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See Videotape.

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Seen on CD cases, meaning the music was recorded and mastered in analog form - the first two As - but stored digitally (on the CD).

See also ADD, and DDD.

AC-3 (Dolby Digital):

Alternate name for Dolby Digital.

See Surround Sound, and Dolby Digital.


Music recorded in analog form (A), mastered or remastered digitally (D), and stored digitally on CD (the third D).

See also AAD, and DDD.


Adjustment of a record-player cartridge relative to the groove on the disc. Bad alignment causes distortion. Tape heads also need alignment, but it's best left to the experts.


Boosts signals to drive speakers. Can be one-box (integrated) or have separate pre and power sections.

The word amplifier in home audio is kind of a catchall term that could refer to a few different components. The following provide explanations of the main three types.


A preamp, in simplest terms, is an input selector and a volume control. This component serves as the control center for your entire stereo system. All the audio (and for those models with A/V switching, video) outputs go into the preamp where you can switch between them, adjust the volume (and tone controls, if present), etc. The preamp can also hold the audio processors (such as surround decoders) and some even included an integrated tuner. The preamp only works with signals at the line level (unamplified) and is used in conjunction with a power amp to bring the signal to full power to drive the speakers.

Power Amplifiers:

Power amplifiers do exactly what they say, amplify the signal. A power amp takes in the unamplified (line audio) signal from the preamp and increases the amplitude (volume) in order to drive the speakers. Most amplifiers are solid state (either transformers or transistors), but some manufacturers continue to make vacuumed-tube based amplifiers. Power amps may be designed to amplify a single channel (often referred to as a monoblock), two channels, or enough to power an entire surround sound system (usually 5 or six channels). Amplifier power is rated in Watts (W) and can range from lows below 30W to well over 150W.

Integrated Amplifiers:

An integrated amplifier combines a preamp and a power amp into a single component. These units' profile in the mainstream have dimmed in the shadow of receivers, but are still available and provide excellent performance if you're looking for good quality and a minimum of frills.

See also Tuners, and Receivers.


LPs/cassette tapes store audio in non-digital form directly related to the signal. Normal TV, FM, and AM signals are broadcast in analog form as well.


Applied to arms on turntables to prevent them from swerving towards the center.

ATV (Advanced Television):

Term given to the US digital HDTV system. Video is MPEG-2 encoded and audio is Dolby AC-3. Since there is no set standard for video resolution, the system currently supports multiple video resolutions. The system is still being deployed and it'll be a long time before ATV bumps off NTSC.

Audio Cassette:

The old standby for audio recording and playback. While it may not provide the best quality audio (analog recording), it is cheap, rugged, and can hold a fair amount of music (over 100 minutes on one side). A useful feature on cassette players are Dolby Noise reduction (B, C, and S) which help to reduce any unwanted noise or hiss in the recording.

See also Compact Disc, DAT (Digital Audio Tape), MiniDisc, and DCC (Digital Compact Cassette).


Stands for audio-visual.

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Balanced connections:

Positive and negative wires are shielded (for better interference rejection) in balanced connections. Normal connections use the negative to shield the positive cable. Use a three-pin XLR type plug to connect from the amplifier - also used in the AES/EBU digital format.


Low frequencies, often tricky to reproduce. Bass is very much the "Boom-Boom" in audio. The ideal is good bass extension (i.e. low down) allied to speed and rhythm.

Bass reflex:

A speaker design using airflow from a port in the cabinet to help low frequencies.


See Blu-ray Disc.


See Videotape.

Betacam SP:

See Videotape.


A separate amp channel drives each drive unit of a speaker, so a pair of two-way speakers needs two stereo amps, and two runs of cable to each speaker.

See biwiring.

Binding post:

Speaker terminal with threaded collar for gripping bare wires and sometimes a socket for banana plugs, too.


A single piece of digital information, basically an 'on/off' signal. Digital-to-analog converters turn strings of bits into audio signals.

Bit stream:

One method of turning digital CD data into analog signals. Bit stream digital-to-analog converters process single bits of digital data much faster than multibit DACs, which work on chunks of digital data.


Biwiring gives some of the benefits of biamping but at a lower cost. You need speakers with two sets of inputs and a split crossover, then send twin runs of cable from amp to each speaker.


See Blu-ray Disc.

Blu-ray Disc:

Blu-ray or BD.

Blu-ray Disc is an optical disc storage media format. Its main uses are high-definition video and data storage. The disc has the same dimensions as a standard DVD or CD. The name Blu-ray Disc is derived from the blue laser used to read and write this type of disc. Because of its shorter wavelength (405 nm), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser. A dual layer Blu-ray Disc can store 50 GB, almost six times the capacity of a dual layer DVD.

See also The Television, Videotape, LaserDisc, DVD, HDTV, and Satellite TV.


Increasing power by connecting a stereo power amp for use in mono, then adding a second bridged-stereo amp for the other channel. Power typically triples, but the amps must be designed to be bridged in the first place.

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Cable TV:

Multi-channel TV downs a wire to your home eliminating the need for an antenna or satellite dish. You pay for different combinations of services.


Copper conductors are mostly used with purity expressed as a number of 'nines'. So 'six nines' or '6N' purity might be 99.99997 per cent pure copper. Good speaker cables can have many strands (multi strand) or one or more thick wires (solid core). Look for arrows, which should point from the amp to the speaker, on directional cables. Directional interconnects have arrows that point from source to amp.


The device which actually plays the record. It converts the wobbles in the record's groove into electrical signals for your amp.

See also moving magnet, and moving coil.

Cassettes and Compact Discs:

See Audio Cassette, Compact Disc, DAT (Digital Audio Tape), MiniDisc, and DCC (Digital Compact Cassette).

CAV (Constant Angular Velocity):

LaserDiscs using the CAV (Constant Angular Velocity) process produces the highest quality picture and allows for perfect video freeze frames when paused (instead of a blue screen) and slow motion playback. CAV only allows 30 minutes of playback per side so it tends to be the lesser used of the two formats.


See Compact Disc.


Compact Disc-Digital Audio. Jointly developed by Philips and Sony and launched in October, 1982, CD-DA was the first incarnation of the compact disc, used to digitally record and play back music. The standard under which CD-DA discs are recorded is known as the Red Book.

See also Red Book.


CD-Recordable. Uses a special blank disc in a recording CD player. Once recorded it can't be erased, but plays in standard CD players when 'burned'. CD-R discs look green. Comes in two flavors, professional and consumer. Discs and machines are not interchangeable.


Compact Disc-Read Only Memory. A standard for compact disc to be used as digital memory media for personal computers. Uses CD as a Read Only Memory for computers. Vast storage capacity - around 600MB - on single disc. The specifications for CD-ROM were first defined in the Yellow Book.

See also Yellow Book.

CD Text (CD-text):

System that allows CD players to display a limited amount of text such as tracks names or lyrics. Introduced by Sony.

CD Text is an audio CD format in which up to 5000 characters of disc information (title, artist, song titles, etc.) is written into the disc Table of Contents. This information is displayed when the disc is played back on CD Text-enabled players.

See also SACD Text.

Class A Amplifier:

Amp in which positive and negative half cycles are amplified together. Runs hot, as the transistors in the power amp are on all the time, but has high sound quality.

Class B Amplifier:

Positive and negative halves of the signal dealt with by different parts of the circuit, the output devices switching continually. Runs cooler, but the sound is not as pure.

CLV (Constant Linear Velocity):

CLV (Constant Linear Velocity) LaserDiscs allow 60 minutes of playback per side (compared to CAV's 30 minutes) so it tends to be the more commonly used of the two formats. The downside to CLV is that it doesn't allow the extra pausing functions that CAV does.


A shift away from the natural rendition of music. Coloration is undesirable - 'boomy' bass, a 'nasal' midband or a splashy treble, for instance. All coloration gets in the way of the music.

Compact Disc:


Standard 5 inch (12cm) disc or the 3 inch disc (seldom seen), which stores information digitally, read by laser optical system. Originally designed for music storage the CD is now used for many applications (CD-R, CD-ROM, and CD-text). CD players cover all ends of the pricing scale and carry a variety of features. You can get portable CD players, single drawer units, and CD changers (multiple CD players). You can even purchase a CD-R system for your home Hi-Fi to record audio CD-Rs.

See also Audio Cassette, DAT (Digital Audio Tape), MiniDisc, and DCC (Digital Compact Cassette).

Compact Disc Digital Audio:

Seen on CD (Compact Disc) cases, meaning that the CD contains digitally stored sound (music) and can be played in standard CD players.

See also Compact Disc.

Compact Discs and Cassettes:

See Audio Cassette, Compact Disc, DAT (Digital Audio Tape), MiniDisc, and DCC (Digital Compact Cassette).


Definition 1 - In digital terms, this is a way to reduce the amount of storage space needed to reproduce a piece of information accurately. Several compression standards have been created by MPEG for various tasks such as compression digital audio (MP3) or video (MPEG-2).

Definition 2 - Used by radio stations to reduce level differences between loud and soft parts of music. Helps in-car and transistor sound but can be awful through a hi-fi tuner.

Constant Angular Velocity:

See CAV.

Constant Linear Velocity:

See CLV.


See Speakers.

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Digital Audio Broadcasting: digital stereo on both FM and AM. Very limited markets and no tuners yet out.


Digital-to-Analog Converter, turning on/off pulses into analog sound. CD players have DACs built in. Separate DACs can upgrade a CD player or other digital player/recorder, or can be used with dedicated CD transports.


Digital Audio Tape. A digital recording system now used mainly professionally. Uses a revolving recording head similar to that used in a VCR to record high quality digital audio. When DAT arrived, it promised CD-Quality audio on a recordable medium. DAT delivered on its promise, but its high price kept it out of the mainstream. DAT still exists, but most players are marketed towards the professional market such as recording studios and radio stations.

See also Audio Cassette, Compact Disc, MiniDisc, and DCC (Digital Compact Cassette).

Data Compression/Reduction:

Lowers the amount of data needed to store music. Sony's MiniDisc uses an in-house system called ATRAC (Adaptive Transform Acoustic Coding) while the PASC (Precision Adaptive Sub-band Coding) used in Philips' DCC format serves a similar function, removing signals its designers think you can't hear.

See also MiniDisc, and DCC (Digital Compact Cassette).


See Decibel.


Digital Compact Cassette. Philips' home digital tape system that records digital audio on a conventional audio cassette. Most DCC players could also handle standard analog cassettes as well. Alas these players have become rather hard to find, as the technology wasn't really accepted by the mainstream.

See also Audio Cassette, Compact Disc, DAT (Digital Audio Tape), MiniDisc, and Data Compression/Reduction.


On CD cases - music recorded and mastered digitally and stored digitally on CD.

See also AAD, and ADD.

Decibel (dB):

Measures changes in sound pressure. A change of 1dB is just about audible, while +10dB sounds like the level has been doubled.


Method of storing data used by CD players, DAT, DCC, MiniDisc etc. The sound or picture is converted to a stream of digits - effectively 1s and 0s representing on/off pulses.

Digital Audio Tape:

See DAT.

Digital Compact Cassette:

See DCC.

Digital output:

Allows the digital signal to be recorded or processed by an offboard DAC. Electrical or optical (fiber optic) outputs are provided.

Digital Satellite System:

See DSS.

Digital Versatile Disc:

See DVD.

Digital Video Disc:

See DVD.


Unwanted signals or signal changes added by equipment.


In a nutshell, Divx is Pay-Per-View DVDs. It's an alternative to rental, but you keep the disc - if you rewatch, your DVD player rings DIVX headquarters by phone and charges your account. Needs a Divx capable DVD player to work. This system did not prove to be popular and was abandoned in 1999.

Dolby B, C, and S:

Noise-reduction to boost quiet signals when recording and reduce them on playback, cutting hiss.

Dolby C:

See Dolby B, C, and S.

See also Surround Sound.

Dolby Digital (AC-3):

Also known as AC-3, this is the latest home theater sound system from Dolby, using five discrete channels of digital sound plus a separate subwoofer channel.

See Surround Sound.

Dolby HX Pro:

Not noise reduction, but a way to record more high frequency information without distortion (often called 'increasing headroom').

See also Surround Sound.

Dolby Labs:

Developed noise-reduction and cinema surround systems.

Dolby Pro-Logic:

Uses an extra center speaker at the front, which locks dialog to the screen. 4-channel system.

See Surround Sound.

Dolby S:

See Dolby B, C, and S.

See also Surround Sound.

Dolby Surround:

Encodes sound for rear effects channels into the stereo tracks. Needs to be replayed through a decoder to produce surround. 3-channel system.

See Surround Sound.


Momentary loss of signal during tape recording or playback from a defect in the magnetic coating or from the tape briefly losing head contact. Drop-outs can also occur on CDs, but it takes fairly serious disc damage.


Digital Satellite System. These satellite systems use a dish 18 inches in diameter and receive digital TV signals, which you can watch on your TV.

See also Satellite TV.


Discrete-channel home cinema digital sound system - rival to Dolby Digital.

See Surround Sound.

Dual Mono:

Some amplifiers are designed to keep the left and right signals separate throughout the amp - this helps avoid possible interference between the two channels.


Digital Versatile Disc (formerly Digital Video Disc).

Video Designed for home entertainment. They play on consumer DVD players that plug into TV sets or on desktop PCs equipped with a DVD-ROM drive and the requisite hardware/software. DVDs look like a standard CD, but hold several times the information.

DVD is the next step in digital video after the LaserDisc. Unlike a laserdisc, which digitally encodes the analog picture signal, the DVD's picture information is digital from the start and is compressed using the MPEG-2 standard. This allows a DVD to produce picture quality that rivals laserdisc, yet takes up less space on the disc. The digital format also allows for multiple audio tracks and other special interactive features not available on other formats like VHS or laserdisc.

DVD's popularity has been increasing since its introduction. It has just about caused the extinction of the laserdisc market in the US thanks to its cheaper cost, but there are far more titles available on VHS than on DVD.

Some DVD's have been protected by the manufacturer so they only can be played in a specific region of the world with the correct setting of the DVD region code in the actual DVD player where the region code will be pre-set to the region where you buy the equipment.

DVD region codes:

  1. The whole World (No restrictions).
  2. USA, Canada.
  3. Europe, Near East, South Africa, Japan.
  4. South East Asia.
  5. Australia, Middle & South America.
  6. Africa, Asia, Eastern Europe.
  7. People's Republic of China.

See also The Television, Videotape, LaserDisc, Blu-ray Disc, HDTV, and Satellite TV.

DVD Audio:

The specification for DVD Audio. It is thought the standard will be based around 24 bit/96kHz sampling. Some audio-only discs have already been produced using the DVD Video standard.


This is a version of a computer DVD that is erasable and can be rewritten. The specification for DVD RAM enables users to store 2.6Gb on a single-sided disc and 5.2Gb on a double-sided disc.

DVD region code:

See DVD.


This is a type of DVD that allows once-only recording of data. DVD-R discs will store 3.95GB on a single-sided disc, and 7.9GB on a double-sided disc.


The DVD version of a CD-ROM. Read by DVD-ROM drives installed in PCs, DVD-ROM discs exist in various capacities from one-sided single-layer (4.7GB) to dual-layer, dual side (17GB).


A 3GB erasable and rewriteable format under development by Sony, Philips and Hewlett-Packard as an alternative to the DVD RAM storage format. Sony is also developing a 12GB DVD-RW disc that will give five hours of TV recording, and predicts this will be available in two years.

See also DVD RAM.


See Videotape.

Dynamic range:

The range, in dB, between the largest and smallest signals reproduced by hi-fi.

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Speaker technology that uses the force of high voltages to push and pull a thin light diaphragm, which produces the sound.


An EP (Extended Play) is an extended playing phonograph record designed to be played at 45 revolutions per minute that plays a longer time than the standard 45 r.p.m. record on a Phonograph.

See also Single, LP, Phonograph record, and Phonograph.

Extended Play (phonograph) record:

See EP.

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Rapid speed instability on tape or vinyl leading to fluctuations in pitch. This is caused by transport problems.


Measured in Hertz (Hz). High-pitched sounds have a high frequency, low-pitched ones a low frequency. Audible sounds range from around 16Hz to 20kHz.

Front end:

The signal source in a system, e.g. LP or CD. Also the stage in a tuner which handles signals from the antenna.

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High Definition Compatible Digital - a coding system for CD which aims to get better sound. Needs a decoder to hear the full effects.


HDTV (High Definition Television) is a high resolution TV system developed in the 1980's. HDTV comes in many different forms, both analog (seen in Japan) and digital (in the US as ATV). It's a high-end system, but sees little use as most countries continue to use existing video standards like NTSC, PAL or SECAM.

HDTV promises to be the next great step in television by providing vastly superior picture quality to that of the existing NTSC/PAL standards. The generic definition for HDTV is a super high quality picture, but the details of the system vary from country to country. Japan has had HDTV since the late 1980's and utilizes a high quality analog signal. The US is in the process of phasing in the ATV standard which is based on a digital signal that produces a high quality signal, yet uses less bandwidth than NTSC. ATV signals are making their way into the major US markets, but it will be a while before ATV signals are everywhere. While ATV has a lot to promise (excellent picture quality, widescreen format, digital audio, etc.) it has a lot of hurdles to overcome.

HDTV TV sets are not cheap (costing well over a thousand dollars) and if you're looking for a small one (27" or smaller), forget it. ATV is also incompatible with all your existing NTSC video equipment (TVs, VCRs, DVDs, etc.) so if you want to get into the game, you have to buy all new video hardware. And even if you do take the plunge, there may be nothing to watch. Only a few of the top markets (LA, New York, Chicago, Boston, etc.) are starting to broadcast in HDTV. It'll be a while before TV stations everywhere will be offering ATV signals. Also, virtually none of the cable companies have signed on to the new technology.

Another issue that has yet to be resolved is the video standard. The FCC never imposed a definitive ATV video standard so there are a varying numbers of resolutions available, some not much better than NTSC. No agreement could be made so it'll be up to the market to decide which formats will survive and possibly leaving a lot of early adopters out in the cold. HDTV is an emerging standard but whether or not it will be able to displace NTSC in the marketplace (even with a government mandate) has yet to bee seen. For the time being, this is a format to approach with caution. NTSC has been with us for decades and attempting to change over to a new format is going to take a long time.

See also The Television, Videotape, LaserDisc, DVD, Blu-ray Disc, and Satellite TV.

Hertz (Hz):

Unit of frequency. One Hz means a signal has one cycle per second.


See Videotape.


See High fidelity.

High Definition Compatible Digital:


High Definition Television:


High fidelity:

High fidelity (hi-fi) or high-fidelity. Electronic system sound reproduction over the full range of audible frequencies with very little distortion of the original signal.

Home Theater:

See Speakers.

Horn loading:

Improves a drive unit's efficiency and output, using a structure within the speaker shaped like a horn. Works like the trumpet on an old-fashioned gramophone.


See Hertz.

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Electrical property. Low impedance draws a high current flow from the source, while high impedance draws a little. This means that speakers with a low impedance (lower than 6-8ohms) are more difficult for an amplifier to drive.

Integrated Amplifiers:

See Amplifiers.

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A LaserDisc (LD) is one of the first mainstream digital video systems. Laserdisc technology is similar to a CD, but stores information on a double sided optical disc roughly 12 inches in diameter (the size of a LP). A LD holds one to two hours of video depending on the mastering method used (CAV or CLV). LDs digitally encode the analog video and audio tracks to provide picture and sound quality far superior to VHS. Most current LDs also provide a digital audio track for AC-3 or DTS surround sound signals. For many years, a laserdisc player was the top option for playing movies on a home theater system. Unfortunately, the high price of laserdiscs when compared to videotape relegated it to a high-end market. LDs are rapidly loosing ground to DVDs in the US, but are holding their own in other countries like Japan.

See also The Television, Videotape, DVD, Blu-ray Disc, HDTV, and Satellite TV.


See LaserDisc.

Line level:

Describes inputs to amplifiers, which don't need amplifying before the amp can use them. Essentially an unamplified audio signal.

Long Play (phonograph) record:

See LP.


See Speakers.


A LP (Long Play) is a long-playing phonograph record designed to be played at 33 1/3 revolutions per minute (r.p.m.) on a Phonograph.

See also Single, EP, Phonograph record, and Phonograph.

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Frequency range where most of the instruments and voices are heard. Vital if singers, etc, are to sound natural.


See Speakers.


Sony's 64mm disc that can record up to 74 minutes of sound. Looks like a mini computer disc but works optically, like CD, on prerecorded discs, or magneto-optically in the case of blank software. It's making its way into the marketplace, but it's a very slow progression.

See also Audio Cassette, Compact Disc, DAT (Digital Audio Tape), DCC (Digital Compact Cassette), and Data Compression/Reduction.


See Mono.


Monaural (by shortening). Stands also for monophonic. Of or pertaining to a sound-reproducing system that produces a single output signal from one or more input signals.

See also Stereophonic.


An independent mono power amp, so two are required for a stereo system. Advantage is a lack of interaction between channels.


See Mono.

Motion Picture Expert Group:


Moving Coil:

Cartridges with a stylus connected to coils that move in relation to fixed magnets, creating electrical signals. Lower output than moving magnet.

Moving magnet:

Record-playing cartridge (pickup) design in which a tiny magnet connected to the stylus moves relative to a fixed coil in the body, thus generating the signal.


MP3 is a compression standard created by MPEG for compression digital audio.

See also Compression.


The organization MPEG (Motion Picture Expert Group) is responsible for various video and audio compression standards.


MPEG-2 is a compression standard created by MPEG for compression digital video.

See also Compression.

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CD-quality digital stereo television sound transmitted alongside the picture. Generally seen in European countries.


Video standard used in the United States, Canada, Japan, and other countries.

See also Video standards, PAL, and SECAM.

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Unit of resistance to current. Impedance of a speaker is measured in ohms - generally the lower the figure the harder it is to drive.


Used in DAC systems. Increases signal frequency, making it easier for conversion circuitry and ancillary systems to filter out unwanted signals.

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Video standard used in Australia, the UK, Denmark, and other countries.

See also Video standards, NTSC, and SECAM.


A circuit or component which does not amplify the signal. Introduces very little distortion.

Peak music power:


Phono stage:

Cartridges output signals at much lower levels than CD players and tape decks. Many amps have the extra amplification built-in, but increasing numbers don't, and require an add-on phono amplifier.


Any soundreproducing machine using records, whether cylinders or disks.

See also Phonograph record.

Phonograph record:

A Phonograph record is a record which normally today is in the shape of a disk made to be played on a Phonograph with 33 1/3 or 45 revolutions per minute (r.p.m.). Formerly also with 78 revolutions per minute (r.p.m.).

See also Single, EP, LP, and Phonograph.


Stands for peak music power, used on gear that needs to look more powerful than it is. If you see a boom-box advertising 160watts output, ignore it.

See also Watt.

Power Amplifiers:

Supplies audio signals to the loudspeakers.

See Amplifiers.

Power handling:

The maximum safe power for speakers. But be aware that it's easier to damage speakers with an amp of too low power driven hard, than with too much power.


The control part of an amp. Built into integrated amps, but can be separate and used with power amp or active speakers.

See Amplifiers.


See Dolby Pro-Logic, and Surround Sound.

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Radio Data System:

See RDS.


Data piggybacked on FM radio allowing RDS (Radio Data System) tuners to display the names of stations, and perform a range of station-seek and switching functions.


A receiver is the ultimate in one stop shopping. In a single box, you can get an AM/FM tuner, a preamp, an amp, and a surround sound decoder all at a reasonable price. Receivers have become an integral part of the surround sound craze because of their convince. Many receivers provide most of the necessary components for surround sound, namely the decoder (dts, AC-3, Pro-Logic, THX, etc.) and the necessary power amplifiers to drive all the surround channels. Some compromised do have to be made to fill all those electronics into a single box (specs still can't match separates), but they do provide good all around performance.

See also Amplifiers, and Tuners.


See Phonograph record.

Red Book:

The Philips/Sony specification for audio (CD-DA) compact discs.

See also CD-DA.

Region code (DVD):

See DVD.


The abbreviation r.p.m. stands for revolutions per minute.

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SACD Text:

Just like conventional CD TEXT, Super Audio CD includes a reserved area for recording text data. For discs that support text data, the Super Audio CD-player displays information such as disc title, artist name and track title for CD and Super Audio CD.

See also CD Text.

Sampling rate:

How fast a digital recorder or player samples a signal. CD, DCC and MiniDisc use a rate of 44.1kHz - i.e. 44,100 samples per second - while DAT recorders offer a choice of 48kHz or 44.1kHz, and Digital Audio Broadcasting will work on 32kHz. A digital-to-Analog converter needs to work on all three rates. The sampling rate determines the highest frequency recordable a digital system can carry - hence the development of higher-sampling formats, such as Pioneer's 96kHz system, for better treble extension.

Satellite TV:

Satellite TV started as a niche market. With the aid of a satellite dish, you could receive the network feeds that your local TV station and cable company used. While satellite TV offered a wealth of programming, it had its disadvantages. The C and Ku band dishes tended to be rather large (averaging 5-6 feet in diameter) so not everyone had room to put one in their yard. This all changed with the launch of the DSS system.

DSS was a whole new satellite TV system that used a small 18" satellite dish and a digital signal to give excellent audio and video quality. DSS has proven popular with people who didn't have room for an analog C or Ku band dish or wanted an alternative to cable TV.

See also The Television, Videotape, LaserDisc, DVD, Blu-ray Disc, HDTV, and DSS.


Video standard used in France and other countries.

See also Video standards, NTSC, and PAL.


Keeps a conductor or equipment away from interference.

Signal-to-Noise Ratio:

Describes the difference between the level of the audio signal and the level of unwanted noise. The larger the figure, measured in dB, the lower the noise will be.


A phonograph record, especially one revolving at 78 or 45 revolutions per minute (r.p.m.), having only one musical piece on each side.

See also EP, LP, Phonograph record, and Phonograph.


Here is some information on the various speaker types.

In the early days, there really wasn't much difference in speakers, but now there seems to be a great variety in speaker types.

First, a quick primer in speaker components:


This is a speaker that is designed to produce primarily the high end of the sound spectrum. They can come in various types such as a horn, dome, etc. but they all do the same thing.


Like the name says, the midrange produces sound in the mid part of the audio spectrum.


This is a speaker that is geared for the low end of the audio spectrum.


The subwoofer is a specialized woofer designed for the extreme low range of the audio spectrum and is seen a lot in home theater systems (not to mention those "boom-boom" car stereos). Subwoofers are often marketed as a standalone speaker.


Circuit inside the speaker, which splits high frequencies to the tweeter, low to the woofer, etc.

So when you go to buy a loudspeaker, it generally contains some of the speaker types listed above. Speakers can come in all shapes, sizes, and prices. They're usually based on a two or three-way design (i.e. using a tweeter or midrange in the speaker enclosure for a two-way design or a woofer, midrange, and tweeter in the speaker enclosure for a three-way design). Another thing to look for is the speaker's power rating. Speakers can handle a certain amount of power before they begin to distort and, if given too much power, self-destruct. Most manufacturers give a range of power (in Watts) that the speaker can comfortably handle.

As time went on, various classifications and specialized types of speakers came out. Here's a few of them:


This is your typical speaker. It can be a compact unit (such as a "bookshelf" unit) or a larger floorstanding unit. The general rule of thumb for speakers is that bigger is better (i.e. - the bigger the speaker, the better is its sound range) but modern engineering has taken a bit of steam out of that idea. It's possible to get some very impressive sound quality out of a small speaker. But the bigger units still have one advantage, bass. While the smaller, bookshelf, speakers can provide some very good sound quality, they generally can't match the bass response of a larger speaker which contains a dedicated bass driver (a 10 inch woofer for example).

Sub/Satellite System:

Popularized by the Bose Acoustimass system, the sub/sat system can be divided up into two parts. The compact satellite speakers which provide the high and midrange sounds and the subwoofer unit which handles the low end. This combination produces good full-range sound quality while maintaining a small footprint. This is handy if you don't have room for large speakers.

The one downside to this system is that speaker placement can be a very critical issue. If the satellite speakers are positioned too close to the listener, the system can often sound somewhat 'tinny' because the sound from the satellite speakers (which are carrying the high frequencies) comes through stronger than the sound coming out of the bass unit. Keeping the output balanced between the sub unit and the satellite units maintains proper audio quality.

Home Theater:

This introduced several new speaker classes in itself. The main speakers are similar to your average loudspeaker. The center channel speaker is geared towards the midrange since its main purpose is to reproduce the dialog in the movie. The surround speakers are designed for the rear channels and reproduce ambient noises in the movie's soundtrack and to help create that surround effect.

But remember this one piece of advice when going speaker shopping: Listen before you buy. After all, who wants to buy a speaker that sounds terrible?


See Surround Sound.


Stereophonic (by shortening). A system or the equipment for reproducing stereophonic sound. Of or noting a system of separately placed microphones or loudspeakers for imparting greater realism of sound, used especially with wide-screen motion pictures, high fidelity recordings, etc.

See also Mono.


See Stereo.

sub/sat system:

See Speakers.

Sub/Satellite System:

See Speakers.


A separate woofer box to produce the deep lows smaller speakers can't reach.

See Speakers.

Surround Sound:

Surround sound. It's that great buzzword out there that seems to be showing up on anything that has a speaker anymore. The surround sound field is becoming increasingly more complex as more and more surround standards emerge onto the scene. Dolby Surround, Pro-Logic, THX, AC-3 (Dolby Digital), SRS, and dts are just some of the many systems out there but what's the difference? Let's take a look at each of them...

Dolby Surround:

This might be considered the foundation of all surround sound systems. Surround sound's origins can be traced back to the movie theater, where more speakers were added in an attempt to "surround" you with sound and make you feel like you were actually in the picture. Many systems came and went over the years, but Dolby Laboratories eventually came up with the de facto standard. As home theater emerged, the surround sound system migrated from theater to living room as surround sound began appearing on home audio components.

Dolby surround is made up of three channels of audio - the left, right, and surround. The main left and right channels also produce a "phantom" center channel.

Dolby Pro-Logic:

Pro-Logic was the next step in the evolution of Dolby Surround. While the standard Dolby Surround is made up of three channels (left, right, and surround), Pro-Logic extracts a fourth channel of audio from the mix, the center channel, by using active decoding instead of the normal passive system. The center channel is used to enhance dialog clarity and to focus the listener's ear on sounds that are directed towards the center of the screen. This plugs the "sonic hole" that is left in standard Dolby Surround setups.


THX isn't so much a type of surround sound as it is a standard. THX works hand in hand with Dolby Surround to create the ultimate home theater. Movie audio tracks are mastered to be played in a large auditorium, which tend to have different acoustics than a typical living room. What the THX system does is compensates for this difference so what you hear in your living room sounds exactly the same as in the theater. This is accomplished by special circuitry in the THX processor, which takes the surround information and adjusts it to sound spatially and tonally correct in your listening room.

Audio equipment stamped with the THX logo meets guidelines set by LucasFilm for audio and video quality. These guidelines for quality began with movie theaters and have expanded out from there. THX has even set the bar for video mastering so you'll even find the THX stamp on VHS tapes, laserdiscs, and DVDs.

THX is fully compatible with Dolby Pro-Logic, Dolby AC-3 and dts and is a useful addition to all surround systems.

AC-3 (Dolby Digital):

The digital revolution caught up to surround sound with AC-3 (also knows as Dolby Digital). Dolby Digital goes beyond the four-channel Pro-Logic to create a digitally encoded system with 5.1 channels of audio (previous systems were mostly analog encodings). The surround channel is now in stereo along with the addition of a dedicated low frequency channel (the .1 in 5.1) which is used to drive a subwoofer. Another added bonus of the system is that the surround channels carry the full range of audio instead of just the mid-tones in earlier systems.


Another crossover from the movie theater. The dts system works very much like AC-3 in that's it's a digital 5.1 surround system but has its own traits that makes it unique. The main goal of dts is to provide the best possible audio from a digital recording.

The system made its debut in theaters with the release of Jurassic Park.


SRS tends to show up a lot on computers and TV sets nowadays. Sometimes it's hard to package a true surround sound system in something like a TV set. What SRS does is to simulate the surround sound effect to make it sound like you have surround sound when you only have just the two speakers in front of you.


See Videotape.

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Tape loop:

A pair of sockets on an amp letting the signal out for recording on a tape deck and another pair to let the signal back in for replay.

The Television:

In a home theater system, there obviously needs to be something to display the pictures and you standard TV (Television) can do the job just fine. A big screen TV is an excellent companion to the big sound that a home Hi-Fi can produce. Most people recommend at least a 27" TV when building a home theater. If you're working with a smaller room, a 20" set may work as well, but anything below that may feel a little awkward when you combine a tiny screen with movie theater class sound.

Most TV manufacturers nowadays have caught on to the home theater trend and are now adding additional audio-video inputs to the set. Front panel inputs are handy so if you want to hook something up in a hurry, you don't have to blindly grope around in the dark to find the auxiliary inputs in the back. The other advantage of these A/V inputs is that they can bypass the RF tuner section and give you better picture quality.

TVs come in several flavors nowadays as well. There's the conventional picture tube based set, which covers sizes up to about 40" diagonally. Sony has earned a high reputation for their Trinitron picture tubes. While CRT (cathode ray tube) technology really hasn't changed much since the invention of the color picture tube, it has been refined over the years. Current picture tubes produce a brighter, sharper, and flatter (causing less distortion produced by a curved screen) picture than ones made a few years back.

The second flavor is the projection screen. If you want a really big picture, this is the way to go. Rear projection TVs project onto a fixed screen from the rear. These TVs produce a big picture (over 40" diagonally) yet manage a reasonable footprint. The second types are the front projector units. An advantage of these is that you can make the screen just about as large as you want (it all depends on projector placement). While a good quality unit can give you that Movie Theater feel in your living room, these units can be expensive and finding a place for the projector can be a pain sometimes (these units can be a bit bulky, but they can be ceiling mounted to save space). Many projectors for computers can double for your home theater system. Many data projectors come with A/V inputs, which allow it to accept signals from your home video sources (VCR, DVD, etc.). Most of these units are fairly compact and provide excellent picture quality.

See also Videotape, LaserDisc, DVD, Blu-ray Disc, HDTV, and Satellite TV.


Developed by LucasFilm, this is basically a set of standards for home theater equipment along with some specialized sound processors. THX works hand in hand with other surround systems such as dts, AC-3 or Dolby Pro-Logic to provide the ultimate home theater sound.

See Surround Sound.


The device on a turntable which holds the cartridge.

Toroidal transformer:

Transformers bring mains voltages down to the levels required. Toroidal transformers (doughnut-shaped) get better stability and less flux leakage (magnetic radiation that can interfere with other circuits).


Short and sudden events in music (e.g. a cymbal crash). Difficult to reproduce.


High frequencies. When we say treble is splashy, it means cymbals, for example, sound like they're going 'tizzshsh', rather than having a crisp sting.


Like biamping and biwiring, but for three-way speakers. Need three runs of cable in the case of triwiring and three stereo amps if you want to triamp the speakers.


See Triamping/triwiring.

Tube/Vacuum Tube:

See Valve.


With the increasing popularity of receivers, separate tuners have become somewhat harder to find, but they haven't gone extinct yet. Most tuners have far better specifications than the AM/FM section of receivers because they're not forced to compromise. In a receiver, the tuner isn't sandwiched in the same box with other audio sections like surround decoders, preamps, and power amplifiers. The tuner section is often compromised in order to fit in everything else. A stand alone tuner, meanwhile, is a one trick pony and it does its trick well - receiving AM and FM radio. This performance advantage is useful if you have to deal with weak signals or adjacent channels.

See also Amplifiers, and Receivers.


See The Television, Videotape, LaserDisc, DVD, HDTV, and Satellite TV.


The speaker driver handling the treble.

See Speakers.

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Vacuum Tube:

See Valve.


Amplifying device: electrodes in a glass vacuum enclosure. Produces a warm, seductive sound. This was the main type of audio amplifier used before the advent of the transistor. Tubes are still used in some high-end audio equipment for their distinctive audio qualities.


Stands for Video Cassette Recorder.

See Videotape.


See Videotape.


See Videotape.


See The Television, Videotape, LaserDisc, DVD, HDTV, and Satellite TV.

Video standards:



The VCR (Video Cassette Recorder) has become the most popular item for recording and playing back video at home. Because of the growing popularity of home theater, most VCRs sold nowadays are Hi-Fi Stereo. Add a stereo VCR to you home Hi-Fi system and you've got yourself a home theater system.

A quick rundown on videotape standards:


VHS is pretty much the standard when it comes to videotapes. Just about any commercial tape you get is on VHS.


SVHS takes the VHS standard and improves on it by a slightly better recording method to produce better picture quality. While SVHS and VHS VCRs use the same tape, SVHS tapes are not compatible with VHS VCRs. However, many of the newer VHS VCRs have a feature called SVHS quasi playback which allows a VHS VCR to play a SVHS tape, but you don't get the improved picture quality.


DVHS and other Digital videotape formats are only starting out but make the claim of vastly improved picture quality by digitally encoding the picture information.


Essentially a VHS tape in a smaller case. VHS-C is used in camcorders and using a special holder, VHS-C tapes can be played in a standard VHS VCR.


Despite the claim of Beta being the better tape format, it lost out to VHS back in the 1980's and is seldom seen anymore.

Betacam SP:

While it resembles a Beta tape, Betacam SP is used in professional equipment.


8mm are another compact videotape format. Like VHS-C, it is used primarily in camcorders.


Hi-8 is an improved 8mm format that provides better picture quality than a normal 8mm tape.

See also The Television, LaserDisc, DVD, Blu-ray Disc, HDTV, and Satellite TV.

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Unit of power. More watts mean more power, but how loud a system sounds also depends on speaker sensitivity and room size.

See also PMPO.


See Wave files.

Wave files:

Wave (which have the extension .wav) are a standard Windows format for digital audio. When you copy ("extract") a track from an audio CD to hard disk, you will usually be copying it to a Wave file.

Wave files can have various qualities of sound depending on how they are created or saved, but the most common is 44,100 Hz, 16 Bit, stereo (the same standard as audio tracks on CD).


The length of a wave. Sound at 50Hz in air has a wavelength of around 6.9 meters.


The large drive unit in a speaker to produce bass frequencies.

See Speakers.


Slow variations in speed of a record or tape deck, making sustained notes sound unsteady.

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Yellow Book:

The book which sets out the standard developed by Philips and Sony for the physical format of compact discs to be used for information storage (CD-ROM).

See also CD-ROM.

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My Sources / Mine kilder

Sources: Various booklets and books, the Internet, and various encyclopedias.

Kilder: Forskellige brochurer og bøger, internettet og forskellige leksikoner.

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