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Abbreviations and Acronyms

Advisor Audio Glossary

Note: Words in italics are defined elsewhere in the glossary.

AC (Alternating Current): The type of current available from the home power outlets in homes; it alternates direction sixty times a second (50-60Hz).

AC-3(audio coding 3) Dolby's digital audio data compression algorithm adopted for HDTV transmission and used in DVDs, laserdiscs and CDs for 5.1 multichannel home theater use. See: Dolby Digital. Competes with DTS Consumer. The terms AC-1 and AC-2 are other versions developed by Dolby for different applications.

Acoustic-Suspension: A type of Infinite-Baffle Speaker that uses the air pressure inside a sealed speaker box to control driver motion. It has no port or opening.

AM (amplitude modulation): A Band of radio Frequencies that carries information by changing the strength of the Signal. Most AM broadcasts are in Mono, but many stations are adding equipment to broadcast Stereo AM programs. An AM stereo Tuner is required to receive them in stereo.

Amplifier: A separate component, or a section built into an integrated component, that strengthens the electrical signal (increases its amplitude). A power amplifier must be connected to a preamplifier (or "control amplifier") to switch and process the sound signal. An integrated amplifier combines power amplifier and preamplifier functions in the same unit. A receiver adds an AM/FM tuner to the integrated-amplifier configuration.

Analog: Type of audio component or recording medium that operates with Signals whose waveforms are directly analogous to the sounds they represent; see Digital.

Antenna: A transducer of radio waves, a structure (usually a wire or rod) that receives and/or transmits radio or television broadcast Signals over the air and sends them to a Tuner for processing.

Automatic turntable: One that sets the stylus onto a Record to begin play and removes it at the end of play without the user having to touch the tonearm.

Autoreverse: A feature of some Cassette Decks that allows them to play or record both sides of a cassette without the user having to turn it over manually.

AUX (auxiliary): An input jack found on some Receivers, Integrated Amplifiers, and Preamplifiers that can be used to connect Source components such as a Compact Disc Player or a Cassette Deck but not Turntables, which require special Phono inputs.

Azimuth: The angle between the actual recorded information and the edge of the audio tape. While the azimuth angle is theoretically set at 90 degrees, azimuth often varies from one Tape Deck to another.

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Back-EMF(ElectroMotive Force): Occurrence in which a speaker driver continues moving, after the amplifier signal stops moving the voice coil back through the magnetic field and creating its own voltage which flows back to the amplifier and creates a flopping effect in the resulting sound.

Balance: A control found on some Receivers, Integrated Amplifiers, and Preamplifiers that changes the relative Volume of the left and right Channels.

Balanced: Balanced wiring refers to wiring with two conductors in addition to a wire shield.

Band: A particular segment of a Frequency spectrum. For example, a Graphic Equalizer may divide the audio Frequency spectrum into ten bands or more, with one control to adjust the relative Volume of each band. The AM and FM bands are distinct parts of the RF (Radio Frequency) spectrum.

Bass: The lower Frequencies in the audio spectrum, such as those produced by a string bass or bass guitar. An instrument producing bass tones vibrates air more slowly than one producing Treble tones.

Bass Reflex: A type of Speaker system that has an opening, called a Vent or Port, in its enclosure. The sounds produced by the backward motion of the bass Driver(s) is tuned, by the length and size of the opening to reinforce those produced by their forward motion, which come out of the front.

Belt Drive: A method of rotating the platter of a Turntable by means of a belt, usually made of rubber, that connects the turntable's motor to the platter.

Bi-Amplification: A technique in audio application where the high frequency drivers in a speaker are driven or powered separately from the low frequency drivers used in the same speaker through the use of dual binding posts, used to physically separate the crossover on the speakers and multiple amplifiers, one per driver. ex; one for bass one for treble on each speaker system.

Bias: A very high-Frequency Signal added to an audio signal being recorded on tape to reduce distortion. Type I (Normal or Ferric) tape requires less bias than Type II (Chrome or Chrome equivalent) or Type IV (Metal) tape.

Bridge: Amplification term used to describe a process whereby two channels of amplification are combined to operate as a single mono channel, by using the positive wave form from one channel and negative waveform of another channel.

Cantilever: The rod or tube in a Phono Cartridge that supports the Stylus, and transfers the stylus's motion to the signal-generating elements of the cartridge.

Capstan: A rotating shaft in a tape recorder that pulls the tape across the magnetic Heads. The tape usually travels between the capstan and the pinch roller. A dual-capstan machine has two capstans; see Closed-Loop.

Capture ratio: An important Specification for an FM tuner, it indicates the minimum ratio between the strengths of two FM Signals at the same Frequency that enables the tuner to suppress the weaker signal by 30 dB. Smaller numbers indicate better performance.

Cardioid: A heart-shaped polar response of a Microphone, with strong rejection signals arriving from the rear.

Cartridge, or Phono Cartridge: A small component mounted on the end of the Tonearm in a Turntable; it holds the Stylus, which vibrates in the Record groove. The cartridge converts the vibrations into a changing electrical current, or audio Signal.

Cassette: A kind of magnetic-tape cartridge containing two reels.

Cassette Deck: An Analog component that uses standard-size audio cassettes for recording and playback; also known as tape deck. Audio Signals are recorded onto, or played back from, the magnetic tape contained in the cassette; see Heads.

CD (Compact Disc): A 4.8-inch plastic coated, metalized disc that stores up to 75 minutes of Digitally recorded music. The non-recordable disc contains microscopic pits that are read by an optical laser pickup in a Compact Disc Player. Each microscopic pit contains digitally encoded audio information.

CD(compact disc) Player: A Digital audio component based on the PCM recording system that plays back Compact Discs. Unlike Turntables, which play back conventional vinyl Records, a CD player has no Stylus and therefore makes no contact with the disc. Instead, a laser mechanism optically reads information contained on the CD.

CD Video (CDV): A Compact Disc that combines up to twenty minutes of Digital audio with approximately five minutes of video. CDV's are gold colored to distinguish them from silver-colored, audio-only CD's.

Center Speaker See Dolby surround

Channel: A distinct path for an audio signal. Stereo signals consist of two channels, left and right, which are sent to left and right speakers (or headphones), respectively (see separation). A surround-sound system adds one or more additional channels, usually for the rear. Mono (or monophonic) signals have only one channel.

Closed-loop: A drive system used in tape decks in which the tape is pulled by dual capstans, one on either side of the heads, so the part of the tape being played or recorded is held taut and fully isolated from the hubs.

compliance: A measurement of how easily the stylus of a phono cartridge can be moved by the grooves of a record. A high-compliance cartridge has a more flexible stylus than a low compliance cartridge.

crossover, or crossover network: A circuit that divides lower-frequency sounds from higher-frequency sounds. Crossovers are used in speakers that have more than one driver. In a two-way speaker system, for instance, the crossover sends the low frequencies to the woofer and the high frequencies to the tweeter. Crossovers are also available as separate components for use in more elaborate systems.

crossover frequency or crossover point: In a crossover network, the frequency at which audio signals are divided so they can be routed to the appropriate driver (low frequencies to a woofer and high frequencies to a tweeter, for example).

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DAB (Digital Audio Broadcast) 1.The NRSC (National Radio Systems Committee) term for the next generation of digital radio broadcast. 2. Initials of the compiler of this Pro Audio Reference.

DAC (or D/A, digital-to-analog converter) The electronic component which converts digital bits of information into analog signals that can then be amplified and used to drive loudspeakers, etc. The DAC is the last link in the digital chain of signal processing. See Data Converter Bits.

damping: The application of mechanical resistance, such as a rubber or silicone material, to reduce the amplitude of a resonance.

Damping Factor:is a measure of a power amplifier's ability to control the back-emf motion of the loudspeaker cone after the signal disappears. The damping factor of a system is the ratio of the loudspeaker's nominal impedance to the total impedance driving it.

DAT (digital audio tape): A cassette that is about half the size of a standard audio cassette. The cassette shell houses a reel of magnetic tape that contains digitally encoded audio information.

DAT (digital audio tape) deck: A digital recording/playback component that is based on the PCM recording system. Digitally encoded audio information is recorded onto, and retrieved from, magnetic tape. DAT recorders use a transport mechanism similar to ones found in analog cassette decks.

Data Converter Bits The number of bits determines the data converter precision. The more bits available, the more precise the conversion, i.e., the closer the digital answer will be to the analog original. When an analog signal is sampled (at the sampling frequency), it is being sliced up into vertical pieces. Each vertical piece is then estimated as to its amplitude (How large is the audio signal at this instant?). This estimation process is the data converters job. It compares the original signal against its best estimate and chooses the closest answer. The more bits, the more choices the data converter has to choose from.

dB (decibel): The common unit used to measure the volume of sound or an electrical signal that represents sound (also called loudness or amplitude). The decibel is a logarithmic ratio of two power levels. When sound-pressure level (SPL) is measured in decibels, for example, a whisper is about 40 dB and a jet engine about 120 dB. The decibel scale is logarithmic, meaning that an increase of 10 dB represents a tenfold increase in power: it takes ten times as much energy to produce an SPL of 80 dB as one of 70 dB, even though 80 dB is subjectively only twice as loud as 70 dB. Doubling the power raises the SPL by about 3 dB; cutting the power in half reduces the volume about 3 dB. Doubling or halving the volume requires a change in SPL of about 10 dB.

dBf: One decibel referred to a standard power level of one femtowatt (one quadrillionth of a watt).

dbx: Ordinarily, a noise-reduction system-more precisely known as dbx II--developed by the dbx company and used in some cassette decks. This system reduces the dynamic range of the audio signal during recording, making the soft parts of the music louder and the loud parts softer. During playback, the processing is reversed, restoring the original dynamic range and reducing the noise added by the tape. The dbx I system is used in professional studio tape recorders. Another type of dbx noise reduction is used in the MTS stereo TV broadcasting system.

DC (direct current): Electricity that flows in one direction only; see Ac (alternating current).

de-emphasis: A form of equalization used in FM tuners that is complementary to a pre-emphasis used in transmission. The purpose is to improve the overall S/N ratio (signal-to-noise), while maintaining a uniform frequency response. Some compact discs also are processed with a frequency pre-emphasis; these discs automatically engage de-emphasis circuits in the player.

defeat: To bypass a signal-processing feature, removing it entirely from the circuit. Tone controls are sometimes accompanied by a tone-defeat switch, which enables the user to eliminate their effects without changing their settings, allowing easy comparisons of the sound with and without tone control modifications.

digital: A digit is a number, and digital components use numbers in some way. A digital tuner, for example, may only use numbers on its front-panel display, or it may use digital-synthesis tuning circuits for improved reception. Compact discs contain a pattern representing a series of binary numbers (strings of ones and zeros); a CD player converts these numbers into a continuously changing current that represents the sound of the master recording. Digital audio tape (DAT) recorders turn analog input signals into binary numbers and record these on tape; for playback, the numbers are read from the tape and converted into an analog signal.

dipole: A type of speaker that radiates as much sound from its rear as from its front.

dipole antenna: A type of antenna that receives radio broadcasts from two directions. A T-shaped, folded dipole antenna is often supplied when you buy a tuner or receiver.

direct-drive: A method of rotating a turntable platter by using the motor shaft as the platter spindle.

dispersion: The spread of a speaker's high-frequency output, measured in degrees.

distortion: An unwanted alteration in an audio signal; also see THD (total harmonic distortion), noise, and IM (intermodulation).

dither: Very low-level noise added to a signal being digitized to reduce the high-order distortion caused by quantizing very low-level audio signals. See quantization.

Dolby B and Dolby C: Noise-reduction (NR) systems designed and licensed by Dolby Laboratories for use in consumer tape recorders. They work by making the high sounds softer during recording and louder during playback. Dolby C is more effective than Dolby B, but Dolby B is more common.

Dolby Digital®Dolby's name for its format for the digital soundtrack system for motion picture playback. Utilizes their AC-3 system of digital compression. The signal is optically printed between the sprocket holes of the film. Available also on laser disc and DVD as well as satellite transmission. Dolby Digital may use any number of primary audio delivery and reproduction channels, from 1 to 5, and may include a separate bass-only effects channel. The designation "5.1" describes the complete channel format. Surround decoder systems with Dolby Digital automatically contain Dolby Pro Logic processing to ensure full compatibility with the many existing program soundtracks made with Dolby Surround encoding.

Dolby HX Pro: A special circuit for tape recorders--the HX stands for headroom extension--that lowers the amount of bias added during recording when the signal being recorded already has a lot of high frequencies. This allows high frequencies to be recorded at higher levels with less distortion.

Dolby Surround: A system developed for movie theaters, now available in add-on home components, and in some audio/video receivers, that adds two more audio channels (center, front and rear) to the ordinary right and left stereo channels. To derive the extra channels, a Dolby Surround decoder adds the left- and right-channel signals together for the center-front channel and subtracts them from each other for the rear channel, usually sent to two rear speakers.

Driver: Any individual speaker within a system, such as a woofer or tweeter.

Dubbing: The process of making a recording of another recording. A dubbing cassette deck can record from one tape in one transport to another in a second transport. Dubbing can be done with two single-transport decks or one dual-transport deck.

DVD: (Officially "DVD" does not stand for anything. It used to mean "digital versatile disc" - and before that it meant "digital video disc" also known as hdCD in Europe.) A 12-centimeter (4.72") compact disc (same size as audio CDs and CD-ROMs) that holds 10 times the information. Capable of holding full-length movies and a video game based on the movie, or a movie and its soundtrack, or two versions of the same movie - all in sophisticated discrete digital audio surround sound. The DVD standard specifies a laminated single-sided, single-layer disc holding 4.7 gigabytes, and 133 minutes of MPEG-2 compressed video and audio. It is backwards compatible, and expandable to two-layers holding 8.5 gigabytes. Ultimately two discs could be bounded together yielding two-sides, each with two-layers, for a total of 17 gigabytes. There are four main versions: DVD-Video, DVD-Audio, DVD-ROM, DVD-RAM/R-W.

Dynamic range: The difference, in decibels (dB), between the softest and the loudest possible sounds that a component can produce. Higher ratings are better because they indicate that the component can more accurately reproduce the full dynamics of recorded music that is played through it.

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Effective mass: A measurement of how a tonearm resists motion. Tonearms must move freely to follow the groove of a record, and lighter tonearms usually perform this task better than heavy ones.

Efficiency: The percentage of the electrical input power to a speaker that is converted to acoustic energy. Usually specified for speakers, an efficiency measurement can be helpful when matching an amplifier to a particular speaker. Speaker efficiency can range from a fraction of 1 percent to as much as 10 percent or more. Note that efficiency indicates nothing about sound quality, only quantity of acoustic energy for a given input power. A more common way of expressing speaker efficiency is sensitivity.

Electrostatic: Speakers and headphones that use a method of producing sound by moving a flat diaphragm suspended in a high-voltage electrical field.

Elliptical stylus: A stylus whose cross section, as seen from above, is an ellipse placed across the record groove. This type of stylus traces the finer high-frequency modulations of a record groove more accurately than a spherical stylus.

EQ (equalization): The process of changing the relative volume levels of different segments of the audio frequency spectrum to compensate for losses or distortion at some stage of recording or reproduction. For instance, the output from speakers can be equalized to compensate for room acoustics. Phono signals require a specific type of playback equalization because of the equalization built into the process of cutting a record.

Equalizer: A component, or part of a component, that is used to equalize (see EQ) an audio signal received from a source component by dividing the signal into various separately adjustable bands. The most common type is the graphic equalizer, which derives its name from the way its sliding controls make a rough graph of the selected frequency changes on its front panel.

Expander: A device used to restore natural dynamic range. This is achieved by counteracting the compression of dynamic range that occurs when recordings are made and when a signal is broadcast.

Filter: A circuit that removes or attenuates a specific part of an audio signal. An infrasonic filter removes low frequencies. Some cassette decks have MPX filters to remove the 19,000-Hz stereo pilot tone(carrier wave) from FM broadcasts. Tone controls and equalizers are adjustable filters.

Flutter: A wavering sound caused by abrupt changes in the speed of electromechanical components such as turntables and cassette decks. Expressed as a percentage of variation from the correct speed, flutter measurements are usually combined with wow measurements in a single wow-and-flutter (W&F) specification. Lower figures are better.

FM (frequency modulation): A type of radio broadcasting that carries audio information by changing the frequency of the broadcast signal. An FM station with a center frequency of 88.1 MHz will actually broadcast a signal that changes from slightly less than 88.1 MHz to slightly more according to the waveform being broadcast.

Frequency: How often something vibrates or changes. Sounds are vibrations and can be represented by electrical signals that change at different rates; a low-pitched sound is represented by a slowly changing current, while a high-pitched sound is represented by a quickly changing current. Frequency is measured in cycles per second(cps), or hertz (abbreviated Hz). Most people can hear notes as low as about 20 Hz and as high as 15,000 or 20,000 Hz. In radio, frequency refers to the wavelength of the carrier signal of the station, such as 88.1 MHz for an FM Station or 1,010 kHz for an AM station.

Frequency Balance: The relative volume of different segments of the audio frequency range, from low bass to high treble.

Frequency response: This important specification indicates how evenly a component reproduces different frequencies. A typical spec might be 20 to 20,000 Hz + 3 dB, which means that the component will reproduce sounds as low as 20 Hz and as high as 20,000 Hz, and all those in between, not more than 3 dB too loud or too soft. If a frequency-response specification does not include a tolerance (the plus-orminus decibel figure), it is essentially meaningless.

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Graphic Equalizer: see Equalizer.

Head amp: see MC (moving-coil).

heads: The parts of a tape deck that impose a magnetic pattern on a tape (for recording) or detect one that is already there (playback). Most audio decks also have another head for erasing tapes, or randomizing the magnetic pattern on the tape so that a new one can be recorded. The heads of analog recorders are stationary, but those of digital audio tape (DAT) recorders rotate like the helical heads in VCR's.

HX Pro: see Dolby HX Pro.

Hz (hertz): The standard unit of frequency, named after the German physicist Heinrich Hertz. Measurements in hertz represent cycles per second, that is, changes away from a basic state and back again. In audio, the basic state is defined either as ordinary air pressure (without sound) or its electrical equivalent (a zerolevel signal).

IF (intermediate frequency) rejection: The ability of a superheterodyne AM or FM tuner's IF circuits to reject external interference at the intermediate frequency.

Image Rejection: The ability of a tuner to ignore signals removed from the desired frequency by twice the intermediate frequency (10.7 MHz in home FM receivers, 455 kHz in home AM receivers.)

IM (intermodulation) distortion: When a two-tone test signal is used, distortion components appear at frequencies that are sums and differences of multiples of the input frequencies. Their magnitude is expressed as IM distortion, which is more distressing to the ear than THD (total harmonic distortion). As with all types of distortion, lower figures are better.

Impedance (imp): Measurement, in ohms, of the total opposition (resistance and reactance) that a component has to electrical power; usually found in discussions of speakers.

Infinite-baffle: A type of speaker where the back wave produced by the driver is prevented from interfering with the front wave, usually by placing the driver in a sealed enclosure. See acoustic-suspension.

Infrared: A part of the electromagnetic spectrum that is invisible to the human eye. Infrared frequencies are used by wireless remote controls to send signals to the components they control.

Infrasonic: waves or vibrations with frequencies below that of audible sound. Compare with subsonic - commonly used (erroneously) to mean infrasonic. (2) Referring to a filtering circuit designed to eliminate frequencies below that of musical notes(typicaly set at 15Hz).

Integrated amplifier: A component that performs the functions of both a preamplifier and a power amplifier.

Isolation: The separation between a structure and everything surrounding it; usually in reference to turntable tonearms and platters.

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kHz(kilohertz): 1,000 Hz.

LaserDisc: Pioneer's trademark for a laser-read videodisc system. (Other videodisc formats are no longer available in the U.S.) LaserDisc players are Similar to CD (compact disc) players, therefore combination units that play both kinds of discs as well as the new CD videos are available.

LCD (liquid-crystal display): A type of electronic readout that does not generate its own light and, therefore, uses very little power.

LED (light-emitting diode): An electronic readout that produces its own light.

Linear-tracking tonearm: A type of tonearm that moves in a straight line across the radius of a record; see pivoted tonearm.

Logic: In cassette decks, the ability to switch from one transport function, such as fast forward, to another, such as rewind, without first pressing the stop button; doing this in decks without logic controls can damage the tape. In a surround-sound system, logic circuits are used to process encoded signals.

Loudness Compensation: A form of equalization that progressively emphasizes low frequencies (and sometimes high frequencies) as volume is reduced. Loudness-compensation circuits, which appear in some preamplifiers and receivers, compensate for the human ear's loss of sensitivity as the sound level decreases.

Magnetic Cartridge: A phono cartridge that generates an audio signal from the relative motions of a magnetic field and a coil or coils. The output is proportionate to the velocity of the stylus motion. See MC (moving coil) and MM (moving magnet).

matrix: Circuits in surround-sound processors that can synthesize a rear channel for ambience even if the original recording consists only of left and right stereo channels.

MC (moving-coil): A type of phono cartridge in which the magnets are stationary and the coils where the signal is generated move in response to the motions of the stylus in the record groove. Some MC cartridges produce very little current, and their output must be amplified to standard levels by a "head amp" or pre-preamplifier before further processing by a phono-preamplifier section.

MHz (megahertz): One million Hz.

microphone: An electroacoustic pickup device that converts acoustical energy--such as live music or a voice --into an electrical signal that is essentially equivalent in shape and amplitude to the acoustical input.

Mid-bass: The segment of the audio frequency spectrum covering sounds produced in the upper bass and lower midrange region; special mid-bass drivers can be used to reproduce these frequencies.

Mid-range: The segment of the audio frequency spectrum between the bass and treble frequencies. The mid-range includes most voices and the fundamental tones produced by most musical instruments. Mid-range drivers reproduce sounds in this frequency range.

MM (moving magnet): The most common type of phonograph cartridge. A moving-magnet cartridge has magnets attached to the interior end of its cantilever. The stylus motion causes these magnets to move near coils of wire, generating an electric current representing the audio signal.

Mono (or Monophonic): An audio signal in which all the information is combined in one channel; also, a component that handles only one channel, such as a mono amplifier (used in pairs for stereo programs).

MPX (multiplex): A method of combining two or more signals into one. Some tape decks have an MPX filter that removes the 19,000 Hz pilot tone from stereo FM broadcasts.

MTS (multichannel television sound): The system devised by Zenith and dbx for stereo TV broadcasting in the United States. An MTS decoder, which may be built into an audio or video component, receives stereo broadcasts and produces stereo signals from them. See SAP.

multipath: A condition that occurs when a broadcast radio signal reaches the antenna over two or more paths of different lengths. The result is interference that causes distortion and a loss of stereo channel separation.

mV (millivolt): One thousandth of a volt.

µs (microsecond): One millionth of a second.

µV (microvolt): One millionth of a volt.

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Noise: An unwanted part of a processed signal that is not related to the original signal. Audio noise usually sounds like hiss.

NR (noise reduction): A system designed to reduce the noise added to an audio signal during recording. See dbx and Dolby.

ohm: The basic unit of impedance, resistance symbolized by the Greek letter Omega .

Output level: A measure of how strong a signal produced by a component is, usually in relation to the strength of the signal put into it.

Oversampling: A digital filtering technique used in some compact disc players. The 44.1-kHz signal from the CD is sampled at some multiple of that frequency (usually two or four times), which raises the frequencies of any spurious signals created by the digital recording process well above the audio range. The spurious signals are then removed by an analog filter with a gentle slope, which is said to cause fewer phase irregularities than the sharp-cutoff filter required when oversampling isn't used.

Passive Radiator: An unpowered speaker or transducer assembly that is placed instead of the port in an enclosure system to produce a more uniform sound wave. Also called a "drone cone" or "slave cone.""Auxiliary Bass Radiator".

PCM (pulse-code modulation): A system of recording that encodes an audio signal in a series of binary numbers (ones and zeros). Compact disc players, digital audio tape (DAT) decks, and digital signal processors all use PCM encoding.

Peak indicator: Usually a flashing LED on a tape recorder that indicates when transient signal levels have exceeded the recorder's ability to handle them without distortion; a supplement to recording-level meters.

peak-reading meter: A recording-level meter that rises rapidly and declines at a moderate speed so the user cartridge the levels of transient peak waveforms.

Phono: Abbreviation for "phonograph"; used to refer to the low-level signals produced by a phono cartridge and to the phono input where a turntable is connected to a preamplifier, integrated amplifier, or receiver. Phono inputs use RCA connectors, sometimes called phono plugs.

Piezo-electric (cartridge): A phono cartridge with a ceramic, crystal, or electret generating element that produces electricity when bent, twisted, or stressed. The cartridge's output, which can be fairly high, is proportionate to the amplitude of the stylus motion, rather than stylus velocity. See magnetic cartridge.

Piezo-electric speaker: A speaker principle used in some tweeters that employs a ceramic element which expands or bends when fed a signal voltage. This deflection generates sound.

Pivoted tonearm: The most common type of tonearm, it swivels on a fixed point so that the cartridge it holds can track the record groove from edge to center along a shallow are. See linear tracking tonearm.

PLL (phase-locked loop): A type of tuner circuit that improves reception of radio broadcasts by locking the received frequency to a synthesized reference frequency, which is usually generated by a quartz crystal.

P-mount: A standardized type of phono cartridge that plugs into a specific kind of tonearm; it requires no adjustment or calibration.

port: An opening in a bass-reflex speaker system that allows the sound wave from the back of a driver to reinforce the sound wave from the front.

power amplifier: A component that takes the audio signal from a preamplifier and makes it strong enough to drive speakers.

preamplifier: A component that switches and processes audio signals from source components. Typically, preamplifiers amplify only the low-level phono signals from turntables (more precisely, from phono cartridges), raising them to the same level as signals from other source components (called "line level") and applying the necessary RIAA equalization.

preset: On a tuner or receiver, a memory position where the frequency of a selected radio station can be entered for instant recall.

programming: Giving a component instructions to carry out at a later time. For instance, many compact disc players can be programmed to play selected tracks in any order.

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quantization: In a digital audio signal, the number of possible values available to represent various levels of amplitude. In a CD (compact disc) system, the resolution of the quantization is 16 bits, which means that each sample can have any value between zero and 65,535. Higher figures are better because they allow for more accuracy. See sampling frequency.

quartz-synthesis: See PLL.

random access: The ability to go directly to the beginning of a song, track, or program without having to scan the intervening material; the process is usually initiated using numbered buttons on a component's front panel or remote control.

RCA connector: The most common kind of connector for home audio systems, using small, one-pin phono plugs. The cables usually come in pairs, with the right channel marked in red and the left channel in black, gray, or white.

receiver: An audio component that performs three basic functions: receiving radio broadcasts, switching and processing audio signals, and amplifying the selected signal so it can drive speakers.

record: A 12-inch vinyl disc, also known as an LP or long-playing record, with intricate grooves that contain analog audio information. By vibrating in these grooves, the stylus of a phono cartridge converts mechanical information into a usable audio signal that can be amplified and sent to a pair of speakers. Seven-inch vinyl discs are called 45-rpm records, or singles.

recording-level meter: An indicator on a tape recorder that displays the signal levels being recorded onto tape from moment to moment; used to set proper recording levels.

RF (radio-frequency): The very high frequency signals used to broadcast radio programs.

RFI (radio-frequency interference): Noise created in audio systems by interference from strong, nearby radio broadcasts.

RIAA: The Recording Industry Association of America, which has set standards for the equalization used on phonograph records. Every record has reduced bass and boosted treble, and these characteristics must be compensated for on playback by the phono preamplifier.

ribbon speaker: A form of high-frequency driver using a light ribbon suspended in a magnetic field that generates sound when current is passed through it.

rms (root mean square): A common method of averaging power measurements.

rpm: Revolutions per minute.

rumble: A measurement of how much motor noise is transmitted through a turntable to the cartridge. Lower figures are better.

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Sampling The process of representing the amplitude of a signal at a particular point in time.

Sampling frequency (or rate): In digital audio, the number of times a signal is sampled each second. The standard sampling rate for the CD (compact disc) format is 44.1 kHz, which means each second of sound is encoded by 44,100 numbers for each channel. Higher sampling rates are better because they can record higher frequencies.

SAP (separate audio program): A separate mono channel that is broadcast along with the two stereo channels in the MTS system for stereo TV. The SAP channel can be used for various purposes, such as providing an alternative soundtrack in a language different from that used on the primary channels.

saturation: A condition that occurs when an audio tape becomes fully magnetized and an increase in signal input level does not produce a corresponding increase in recorded level. Saturation also can occur in the magnetic structure of the tape heads.

scan: A tuner feature used to move quickly from one broadcast station to another, stopping on each frequency for a few seconds so the user can sample it. On compact disc players, the scan feature is used to move around quickly within a track, much like fast forward on a tape deck.

Selectivity (sel): A specification that tells how well a tuner or receiver can differentiate between the selected broadcast channel and other stations using nearby frequencies. Adjacent channel selectivity (adj-ch sel) measures rejection of signals from stations broadcasting on either side of the selected station; alternate-channel selectivity (alt-ch sel) measures rejection of signals from stations two channels away from the desired one. Higher numbers are better for both of these specifications.

semiautomatic turntable: A kind that lifts the tonearm from the record automatically at the end of a side; the stylus must be set onto the record by hand, however.

sensitivity (sens): A measurement of speaker efficiency that tells how much sound is produced 1 meter away from the speaker with an input of2.83 volts (1 watt into 8 Ohms). Higher numbers are better.

Separation: The difference, measured in decibels (dB), between the left and right Channels of an audio Signal, indicating the amount of leakage between channels in a component. Higher figures are better.

Servo control: A technique that forces the speed or position of a moving device into conformity with a desired speed or position. The speed of a servo-controlled Turntable is established by a precision voltage or Frequency standard to which it is compared. Automatic adjustments are made to minimize differences and ensure the correct rpm.

signal: An electrical current that is modulated (changed) to represent information.

S/N (signal-to-noise ratio): Measured in Decibels (dB), the difference in level between the loudest possible Signal a component can produce and its residual Noise. Higher figures are better.

Source: The program signal that is being recorded or played back. Components provide program signals either by playing a recorded program (Turntables, Cassette decks, Compact Disc players, etc.) or receiving a broadcast program (Tuners and Receivers).

Specification (spec): A numerical measurement of a component's performance as provided by the manufacturer under laboratory conditions.

speaker (or Loudspeaker): A component that accepts audio Signals from a Receiver or Amplifier and converts them into sound waves. Also called a Driver.

Spherical stylus: A stylus whose shape is conical; typically used in cheaper Cartridges. The downward-facing point of the cone, which vibrates in the record groove, is rounded to a specified radius of curvature. See elliptical

SPL (sound-pressure level): A measurement of acoustic energy, usually encountered in the Sensitivity rating of a Speaker. See dB.

Stereo: The use of at least two separate Channels (signal paths) to create the illusion that music is being produced in the space between, and even beyond, a pair of Speakers.

Stylus: The needle-shaped material, usually diamond, at the end of the Cantilever of a Phono Cartridge; it vibrates in Record grooves, providing the cartridge with the energy needed to produce audio Signals.

Sub-Sonic: A speed/velocity less than that of sound in a designated medium. [Use Infrasonic if referring to frequencies below human hearing range.]

Sub-Woofer: A separate Speaker designed to reproduce only Bass frequencies. Subwoofer systems sometimes contain an Amplifier and a Crossover network.

Supertweeter: A Tweeter used to reproduce only extremely high frequencies; usually found in four- or five-way speaker systems.

Surround sound: See Dolby Surround.

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Tape Monitor: A switch on a tape recorder that allows the user to listen to a tape as it is being recorded to insure proper recording; also may allow external signal processors to be used.

THD (total harmonic distortion): The percentage of an audio signal that consists of harmonics, or multiples of the fundamental frequencies. These harmonics are introduced by an amplifier or other component in its handling of the original signal. Lower figures are better.

tonearm: The cylindrical rod on a turntable that supports the phono cartridge. See pivoted tonearm and linear-tracking tonearm.

tracking: The ability of a compact disc player or phono cartridge to follow the pattern recorded on a CD or vinyl record.

tracking error: In playing a record, the tonearm should hold the cartridge as perpendicular to the record's surface as possible. Tracking error is expressed as the number of degrees away from perpendicular.

tracking force: The pressure of a stylus on a record, measured in grams.

transport: The parts of a tape deck that move the tape, including the motor(s), hubs, capstan(s), pinchroller(s), and other mechanisms. In a compact disc player or turntable, the transport system rotates the CD or record.

transducer A device that converts one form of energy to another form, which include electrical, mechanical, acoustic, electromagnetic, chemical, optical, thermal energy.

treble: The high part of the audio frequency range; see bass and midrange.

tuner: A component that receives radio signals from an antenna and allows the user to select a specific station.

turntable: Also known as a phonograph or record player, a turntable rotates vinyl records; see cartridge and stylus.

tweeter: A driver in a speaker system that is designed to reproduce treble sounds (high frequencies).

two-way, three-way: Refers to the number of frequency bands a speaker system's output is divided into. A two-way system typically has a woofer and a tweeter, a three-way system adds a midrange speaker to that configuration. Systems up to five-way have been marketed.

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volume: Usually expressed in decibels (dB), the strength of a sound wave or audio signal.

W/ch (watts per channel): A specification that indicates how much power an amplifier or receiver will deliver to each of a pair of speakers.

W&F (wow-and-flutter): A combined specification indicating the speed accuracy of mechanical components such as turntables and cassette decks. Lower figures are better. See wow and flutter.

woofer: A driver in a speaker system designed to reproduce the low, or bass, part of the audio frequency spectrum.

Wow: A measurement of slow speed variations; usually combined with flutter, a measurement of fast speed variations. Lower figures are better.

Zobel network: A crossover network that is designed to compensate for the non-linearity of speakers as the actual impedance varies with frequency.

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AC--alternating current

A/D--analog to digital

AFC--automatic frequency control

alt-ch--alternate channel


CD--compact disc

CIRC--cross interleave Reed-Solomon code

CrO2--chromium dioxide

D/A--digital to analog

DAT--digital audio tape


dBf--decibel femtowatt

DC--direct current

EE--extra efficiency

EFM--eight-to-fourteen modulation

EIA--Electronic Industries Association

EIAJ--Electronic Industries Association of Japan




FET--field-effect transistor

FR--frequency response


HD--harmonic distortion

H.D-- High Definition (relating to Video)

HX--headroom extension

Hz-hertz (cycles per second)

IC--integrated circuit

IEC--International Electrotechnical Commission

IEEE--Institute of Electrical Electronic Engineers

IF--intermediate frequency

IHFF-Institute of High Fidelity

IM--intermodulation (distortion)


IPS--inches per second (relating to audio tape speed)

I.P.S-- In Plane Switching (relating to video panel type)

k--one thousand

kHz--kiloHertz (one thousand cycles per second)

LCD--Liquid-Crystal Display

LED--Light-Emitting diode

OLED--Organic Light-Emitting Diode


LSI--large-scale integrated (circuit)

m--meter (as in SPL/W/m)

m--milli (one thousandth, as in msec)

Mb/sec--megabits per second

MC--moving coil

MM-moving magnet

MNOS-metallic nitrogen-oxide semiconductor

MOL--maximum output level

MOSFET--metal-oxide semiconductor field-effect transistor






µ--micro (one millionth)

MSB--most significant bit

NAB--National Association of Broadcasters

nWb--nano Weber

NR--noise reduction

PCM--pulse-code modulation


PLL--phase-locked loop

P-P--peak-to-peak, push pull

RF--radio frequency

RIAA--Recording Industry Association of America

rms--root mean square(0.717 of peak)

RPM--revolutions per minute




SMPTE--Society of Motion Picture and Television Engi-


S/N--signal-to-noise ratio (measured in dB)

SPL--sound-pressure level

THD--total harmonic distor-


TIM--transient intermodulation


VU--volume unit


W&F--wow and flutter


wrms--weighted root mean square


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