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


LPs/cassette tapes store audio in non-digital form directly related to the signal.


Applied to arms on turntables to counteract their tendency to swerving in towards the centre of the disc.

Bass reflex

A speaker design using air-flow from a port in the cabinet to help low frequencies.

A type of loudspeaker enclosure in which the woofer’s rear radiation is used to facilitate a smooth and extended low-range response through a tuned port.

Class A

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

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.


Digital-to-analogue converter, turning on/off pulses into analogue sound. CD players have DACs built in. Separate DACs can upgrade a CDplayer 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.


Digital Compact Cassette - Philips' home digital tape system, now rather knocked out by Sony's MiniDisc


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

Decibel (dB)

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

A logarithmic measurement of sound pressure, or relative intensity of sound.
0 dB is the threshold of hearing, 130 dB is the threshold of pain.


Unwanted signals or signal changes added by equipment.

Distortion refers to any deviation of sound from the original electrical signal being fed to the headphone. Distortion can manifest itself as a "buzz", "click", or "raspy" sound over the music. Distortion can also be a change in the tonal character of the music signal fed into the headphone resulting in a bass-heavy, overly thin sound or any combination of the tonal level of the sound that doesn't match the original signal.

Dolby 3 Stereo

In cinema sound amps, delivers the surround channel information through the front left and right speakers, while providing centre channel information.

Dolby B, C + S

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

Dolby Digital

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

Dolby Digital Surround EX

Development of Dolby Digital 5.1 surround audio that includes a “matrixed”™ centre-rear audio signal to provide additional surround envelopment. Requires a suitable decoder, with amplification, and either one or two additional centre rear speakers. See also THX Surround EX 

Dolby HX Pro

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

Dolby Pro-Logic

Uses an extra centre speaker at the front, which locks dialogue to the screen. Now mainly used when viewing material sourced from video tape or off-air broadcasts, or with older soundtracks on DVD lacking discrete surround channels.

Dolby Pro-Logic II

Enhanced version of the original Pro-Logic, with improved channel steering for an effect closer to that available from true Dolby Digital source material. Also capable of extremely good effects with stereo material when using the Music mode.

Dolby Surround

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

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.


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.

Dynamic range

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

Expressed in decibels, the range of signal amplitudes (from the loudest to the quietest) that can be reproduced effectively by a piece of equipment. With respect to amplifiers, this range is defined by inherent noise at low levels and by overload distortion at high levels. The higher the number the better the performance.


Speakers that use the force of high voltages to push and pull a thin light diaphragm, which produces the sound.


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


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, eg LP or CD. Also the stage in a tuner which handles signals from the aerial.


High Definition Compatible Digital - a coding system for CD which aims to get better sound. Needs a decoder to hear the full effects. Developed by Pacific Microsonics, now owned by Microsoft.

Hertz (Hz)

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


Electrical property. A low impedance draws a high current flow from the source, while a 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.

LED (Light Emitting Diode)

A solid state diode that glows when current is passed through it.

Line level

Describes inputs to amplifiers which don't need amplifying before the amp can use them.


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

Moving coil

Cartridges with a stylus connected to coils which 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.


MPEG 1, layer 3. The compression system used for downloading music files from the Internet to a PC or MP3 recording device. It reduces file sizes by a factor of 12 to enable faster downloads, but it's possible to code music at a number of data rates, from pretty good to definitely lo-fi. 


National Television System Committee - On televisions and video cassette recorders - Broadcasting system used in USA and other countries (525 lines, 60 Hz scan) 


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.


Phase Alternating Line - Television colour encoding system used in Aurope and other countries.


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

Means of calculating maximum audio power output of a product, quoted as both (or all) channels combined.

Power amplifier

Supplies audio signals to the loudspeakers.

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 then needs to be used with power amp or active speakers.


Simply, Red, Green and Blue - a video connection, usually on a Scart cable - in which the three colour components of the picture are carried separately. In order to make this connection you need a DVD player and TV with RGB-enabled Scart sockets - not all older models are. You'll also need a 21-pin Scart cable that's either fully wired - ie with all 21-pins connected at ends - or, if you're running the sound from your player through your hi-fi system, at least a cable with the correct video pins hooked up. Some dedicated RGB cables only have these video connections, leaving out the other Scart capabilities in the quest for better picture.


Root Mean Squared - A calculation giving the power yield of a sinewave electrical signal. Often used to represent the output power of an audio amplifier and quoted per channel at a given percentage of distortion. 


Mini-Din plug connection used to carry video signal between source and display, in which the brightness and colour components of the signal are transmitted separately. Opinion is divided whether this or a Scart connection gives the best picture quality.

Sampling rate

How fast a digital recorder or player samples a signal. CD, DCC and MiniDisc use a rate of 44.1kHz - ie 44,100 samples per second - while DATrecorders offer a choice of 48kHz or 44.1kHz, and Digital Audio Broadcasting will work on 32kHz. A digital-to-analogue 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.


SE-quential C-oleur A- M-emoire. Pronounced "Sea-Cam". Sequential colour with memory. The television standard for France, Eastern Europe, Russia, the former Soviet Republics and some countries in Africa. SECAM is 625 lines of resolution with a refresh rate of 50 Hz. SECAM refers to a type of video or television signal. 


aka Euroconnector or even in some very old cases Peritel. A 21-pin connection between audio-visual components, carrying sound, vision and other signals. An RGB Scart is held by many to give the best picture quality for most people hooking up a DVD player to a TV set. Not all Scart cables are fully-wired - some have only the basic picture and sound connections made, while others are designed to carry video only. For more on this see entry under RGB.

S/N Ratio

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.

Measured in decibels (dB), the difference in level between a signal (typically a standard level) and the residual noise of the playback component through which it is passed the larger the S/N number, the better.

SPL (Sound Pressure Level)

The measurement (in dB) of the loudness level, as measured by changes in the air pressure caused by sound waves.


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

Super Audio CD

Developed by Sony and Philips, SACD uses 1-bit Direct Stream Digital (DSD) recording technology. Most discs are dual layer, with a standard CD layer which will play on a conventional CD player and a second SACD layer for improved performance when replayed on a dedicated SACD machine. 

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 (eg 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.


The speaker driver handling the treble.


Amplifying device: electrodes in a glass vacuum enclosure. Produces a warm, seductive sound.


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


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


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


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




Bir Amfi, RMS değeri kadar kıymetlidir. Bu değer, ne kadar yüksek ise, o kadar kıymetlidir.


PMPO (Peak Music Power Output)

Görüldüğünden daha güçlü gösterilmek istenen bir değerdir. 160watts çıkış gibi bir şeyler yazıyor ise, uzak durun, sizleri kandırıyor, çünkü tüm çıkış toplamlarını yazıyorlar. Çıkış gücü, tek bir çıkış kanalını göstermelidir.


Watt (Elektrikde güç ifadesidir)

Harcanan güç dışında, operlöre iletilen güç olarak da kullanılır. Yani bir çıkış sesi/gürültüsü/ses yüksekliği anlamlarını da taşır. Genelde kullanılacak operlör, operlöre verilen gücün en az %10 fazla kaldırma kapasitesine sahip olmalıdır.


S/N Ratio (Signal-to-noise ratio)

Ses sinyalinin, istenmeyen ses (gürültü) sinyaline oranıdır.

S/N oranı büyüdükçe, cihazın değeri (fiatı) artar.