T.H.E. Glossary

The Definitive List of 329+ High End Audio Definitions


AC line conditioner- device that filters noise from the AC powerline and isolates equipment from voltage spikes and surges.

Acoustic space –1) A large performance space or recording venue. 2) All the spatial and reverberant characteristics of the performing hall or venue are captured and preserved in the master recording.

“Ah” (rhymes with “Rah”) – A vowel coloration caused by a frequency-response peak centered around 1000Hz.

Airy – Describes the space and openness of the product usually associated with open back headphones and live sounding music.

Airy – Reproduced audio in which the treble sounds light, delicate, open, and seemingly unrestricted in upper frequency extension. A quality of reproducing systems having very smooth and very extended HF response.

Alternating current (AC)- flow of electrons in a conductor that reverses its polarity many times per second. The AC mains in oscillate at either 50 or 60 Hz.

Ambience – (pronounced “ambee-ints”) The sound of a performance hall or recording venue. Typically associated with the amount of early reflections and reverberation time.

American wire gauge (AWG)- standardized method of specifying wire thickness. The lower the AWG number, the thicker the wire.

Ampere- A unit of electrical current.

Analog bypass- input on a digital controller that passes along analog input signals to its analog outputs without first converting them from analog to digital and from digital back to analog.

Attack – 1) The initial sound produced when an instrument is bowed, blown, struck, or plucked.

Attack transient – The initial energy pulse of a percussive sound, such as from a piano string, triangle, or drum head.

Audio band- the range of human hearing; generally considered to be 20 Hz to 20 kHz.

A/V- abbreviation of audio/video. Identifies as a component or system that processes video as well as audio signals

A/V input- and input on an A/V receiver or A/V preamplifier that includes both audio and video jacks.

A/V loop- an A/V input and A/V output pairing found on all A/V receiver and A/V preamplifiers. Used to connect a component that record as well as plays audio and video signals

A/V preamplifier- a component, a.k.a. an A/V controller, that lets you control the playback volume and select which source you want to watch. A/V preamplifiers also perform surround decoding.

A/V preamplifier/tuner- an A/V preamplifier that includes, in the same housing, and AM and FM tuner for receiving radio broadcast.

AV receiver- the central component of a home-theater system; receive signals from source component, is used to select which signal you watch and listen to you and to control the playback volume, perform surround decoding, receives radio broadcast, and amplifies the signals to drive a home theater loudspeaker. Also called surround receiver.

“Aw” – (rhymes with “paw”) A vowel coloration caused by a frequency-response peak centered around 450Hz. An “aw” coloration tends to emphasize and glamorize the sound of large brass instruments (trombone, tuba).


Balance – Equality of signal level between the left and right stereo channels, which centers the soundstage and allows mono program material to image at the center. Also called channel balance.

Balanced connection- a method of connecting audio component with three conductors and a single cable. One connector carries the audio signal, a second conductor carries that audio signal with inverted polarity, and the third conductor is the ground.

Banana jack- a small, tubular connector found on some loudspeakers and power amplifiers for connecting speaker cables terminated with banana plugs.

Banana plug- a common speaker-cable termination that fits into a banana jack.

Bandwidth- the range of frequencies that your device can process or pass. In reference to an electrical or acoustic device, bandwidth is the range of frequencies between the -3dB points.

Bass – This is the lower end frequency of the human hearing. The range of frequencies below about 150 Hz, characterized by low pitch.

Bi-amp- using two power amplifiers to drive one loudspeaker. One amplifier typically drives the woofer, the second drives the midrange and tweeter.

Binaural – Literally hearing with “two ears,” refers to a recording/playback system. Recordings are either recorded using a human head with two in ear microphones or a binaural head system and played back using headphones or crosstalk cancelling speakers

Binding post- a connection on power amplifiers and loudspeakers for attaching loudspeaker cables.

Bipolar transistor- the type of transistor is most commonly used in audio electronics. The term, which means two poles, comes from the fact that current flows through two types of semiconductor material, P and N. Bipolar transistors are either in NPN or PNP types, which refers to the polarity of their operating voltages.

Bi-wire- technique of running two cables to each loudspeaker. One cable is connected to the loudspeaker’s woofer input terminals, one to the tweeter’s input terminals. Bi-wiring is possible only with loudspeakers with two pairs of input terminals.

Break-in- initial period of use of a new audio component, during which time the component’s sound might improve.

Breathing – From a dynamic noise-reduction system: audible changes in the level of background hiss in accordance with changes in signal volume. See “pumping.”

Bridge rectifier- and arrangement of four diodes that converts the alternating current (AC) from the powerline into pulsating direct current (DC).

Bridging– method of connecting a stereo amplifier to a loudspeaker that converts a 2-channel amplifier into a 1-channel power amplifier. One amplifier channel amplifies the positive path of the waveform, other channel amplifies the negative. The loudspeaker is connected as a “bridge” between the two amplifier channels.

Bright/Brightness – usually displayed in the upper frequencies or upper mids. Brightness is a feature enjoyed by many but walks a thin line to becoming unpleasant due to a potential of treble peaking.

Buffer- electronic circuit that isolates one component or circuit stage from another. A preamplifier is a buffer because they act as an intermediary between source component and a power amplifier; the preamplifier’s buffering function relieves this source components of the burden of driving a power amplifier.

Burn in- process of improving and audio component’s sound quality by leaving it powered on, or by running audio signals through it.

Buzz – A low-frequency sound usually at 60 Hz or multiples having a spiky or fuzzy character.

Bypass test – Directly comparing the output signal from a device with the input signal being fed to it, by putting the device into and then out of the signal path and observing the difference.


Capacitive reactance- property of capacitance blocks low frequencies that passes along high frequencies. Capacitive reactance makes a capacitor to behave as a frequency-dependent resistor. Because of the capacitive reactance, a capacitor connected to a tweeter Allows treble to pass but blocks bass.

Capacitor- electronic component that stores a charge of electrons. Reservoir capacitors are used in power amplifiers to store energy; filter capacitors filter traces of AC from DC power supplies; coupling capacitors connect one amplifier stage to another by blocking DC and allowing the AC audio signal to pass.

Channel balance- the relative levels or volumes of the channels in an audio system or individual component.

Channel separation- a measure of how well sound in one channel are isolated from sounds in another channel.

Chassis- the framework on which an audio component is built. The case typically fits over the chassis.

Class A- mode of amplifier operation in which a transistor or tube amplifies the entire audio signal.

Class AB- Mode of amplifier operation in which the output stage operates in Class A at low output power, then switches to Class B at higher output power.

Class B- mode of amplifier operation in which one tube or transistor amplifies the positive half of an audio signal, and the second tube or transistor amplifies the negative half.

Class D- mode of amplifier operation in which the output transistors rapidly turn fully on and fully off. The analog waveform is encoded in the width of the resulting pulses. See also switching amplifiers.

Clean – Free from audible distortion.

Click – A small, sharp impulse that sounds like the word “click.”

Clipping- an amplifier that is asked to deliver more power than it is capable of will flatten the top and bottoms of the audio waveform, making the peaks appeared to be clipped off when the waveform is viewed on an oscilloscope. Clipping introduces a large amount of distortion, audible as a crunching sound on musically peaks.

Coloration – An audible “sonic signature” with which a reproducing system imbues all signals passing through it. Ideally, a properly designed system will induce no coloration.

Common-mode rejection- when a balance signal is input to a differential amplifier, only the difference between the two phases of the balance signal is amplified. Any noise common to both phases (common-mode noise) is rejected by the differential amplifier.

Comb filtering – A hollow coloration that, once recognized, is unmistakable. Caused by a regularly spaced series of frequency-response peaks and dips, most often due to interference between two identical signals spaced in time. If that time difference is continually changed, the comb-filter peaks and dips move accordingly, giving rise to the familiar “phasing,” “flanging,” or “jet plane” effect used in modern rock music.

Consonant – Agreeable to the ear; pleasant-sounding. Compare “dissonant.”

Controller- another term for an A/V preamplifier

Crackle – Intermittent medium-sized clicks. The usual background noise from much-played vinyl discs.

Crossover distortion- see zero-crossing distortion

Cross talk- see channel separation

Current- the flow of electrons in a conductor. For example, a power amplifier “pushes” electrical currents through speaker cables and the speaker’s voice coils to make the coils move back-and-forth.


Damp- to decrease the amplitude and duration of vibration.

Damping – The amount of control an amplifier seems to impose on a woofer. Underdamping causes loose, heavy bass; overdamping yields very tight but lean bass.

Damping factor- a number that expresses a power amplifier’s ability to control woofer motion. Related to the amplifier’s output impedance.

dBSPL- (decibels reference to sound pressure level) A measurement, in decibels, of loudness sound pressure level reference to the threshold of hearing (0dBSPL).

DBW (decibel watt)- A measurement of amplifier power in decibels (dB) referenced to one watt (W) of output power.

Decay – How a sound/note/resonance fades away ie the note decay was lengthy.

Decay – The reverberant fadeout of a musical sound after it has ceased. Compare “attack.”

Dedicated AC line- an AC circuit that powers only your audio equipment.

Deep bass – Frequencies below 40Hz.

Depth – The illusion of acoustical distance receding behind the loudspeaker plane, giving the impression of listening through the loudspeakers into the original performing space, rather than to them. See “layering,” “transparency.” Compare “flat.”

Depth – How far away the instruments spacing is from back to front.

Detail – The attention to a full reproduction with all sound/notes being audible and present.

Dielectric- insulating material inside a capacitor or around a cable

Differential amplifier- electronics circuit that amplifies only the difference between the two phases of a balanced signal.

Diffuse – Reproduction which is severely deficient in detail and imaging specificity; confused, muddled.

Digital amplifier- Amplifier that accepts a pulse-code-modulated (PCM) audio signal and converts it to a pulse-width-module (PWM) signal that turns the amplifier’s output transistors on and off. Not to be confused with a Class D amplifier, which has an analog signal path and a switching output stage.

Digital preamplifier- audio component that performs source selection, volume control, and other functions in the digital domain.

Digital signal processing (DSP)- manipulation of audio or video signals by performing mathematical functions on the digitally encoded signal

Dip – A narrow area of depression within an otherwise flat frequency-response curve. Compare “dished,” “humped.”

Direct coupled- electronic circuit in which no coupling capacitors are in the signal path

Direct current (DC)- flow of electrons that remain steady rather than fluctuating. Compare with alternating current (AC).

Direct sound – A sound reaching the ears in a straight line from its source. The direct sounds are always the first sounds heard. The “critical distance” from a soundsource is when the spl of the direct sound is equal to that of the reverberant field. See “far field,” “near field,” “precedence effect.” Compare “reflected sound,” “reverberation.”

Discrete- separate. A discrete circuit uses separate transistors instead of an integrated circuit. A discrete digital surround-sound format contains 5.1 channels of audio information that are completely separate from each other; this differs from a matrixed surround format such as Dolby Surround, in which the channels are mixed together for transmission or storage.

Dissonant – Unpleasant to the ear; ugly-sounding. Dissonance is an imperfection only when the music is not supposed to sound dissonant. Compare “consonant.”

Distortion – 1) Any unintentional or undesirable change in an audio signal. 2) An overlay of spurious roughness, fuzziness, harshness, or stridency in reproduced sound.

Double (or dual) mono – Reproduction of a monophonic signal through both channels/speakers of a stereo system, as when a preamplifier’s mode switch is set to A+B (L+R). Compare “single mono.”

Dry – an acoustical space: deficient in reverberation or having a very short reverberation time.

DSP (digital signal processing) room correction- technique of removing room-induced frequency-response peaks and dips with digital signal processing.

Dull – Lifeless, muffled, veiled. The audible effect of HF rolloff setting in at around 5kHz.

Dynamic – Giving an impression of wide dynamic range; punchy. This is related to system speed as well as to volume contrast.

Dynamic range – 1) Pertaining to a signal: the ratio between the loudest and the quietest passages. 2) Pertaining to a component: the ratio between its no-signal noise and the loudest peak it will pass without distortion.


Echo – In an acoustical space: the repetition of a sound due to reflection of the original sound from a room boundary. See “hand-clap test,” “fluttery,” “slap.”

Echoey, echoic – Pertaining to an acoustical space having excessive reverberation. Can also (rarely) be characteristic of a loudspeaker with excessive mid-frequency mechanical resonances.

“Ee” – (rhymes with “we”) A vowel coloration caused by a frequency-response peak centered around 3.5kHz.

“Eh” – (as in “bed”) A vowel coloration caused by a frequency-response peak centered around 2kHz.

Electromagnetic interference (EMI)- disturbance caused by the radiation of electromagnetic waves.

Element – One of the constituent parts of a sonic characteristic. Bass, midrange, and treble are elements of frequency response. Depth and breadth are elements of soundstaging.

Equalization- the modification of the system’s total balance by employing an equalizer.

Equalizer- A circuit that changes the tonal balance of an audio program. Bass and treble controls are types of equalizers.

Euphonic – Pleasing to the ear. In audio, “euphonic” has a connotation of exaggerated richness rather than literal accuracy.

Extension – The usable limits of a component’s frequency range.

Extreme highs – The range of audible frequencies above 10kHz.


Far field – Pertains to that range of listening distances in which the predominant sounds reaching the ears are reflections from room boundaries.

Fast Fourier Transform (FFT)- Mathematical technique that converts information from the time domain to the frequency domain.

Feedback- In amplifier circuits, returning part of the output signal to the amplifier’s input. Feedback reduces distortion and makes the circuit more linear. See also acoustic feedback.

Field Effect Transistor (FET)- A type of transistor that uses an electric field to control current flow through the transistor. Because of their very high input impedance and very low noise, FET’s are often used in the input stages of preamplifiers and phono stages.

Filter- Electronic circuit that selectively removes or reduces the amplitude of certain frequencies.

Filter capacitor- Large capacitor used in power supplies to filter traces of 60 Hz AC from the DC supply.

Flanging – See “comb filtering.”

Flat – 1) Having a subjectively uniform frequency response, free from humps and dips. 2) Deficient in or lacking in soundstage depth, resulting in the impression that all reproduced sound sources are the same distance from the listener.

Frequency range – A range of frequencies stated without level limits: ie, “The upper bass covers the frequency range 80-160Hz.”

Frequency- number of repetitions of a cycle. Measured in hertz (Hz), or cycles, per second. An audio signal with a frequency of 1000Hz (1kHz) undergoes 1000 cycles of a sinewave per second.

Frequency (or amplitude) response – 1) A range of frequencies stated with level limits: ie, “The woofer’s response was 20-160Hz ±3dB.” 2) The uniformity with which a system or individual component sounds as if it reproduces the range of audible frequencies. Equal input levels at all frequencies should be reproduced by a system with subjectively equal output.

Frequency response- a graphical representation of an audio device’s relative amplitude as a function of frequency.


Gain- Number expressing the amount of amplification provided by the amplifier. An amplifier that can convert a signal with an amplitude of 0.1V to 1V is said to have a gain of 10.

Ground- a reference point from which all voltages are measure; typically, the potential of the earth.

Ground loop- in AC power, unwanted current flow through the ground caused by multiple ground paths of varying resistances.


Hand-clap test – The use of hand claps to assess the reverberant properties of a room.

Harmonic distortion- The production of spurious frequencies at multiples of the original frequency. A circuit amplifying a 1kHz sinewave will create frequencies at 2kHz (second harmonic), 3 kHz (third harmonic), and so forth.

Heatsink- Large metal device that draws heat away from the interior of an electronic device to dissipate it in air. The fins protruding from the sides of power amplifiers are heatsinks.

Hertz (Hz)- the unit of frequency; the number of cycles per second; kilohertz (kHz) is thousands of cycles per second.

HF – High frequency(ies).

High-end – Pertains a) to sound that closely approaches the real thing, b) to audio equipment whose performance is near the top of the quality scale, and often the price scale.

High-end audio – The pursuit of and business of realistic sound reproduction.

High fidelity – 1) A kind of sound-reproducing system whose realism of reproduction is judged to be better than average. Stereo reproduction can be high-fidelity or otherwise. 2) The pursuit of perfection in sound reproduction, as a hobby or a religion.

High-frequency range – 1) The audio range above 1300Hz. 2) The usable upper limit of that range. See “extension.”

High-pass filter- a circuit that allows high frequencies to pass but blocks low frequencies. Also called a “low-cut filter.” High-pass filters are often found in A/V receivers and A/V preamplifiers to keep bass out of the front speakers when a subwoofer is used. Many powered subwoofers also include high-pass filters.

Highs – The upper frequencies/ higher notes.

Horn sound – An “aw” coloration characteristic of many loudspeakers that have a horn-loaded midrange.

Hum – A continuous 60Hz or 120Hz noise, caused by leakage of the household AC supply or its second harmonic into the signal path.

Hybrid- AN audio component that combines more than one technology; e.g., an amplifier that contains tubes and transistors, a loudspeaker that contains tubes and transistors, a loudspeaker that contains dynamic and ribbon drivers, etc.


IC (Integrated circuit)- A semiconductor that incorporates many parts, such as transistors and resistors, in one monolithic package, aka a chip.

“Ih” – (as in “bit”) A vowel coloration caused by a frequency-response peak centered around 3.5kHz.

Image – See “phantom image.”

Imaging – The measure of a system’s ability to float stable and specific phantom images, reproducing the original sizes and locations of the instruments across the soundstage. See “stereo imaging.”

Impact – A quality of concussive force, as from a deep, strong bass attack, which produces a brief sensation of visceral pressure.

Impedance– resistance to the flow of AC electrical current. An impedance is a combination of resistance, inductive reactance, and capacitive reactance, measured in ohms.

Impulse – An abrupt, extremely brief burst of signal energy; a transient.

Impulse noise – Transient noise, such as surface-noise ticks and pops.

Inaudible – A sonic imperfection which is either too subtle to be consciously perceived or is actually nonexistent. Compare “subliminal.”

Inductive reactance- the property of an inductor in which the inductor’s opposition to current flow increases as frequency increases.

Inductor- electronic component that increases its opposition to current flow as frequency increases. Many loudspeaker crossovers use a large on the woofer to filter out high frequencies.

Infrasonic – Below the range of audible frequencies. Although inaudible, the infrasonic range from 15-20Hz can be felt if strongly reproduced. Compare “subsonic.”

In phase- stereo speaker connection in which each speaker’s positive (red) terminal is connected to the amplifier’s positive terminal, and each speaker’s negative (black) terminal is connected to the amplifier’s negative terminal. When fed a monophonic signal, both speakers’ cones move forward and backward in synchrony. Contrast with out-of-phase connection in which one speaker’s cone moves forward while the second speaker’s cone moves backward. Speakers connected out of phase have diffuse imaging and reduced bass output.

Input Impedance – the resistance to current flow presented by a circuit or component to the circuit component driving it. Impedance is a combination of resistance, Capacitive reactance, and inductive reactance

Input overload- a condition in which a component (typically, a preamplifier) produces severe distortion because the signal driving it is too high in level. For example, connecting a high-output moving-magnet cartridge to a preamplifier’s moving-coil input could overload the preamplifier’s input and produce audible distortion.

Integrated amplifier- Audio product combining a pre-amplifier and power amplifier on a single chassis in a single case or housing

Intermodulation distortion (IMD)- distortion introduced by amplifier circuits that comprises the sum and difference of the input signal. For example, an amplifier driven with a mix of 1 kHz and 5 kHz frequencies generates intermodulation distortion products at 6 kHz (the sum of 1 kHz and 5 kHz) and at 4 kHz (the difference between 1 kHz and 5 kHz). These IMD products then intermodulate with each other to create a nearly infinite series of distortion products.

Isolation transformer- A transformer whose only function is to transfer signals or power from one point to another without a physical connection. It does this through electromagnetic induction, in which two coils of wire are positioned next to each other. Current flow through the one coil induces a current flow in the second coil.


JFET (junction field effect transistor)- type of transistor often used in preamplifier input stages that differs in internal structure and operation from the more common bipolar transistor. JFET‘s are lower in noise and are driven by voltage rather than current, more closely mimicking the operation of vacuum tubes.


KiloHertz- 1000 Hertz, abbreviated kHz


LF – Low frequency(ies).

Lifeless – Sound that is dull, unfocused, unconvincing, and uninvolving.

Light Lean and tipped-up – The audible effect of a frequency response which is tilted counterclockwise. Compare “dark.”

Linear- and output that varies in precisely direct proportion to the input. Can also describe a traditional (non-switching) power supply or amplifier.

Line level- and audio signal with an amplitude of approximately 1 V to 2 V. Audio components into face at line level through interconnects. Compare with speaker level, the much more powerful signals that drive loudspeakers.

Listening distance – The distance from the listener to the loudspeakers. See “critical distance,” “far field,” “near field.”

Listening fatigue – A psychoacoustic phenomenon from prolonged listening to sound whose distortion content is too low to be audible as such but is high enough to be perceived subliminally. The physical and psychological discomfort can induce headaches and nervous tension.

Live – 1) Describes an acoustical space having a great deal of reverberation. 2) Pertains to the sound of actual instruments or voices in performance, as opposed to the sound of their reproduction.

Localization – In stereo reproduction, the placement of phantom images in specific lateral positions across the soundstage. Also, the specificity of those images.

Low bass – The range from 20-40Hz.

Low-cut level- A circuit that removes bass frequencies from an audio signal. Also called a high-pass filter.

Lower highs – The range of frequencies from 1.3-2.6kHz.

Lower middles, lower midrange – The range of frequencies from 160-320Hz.

Low frequency – Any frequency lower than 160Hz.

Low-level detail – The subtlest elements of musical sound, which include the delicate details of instrumental sounds and the final tail of reverberation decay. See “delicacy.”


MF – Middle frequency(ies), the all-important midrange.

Midbass – The range of frequencies from 40-80Hz.

Middle highs – The range of frequencies from 2.6-5kHz.

Middles, midrange – The range of frequencies from 160-1300Hz.

Mids/Midrange – The middle frequencies (usually the main body of vocals and acoustic guitars amongst others ((see instrument frequency chart))

Modulation noise – A hiss or other extraneous noise which “rides on” the main signal, varying in loudness according to the strength of that signal.

Monaural – Literally “hearing with one ear.” Often used incorrectly in place of monophonic (as in Glenn D. White’s otherwise excellent Audio Dictionary, 1991, second edition, University of Washington Press.—JA). Compare “binaural.”

Monophonic, mono – A system or recording with one channel or speaker. See “monaural,” “single mono,” “dual mono.”

MOSFET (metal-oxide semiconductor field effect transistor)- A transistor that is turned on (biased) by voltage rather than by current. Compared with bipolar transistor.

Muffled – Very dull-sounding; having no apparent high frequencies at all. The result of HF rolloff above about 2kHz.

Multichannel power amplifier- A power amplifier with more than two channels; usually, five or seven.

Multichannel preamplifier- A pre-amplifier with more than two channels; usually, six or eight.


Nasal – Reproduced sound having the quality of a person speaking with his/her nose blocked. Like the vowel “eh” coloration. In a loudspeaker, often due to a measured peak in the upper midrange followed by a complementary dip.

Natural – Sounds as it should, real and true to life.

Naturalness – Realism.

Near field – Pertains to that range of listening distances in which the sounds reaching the ears are predominantly direct. See “far field,” “critical distance.”

Neutral – Free from coloration.

New old stock (NOS)- vacuum tubes manufacture long ago – perhaps decades ago – that have never been used.

Noise – Any spurious background sounds, usually of a random or indeterminate pitch: hiss, crackles, ticks, pops, whooshes.

Noticeable – In aural perception, any sonic quality which is clearly audible to most people.


“Oh” (as in “toe”) – A vowel coloration caused by a broad frequency-response peak centered around 250Hz.

Ohm- The unit of resistance to electrical current flow.

Ohm’s law- expresses the relationship between voltage, current, and resistance and electrical currents. If you know two of the values (e.g., current and resistance), you can calculate the third value by using Ohm’s law. Named for its discoverer, Georg Ohm.

“Oo” (as in “gloom”) – A vowel coloration caused by a broad frequency-response peak centered around 120Hz.

Op-amp (operational amplifier)- an integrated circuit that combines several transistors and supporting circuitry into a ready-made amplifier. Compare with a discrete amplifier with individual transistors.

Out of phase- stereo speaker connection in which one speaker is connected to the amplifier with the positive (red) and negative (black) wires reversed. When fed a monophonic signal, one speaker’s cones move backward. Speakers connected out of phase have diffuse imaging and reduced bass. Contrast with in-phase connection, in which both speakers’ cones move forward and backward in synchrony.

Out-of-phase – In a two-channel system, one channel being in opposite polarity to the second, most commonly due to having one speaker hooked up with the red (positive) lead to the red (positive) terminal, the other with the red lead to the black (negative terminal). As well as a “phasey” sound, the result will be a reduction in low frequencies. See “phasey.”

Output impedance- technically, the change in a component’s output voltage in response to a change in load impedance. Practically, a component with a high output impedance can deliver less current to a load than a component with a low output impedance. Low output impedance is preferable.

Output stage- The last amplifier in an audio component. A DAC’s output stage is an amplifier that drives the preamplifier. The power amplifier’s output stage delivers current to the loudspeakers.

Output transformer- transformer in tubed amplifiers that couples the output stage to the loudspeaker. Output transformers are required in tuned amplifiers to change the amplifier’s high output impedance to a lower value that can better drive loudspeakers. The output transformer also blocks DC from appearing at the amplifier’s output terminals.

Overdamped – Pertaining to the audible effects of excessive woofer damping.


Passband- range of frequencies allowed through by a filter

Passive level control- Device that adjusts the volume of an audio system without using amplifiers or other active electronic components, such as tubes or transistor.

Peak- A short-term, high-level audio signal. Also: an excess of energy over a narrow frequency band (compare with dip).

Pentode- vacuum tube with five elements: the cathode, plate, screen grid, control grid, and suppressor grid. More efficient than the simpler triode vacuum tube.

Perceptible – At or above the threshold of audibility of a trained listener.

Period- The time it takes to complete one cycle in a sine wave.

Phantom image – The re-creation by a stereo system of an apparent sound source at a location other than that of either loudspeaker.

Phase- in a periodic wave, the fraction of a cycle that has elapsed, measured in degrees, with 360° representing one cycle. Describes the time relationship between two signals. For example, two sine waves, the second of which is delayed half a cycle relative to the first, are 180° out of phase.

Phase angle- A measurement of how interactive or capacitive a loudspeaker’s impedance is.

Phasey – A quality of reproduced sound which creates a sensation of pressure in the ears, unrelated to the intensity of the sound. Phasiness is experienced by many people when listening to two loudspeakers which are connected out of phase with each other.

Phasing – See “comb filtering.”

Pitch resolution – The clarity with which the pitch of (generally) bass notes is perceived. Poor pitch resolution makes all notes sound similar; good pitch resolution gives an impression that you “can almost count the cycles.”

Pop – A midrange pulse characterized by a very sharp attack followed by a short “o” or “aw” vowel sound. Usually the result of a severe LP blemish.

Power amplifier- and audio component that boosts a line-level signal to a signal powerful enough to drive loudspeakers.

Power bandwidth- The range of frequencies over which an amplifier can deliver its rated power output.

Power handling- how much amplifier power, measured in watts, a speaker can accept before it is damaged.

Power output- The power amplifier’s ability, measured in watts, to deliver electrical voltage and current to a speaker.

Power range – The frequency range about 200-500Hz that affects the reproduction of the power instruments of an orchestra—the brass instruments.

Power supply- circuitry, found in every audio component, that converts 60 Hz alternating current (AC) from the wall outlet to direct current (DC) to drive the audio circuitry.

Power transformer- Device in a power supply that reduces the incoming voltage from 120 V to the lower voltage.

Preamplifier- component that receives signals from source components, select the source for listening, controls the volume, and drives the power amplifier; literally, “before the amplifier.”

Preamplifier-processor- audio/video component that combines the pre-amplifier and surround-sound decoder on a single chassis. Can be thought of as an A/V receiver without power amplification or a tuner.

Precedence effect – The tendency for the ears to identify the source of a sound as being in the direction from which it is first heard. See “direct sound.”

Presence – A quality of realism and aliveness.

Presence range – The lower-treble part of the audio spectrum, approximately 1-3kHz, which contributes to presence in reproduced sound.

Pulse width modulation (PWM)- a digital representation of an audio signal in which the signal’s amplitude information is contained in the widths of a single-bit pulse.

Pumping – 1) The exaggeration of abrupt signal-amplitude changes, often due to the malfunctioning of a companding (compressing/expanding) noise-reduction system. 2) Audible fluctuations of background noise in the playback phase of compansion. 3) Large, spurious subsonic motions of a woofer cone, usually due to analog-disc warps or marginal LF stability in the power amplifier.

Push-pull amplifier- Power-amplifier topology in which a pair of opposing output devices, such as transistors, is a range so that one “pushes” current through the load and the other “pulls” current through the low. Contrast with single-ended amplifier topology.


Qualifier – An adjective which the listener attaches to an observed sonic imperfection (such as “peaky” or “muddy”) in order to convey a sense of its magnitude. “Subtle” and “conspicuous” are qualifying adjectives. See “audibility.”

Quality – The degree to which the reproduction of sound is judged to approach the goal of perfection.


Radio frequency (RF) noise- most often refers to spurious noise with energy in the radio-frequency band of several hundred kilohertz to tens of megahertz.

Rail- The power-supply voltage that supplies a component’s audio circuits.

Rail-fuse- fuse sometimes found on the back of a power amplifier, wired in series with the power-supply rail. The rail fuse will blow when excessive current is drawn by the amplifier’s stage.

RCA jack- a connector found on audio and video products. Analog and digital signals transmitted via RCA jacks include line-level audio and S/PDIF digital.

Reaction – A counterforce imparted to a speaker enclosure in response to the air resistance to the motion of a moving diaphragm or cone. On a thick carpet, a reacting enclosure will rock slightly back and forth, impairing LF quality and overall detail. See “spike.”

Rectifier- Device that converts AC current into DC current. Found in all power supplies.

Rectify- to convert AC current into DC current

Reflected sound – A sound which reaches the ears after being reflected from at least one boundary surface. See “critical distance,” “far field,” “near field,” “precedence effect.” Compare “direct sound.”

Resolution – See “definition.”

Reverberation – A diminishing series of echoes spaced sufficiently closely in time that they merge into a smooth decay.

Rhythm – See “timing.”

RIAA- Recording Industry Association of America

RIAA accuracy- flatness of the RIAA phono-equalization circuit in a phono preamplifier

RIAA equalization- A treble boost and bass cut applied to the audio signal when a record treble is cut; a reciprocal treble cut and bass boost on playback restores flat response. RIAA equalization makes it possible to increase the playing time of an LP side (bass takes up the most space in the record groove) and decrease noise (the treble cut on playback also reduces record-surface noise).

Rolloff – (also rollout) A frequency response which falls gradually above or below a certain frequency limit. By comparison, the term cutoff (often abbreviated to “cut,” as in “bass cut”) implies an abrupt loss of level above or below the frequency limit.

Rumble – An extraneous low-frequency noise, often of indeterminate pitch, caused by physical vibration of a turntable or of the room in which a recording was made.


Scrape flutter – Roughness and veiling of analog tape sound due to discontinuous movement of the tape across the head (“violining”).

Secondary windings- coils of wire in a transformer there aren’t physically connected to the AC line, but that supply voltage and current to the power supply through electromagnetic induction. Power transformers often have multiple secondary windings, to increase the isolation of each of a component’s multiple power supplies.

Servo- and electrical or mechanical system that controls the speed or position of a moving device by forcing it to conform to a desired speed or position. In a servo-controlled turntable, the platter’s rotational speed is compared with a reference frequency, and a correction signal is applied to the drive motor to keep the two frequencies identical. In an electrical circuit such as a DC servo, a correction signal continuously adjusts the amplifier circuit so that no DC appears at the output.

Sibilance – A coloration that resembles or exaggerates the vocal s-sound.

Sibilant – The high unpleasant peaks that are usually unpleasant to the ear if to prevalent.

Signal/ noise ratio- numerical value expressing in decibels the difference in level between an audio component’s noise floor and a reference signal level.

Single-ended amplifier- amplifier in which both half-cycles of the audio waveform are amplified by the output tubes and transistors. Compare with push-pull amplifier.

Single-mono – Sound reproduction through a single loudspeaker system. Compare “dual mono.”

Six-channel input- A pre-amplifier input comprising six discrete jacks that will accept the six discrete analog outputs from a multichannel disc player.

Size – See “width.”

Slap – In an acoustical space, a repeated echo recurring at a rate of about 3 per second, common to moderate-sized, bare-walled acoustical spaces. See “hand-clap test.” Compare “fluttery,” “plastery.”

Slew rate- The speed at which an amplifier can produce an output voltage in response to an input signal. Typically measured in volts per microsecond.

Solid-state sound – That combination of sonic attributes common to most solid-state amplifying devices: deep, tight bass, a slightly withdrawn brightness range, and crisply detailed highs.

Sonic detail – See “detail.”

Sound-pressure level (SPL)- A measure of loudness expressed in decibels (dB).

Soundstage – Described in 3D terms (height width and depth)

Soundstaging, soundstage presentation – The accuracy with which a reproducing system conveys audible information about the size, shape, and acoustical characteristics of the original recording space and the placement of the performers within it.

Soundstage shift – Apparent lateral movement of the soundstage when listening from either side of the sweet spot.

Source switching- function performed via a pre-amplifier or integrated amplifier, in which the user selects which source and components signals are fed to the speakers.

Spade lug- A speaker termination with a flat area that fits around a binding post

Spatiality – The quality of spaciousness.

Speed – The apparent rapidity with which a reproducing system responds to steep wavefronts and overall musical pace. See “fast,” “slow.”

Spike – 1) The “tick” sound of a pulse. 2) A sharp-tipped, conical supporting foot which allows the weight of a loudspeaker to be passed through carpeting to rest firmly on the underlying floor. Used to minimize speaker-enclosure reaction.

Spread – See “stereo spread.”

State-of-the-art – Pertains to equipment whose performance is as good as the technology allows. The best sound equipment money can buy.

Step-up transformer- Transformer with a higher output voltage than the voltage input to it. Sometimes used between a moving-coil cartridge and a moving-magnet phono input.

Stereo imaging – The production of stable, specific phantom images of correct localization and width. See “soundstaging,” “vagueness,” “wander.”

Stereophile – 1) The original magazine of subjective reviewing. 2) An audiophile who owns a stereo system.

Stereophonic – A two-channel recording or reproducing system. Compare “binaural,” “monophonic.” See “dual mono,” “single mono.”

Stereo spread – The apparent width of the soundstage and the placement of phantom images within it. Generally, a group of instruments or voices should uniformly occupy the space between the loudspeakers. Compare “beyond-the-speakers imaging,” “bunching,” “hole-in-the-middle.”

Stereo stage – The area between and behind the loudspeakers, from which most phantom images are heard.

Stopband- range of frequencies a filter does not run through pass along.

Sub-bass – Infrasonic bass.

Subjectivist – A person who has found that measurements don’t tell the whole story about reproduced sound. Compare “mystic,” “meter man,” “objectivist.”

Subliminal – Too faint or too subtle to be consciously perceived. Compare “inaudible.” See “listening fatigue.”

Subsonic – Slower than the speed of sound through air. Often used incorrectly to mean infrasonic.

Subtle – Barely perceptible on a very good system. See “audibility.”

Supersonic – Faster than the speed of sound through air. Sometimes used incorrectly to mean ultrasonic.

Sweet spot – That listening seat from which the best soundstage presentation is heard. Usually a center seat equidistant from the loudspeakers.

Switching amplifier- See class D amplifier

Switch-mode power supply (SMPS)- Power supply in which the transistors that deliver current to the load turn on and off rapidly rather than always conducting current. Contrast the linear power supply.


Tail – The reverberant decay of a sound in an acoustical space.

Tempo – The actual number of beats per minute in a musical performance. Compare “pace.”

Thick – Describes sodden or heavy bass.

Thin – Very deficient in bass. The result of severe attenuation of the range below 500Hz.

Tick – A high-pitched pulse characterized by a very sharp attack followed by a short “i” vowel sound. The most common background noise from analog discs.

Tight – 1) Bass reproduction that is well controlled, free from hangover, not slow. 2) Stereo imaging that is specific, stable, and of the correct width. 3) Describes a closely bunched image in A+B double-mono mode that occupies a very narrow space between the loudspeakers.

Tilt – 1) To aim the axis of a loudspeaker upward or downward. 2) Across-the-board rotation of an otherwise flat frequency response, so that the device’s output increases or decreases at a uniform rate with increasing frequency. A linear frequency-response curve that is not horizontal.

Timbre – The recognizable characteristic sound “signature” of a musical instrument, by which it is possible to tell an oboe, for example, from a flute when both are sounding the same note.

Timbre – The tone of a note

Timing – The apparent instrumental ensemble (synchronism) of a performance, which is affected by system speed. See “articulation,” “rhythm,” “pace.”

Tipped-up – Having a rising high-frequency response.

Tonality – In music, the quality of an instrument’s tone, often related to the key in which the music is written. In audio, mistakenly used in place of “tonal quality.”

Tonal quality – The accuracy (correctness) with which reproduced sound replicates the timbres of the original instruments. Compare “tonality.”

Top – The high treble, the range of audio frequencies above about 8kHz.

Total harmonic distortion (THD)- specification stating the amount of harmonic distortion in an audio component. Called “total” because it is the sum of all the individual harmonic-distortion components created by the component.

Tracking – The degree to which a component responds to the dictates of the audio signal, without lag or overshoot.

Transducer- any device that converts energy from one form to another. Microphones, loudspeakers, and phono cartridges are transducers. A microphone converts acoustic energy to electrical energy; a loudspeaker converts electrical energy to mechanical energy.

Transient- A sound that begins very suddenly, offer at high level; e.g., the sound of a snare drum struck sharply with a hard drumstick.

Transient – See “attack transient.”

Transient response- The ability of a component to accurately reproduce sudden, sharp sounds.

Transistor- Device made from solid semiconductor material that can amplify audio signals.

Transistor sound, transistory – See “solid-state sound.”

Transparent – Similar to clarity it is a clean clear open and detailed quality.

Transparency, transparent – 1) A quality of sound reproduction that gives the impression of listening through the system to the original sounds, rather than to a pair of loudspeakers. 2) Freedom from veiling, texturing, or any other quality which tends to obscure the signal. A quality of crystalline clarity.

Treble – The frequency range above 1.3kHz.

Triode- The simplest vacuum tube, employing just three elements: the cathode, plate, and control grid.

Tube sound, tubey – That combination of audible qualities which typifies components that use tubes for amplification: Richness and warmth, an excess of midbass, a deficiency of deep bass, outstanding rendition of depth, forward and bright, with a softly sweet high end.Turgid – Thick.

Tweak – 1) To fine-tune a system or component to the nth degree in pursuit of perfection. 2) A person who constantly does this in an ultimately vain effort to achieve absolute perfection.


Ultralinear- A method of operating a pentode vacuum tube that combines the output power of a pentode tube with the distortion characteristics of a triode tube. Invented by David Hafler and Herbert Keroes in 1951.

Ultrasonic – Beyond the upper-frequency limit of human hearing. Compare “supersonic.”

Unbalanced connection- connection method in which the audio signal is carried on two conductors, the signal and ground. Compare with balanced connection, in which the audio signal is carried on three conductors, two signal conductors and ground.

Uncolored – Free from audible colorations.

Underdamped – Pertains to the audible effects of inadequate woofer damping. See “damping.”

Upper bass – The range of frequencies from 80-160Hz.

Upper highs, upper treble – The range of frequencies from 10-20kHz.

Upper middles, upper midrange – The range of frequencies from 650-1300Hz.

Usable response – The frequency limits between which a device sounds as if it is essentially linear, regardless of how it measures.

User interface- The controls and displays on a product and their ease of use.


Vacuum tube- Device for amplifying audio in which the active elements are enclosed in a glass envelope devoid of air.

Voice coil- loop of wire wrapped around a bobbin positioned in the center of a loudspeaker driver through which flows current from the power amplifier.

Volt (V)- unit of electromotive force. The difference in potential required to make one ampere of current flow through one ohm of resistance. See also voltage.

Voltage- analogous to electrical pressure. Voltage exists between two points when one point has an excess of electrons in relation to the other point. A good example is a battery: its negative terminal has an excess of electrons in relation to its positive terminal. If you connect the piece of wire between the battery’s positive and negative terminals, voltage pushes current through the wire. One volt across one ohm of resistance produces a current of 1 ampere.

Voltage source- a power amplifier that can maintain its output voltage regardless of the load impedance.

Vowel coloration – A form of midrange or low-treble coloration which impresses upon all program material a tonal “flavor” resembling a vowel in speech.


Warm – The same as dark, but less tilted. A certain amount of warmth is a normal part of musical sound.

Warm/warmth – Engaging vocals, bumped mid bass and clear and lush midrange.

Watt (W)- unit of electrical power defined as the power dissipated by one ampere of current flowing through one ohm or resistance

Wavelength- The distance between successive cycles of a sinewave or other periodic motions.

Weight – 1) The feeling of solidity and foundation contributed to music by extended, natural bass reproduction. 2) The emphasis assigned to a subjective term by a qualifier.

Weighting curve- A filter applied to noise or sound-pressure-level (SPL) measurements that approximates the perceived loudness or noise level so that the measurement better correlates with subjective experience.

Width – The apparent lateral spread of a stereo image. If appropriately miked when recorded, a reproduced instrument should sound no wider or narrower than it would have sounded originally. See “stereo spread.”


XLR jack and plug- three-pin connector that usually carries a balanced audio signal.


Zero-crossing distortion- discontinuity in a musical waveform in a push-pull amplifier at the point where one transistor turns off and its complementary pair turns on.


Editor – Professor Mark Waldrep