output on a suitable digital source such as a DVD player for Dolby Digital or DTS multi-channel audio or for easy connectivity from digital recorders such as a MiniDisc..

Component video: A picture signal format, superior to either composite or S-video types. Component video sources include many higher quality DVD players.

Composite video: A picture signal format. Still gives good results, but to benefit from the high resolution which DVD supports, use the S-video connections. Composite video signals are most commonly carried from a VCR to an amplifier along a scart to phono lead.

DAC: Digital to Analogue Converter. The system employed to convert digital data (1s and 0s) into analogue format.

Dolby Digital: A multi-channel sound format which is the standard in Europe and the most used in the world. This format can potentially support any number of channels: mono, stereo, 3 channel surround or 5.1 surround being the ones you will find most.

Dolby Pro Logic: An older format than Dolby Digital, which provides surround sound from a stereo signal. Although not offering the same level of separation or dynamics that Dolby Digital offers, Pro Logic soundtracks can be heard on a wide variety of pre-recorded videos and television broadcasts. All that you require is a NICAM stereo television or HiFi/NICAM audio VCR to be connected to your AV amplifier and when a Pro Logic programme is broadcast or played back you will be able to enjoy it with the surround sound activated.

Dolby Pro Logic II: Takes an existing 2 channel stereo sound and decodes a dynamic, full-bandwidth 5.1 soundtrack. A great improvement over original Pro Logic and very popular with both 2 channel sourced movies (eg stereo TV broadcasts and video-taped recordings) and music too.

Dolby Pro Logic IIx: The latest of the Pro Logic formats, IIx is capable of delivering a full-bandwidth, highly dynamic 7.1 surround sound from 2 channel stereo and 5.1 channel sources. 7.1 sound features an additional pair of rear-surround channels, on top of a 5.1 configuration.

Dolby Digital EX: Discrete 6.1 variation of Dolby Digital which is decoded from a true, discrete 6.1 Dolby Digital encoded soundtrack - an extra rear centre channel, on top of a 5.1 configuration.

Dolby Digital Matrix 6.1: Dolby Digital which delivers 6.1 sound from a 5.1 Dolby Digital signal, by processing and decoding an additional channel of information from the existing left and right rear channels, for a rear-centre channel.

DSP: Digital Sound/Signal Processing, designed to enhance the soundtrack of movies and music to recreate the ambience of a large cinema auditorium or music venue, without the need for additional speakers.

DTS: A multi-channel sound format capable of delivering superior sound to that of  Dolby Digital. All of the digital home cinema amplifiers on this site support both Dolby Digital and DTS.

DTS-ES: Discrete 6.1 variation of DTS which is decoded from a true, discrete 6.1 DTS encoded soundtrack

DTS Matrix 6.1: DTS which delivers 6.1 sound from a 5.1 DTS signal, by processing and decoding an additional channel of information from the existing left and right rear channels, for a rear-centre channel.

DTS Neo:6: Takes an existing 2 channel stereo sound and decodes a dynamic, full-bandwidth 5.1 soundtrack. Ideal with both 2 channel sourced movies (e.g. stereo TV broadcasts and video-taped recordings) and music too.

DTS 96/24: (96kHz sampling rate - compared to typical 48kHz sampling rate & 24-bit word length). DTS 96/24 decoding delivers superior fidelity audio from suitably encoded DVD discs.

EQ modes: Equaliser modes - preset or user-adjustable tone controls that give emphasis or reduce the emphasis on different parts of the frequency range. So different modes might improve bass or treble or midband, enabling a fine-tuning of the tone. In home-cinema amplifiers, equalisation is sometimes carried out as a default correction of spikes in the frequency range, built-in to some soundtracks which, whilst appropriate for a commercial cinema environment, are not for a home cinema system.

HDMI: High Definition Multimedia Interface - the new Scart. The HDMI connector is a digital interface which has global backing as the universal digital connector for home entertainment products. Capable of carrying a very large data rate, it can carry picture, sound and other information between the latest generation of DVD players, plasma screens, computers and more - with the best performance yet.

Headphone socket: Very useful for private listening. Many separates do not have their own independent headphone outputs, so having such a connection on your amplifier ensures that all components in your system can be heard through headphones.

Inputs: The more the merrier! When buying an amplifier you should consider the number of components you already own and those you intend to buy in future. Most AV amplifiers have three or four video inputs, one or two video loops and a couple more audio inputs. These can be used for most components excluding turntables. Turntables must be connected to a "phono" input. If there is no such input, a line level input can be converted into a phono type with the addition of an external phono pre-amplifier. Line level inputs include: CD, tuner, tape, video, aux, MiniDisc and DAT.

Also see Tape loop & Video loop.

Macro: A function found on more sophisticated learning remote controls which allows you to programme a sequence of events into one action. For example you can set up a macro to turn your television, VCR and amplifier on, switch to BBC1 and start the VCR recording - all at the touch of a single button!

Ohms: A measure of resistance. Amplifiers do not have a resistance, but they often quote optimal resistances which they can drive. For example an amplifier might quote an ideal speaker loading of 4 to 8 ohms. This means the amp can drive speakers which present average loads of between 4 and 8 ohms. See also Watts.

On screen display: This is a useful feature which home cinema amplifiers commonly incorporate. Setup and configuration information is overlaid on top of the picture you are currently viewing, enabling easy amplifier set-up. In addition, AV amplifier status (volume, DSP mode, input etc) can also be displayed. For this to work, you must take advantage of the amplifier's video switching. 

Optical: A digital input found on many AV amplifiers. Connect it from the optical output on a suitable digital source for Dolby Digital and DTS or for easy connectivity from digital recorders such as a MiniDisc.

Phono stage/input: The input specifically designated for turntables. Because record players have a much lower signal level compared to other components, amplifiers are often built with phono stages which have extra circuitry to compensate for this. Some amplifier's phono stages are switchable between "moving magnet" (MM) and "moving coil" (MC) type cartridges. The vast majority of turntables have MM cartridges fitted. Moving coil type cartridges tend to be pricier (typically from £100 upwards) and are usually custom fitted on more expensive turntables. All of the decks on this site have MM cartridges fitted unless we specifically state otherwise. AV amps with phono stages usually only have an MM input.

Pre outputs: Sockets which enable an external power amplifier to be connected, replacing the existing, built-in power amplifiers with those of a better quality and/or with greater power.

Record output selector: This is a very useful feature for those who make a lot of recordings or who wish to send a signal to another room. Sometimes you may wish to record from one source whilst listening to another. This switch enables you to do this without having to rewire your system each time or to connect the record output signal to a system in a different room, using the AV amplifier's video switching.

S video: Or Super Video. A picture signal format. Better than composite, but not as good as RGB. S video can also refer to a socket type (see below) which supports the signal, although an S-video signal can also be carried via a scart connection. To gain the benefit you will need a television with an S-video input (either a dedicated S-video type socket - see below - or a scart socket which supports an S-video signal).

Speaker outputs: Measured in pairs - i.e. one pair of speaker outputs will drive two speakers (left and right). Some amplifiers have two pairs of speaker outputs. It you wish independent control over two pairs of speakers, look for "switchable" speaker outputs so that you can turn each pair of speakers on and off separately. On top of this, AV amplifiers will have speaker outputs to connect to a centre and rear speakers or even two sets of the same. In the absence of switched outputs you could add a speaker switching box.

Tape loop: A tape loop is a group of two pairs of sockets; tape in (left and right) and tape out (left and right). Both are required to enable connection of a recording device (e.g. cassette recorder, MiniDisc recorder, DAT recorder) for playback and recording in stereo. For instance, if you have a cassette recorder and a MiniDisc recorder and wish to retain full functionality on both, you should buy an amplifier with two tape loops. If this isn't possible, we have a range of switching boxes which can convert one loop into two, three or even four!

Tape loops can also be used for connecting a graphic equalizer or add-on home cinema processor to an amplifier.

THX: is a specification of performance. Products with this badge are certified as having met certain stringent performance criteria as set out by Lucasfilm - George Lucas' film company. This is not to say that non-THX products are inferior (there are many products which would qualify but have not applied for the certification), but it is another guarantee of performance which is very desirable amongst home cinema enthusiasts.

For more information visit the THX homepage.

Video loop: Similar to a tape loop, but built for a VCR. Like other recording devices, a VCR requires output sockets for a record signal and input sockets for the playback signal. Video loops also include "video in" and "video out" sockets - two composite video phono sockets. If you wish to connect more then one VCR to your AV amplifier, then you will require more then one video loop.

Video Switching: A very handy way of connecting several video sources into your AV amplifier and using it to switch between the different signals it sends to your television, using only one or two inputs on your set for many devices, without having to rewire all the time. 

Watts: A measure of power - the higher the wattage, the greater the power of the amplifier. Wattages are measured into a load - that is to say that the figure is dependant on the speakers the amplifier is driving. An amplifier that outputs 50 watts into 8 ohm speakers, will output 100 watts into 4 ohm speakers as they have half the resistance. All amplifier ratings quoted on this site are into an average 8 ohm load except where specified. This is because, typically, the average speakers’ load is 8 ohms.

Contrary to popular belief, it is easier to damage speakers with an underpowered amplifier than an overpowered amplifier. Every amplifier has a point at which it runs out of power. At this point it wont get louder, instead the sound will harden up and distort - this noise is often referred to as "clipping" and is produced by the amplifier, not the speakers. However it is this "clipping" which most commonly damages speakers and leads to "blown" speaker drivers.