Glossary of pro audio terms

Glossary aliasing This is a type of caused during the This Glossary contains brief definitions of analog-to-digital conversion process. If the fre- many of the audio and electronic terms and quency of the analog exceeds one-half acronyms used in discussions of mixing the sampling , spurious and harmon- and recording. Many of the terms have other ics not present on the original signal may be meanings or nuances or very rigorous technical created (see Nyquist Theorem). Careful design definitions, which we have sidestepped here and filtering before the sampling stage can because we figure you already have a lot on reduce this aliasing to a minimum. your mind. If you’d like to get more , there are plenty of useful textbooks out there. We recom- assign mend the following titles: The Audio Dictionary In sound mixers, assign means to switch or by Glenn White, Tech Terms by Peterson & route a signal to a particular signal path or com- Oppenheimer, Handbook for Sound Engineers by bination of signal paths. Glen Ballou, Mackie Mixer Book by Rudy Tru- bitt, Pro Audio Reference by Dennis Bohn, and Sound Reinforcement Handbook by Gary Davis. attenuate

To reduce or make quieter. A aux

Short for Auxiliary. ACRONYM

An acronym for A Contrived Reduction Of auxiliary Nomenclature Yielding Mnemonics In sound mixers, supplemental equipment or features that provide additional capabilities to adiabatic the basic system. Examples of auxiliary equip- ment include: serial processors (equalizers, Literally, it means "not to pass through." In , limiters, gates) and parallel pro- describing the high- foam used inside cessors ( and delay). the HR Series studio monitors, it means that internal reflections within the cabinet are absorbed by the foam. In physical terms, it aux send means the mechanical of the sound A mixer bus output designed to send a signal to is converted into energy. an auxiliary processor or monitor system. A/D converter (ADC) aux return Analog-to-digital converter, a device that trans- A mixer input (sometimes a pair of inputs) with forms incoming analog signals into digital limited control capabilities, intended for bring- form. ing the output of an auxiliary processor or other -level source into the main mix bus. AFL Aux returns can sometimes be assigned to other buses in the mixer. An acronym for After Fade Listen, which is another way of saying post-fader solo .


B bus An electrical connection common to three or more circuits. In mixer design, a bus usually balanced input carries signals from a number of inputs to a mixing amplifier, just like a city bus carries peo- An input consists of two leads, neither of which ple from a number of neighborhoods to their is common to the circuit . This is a “dif- jobs. It comes from the British “omnibus”. ferential pair”, where the signal consists of the difference in between the two leads. Bal- anced input circuits can offer excellent rejec- tion of common-mode induced into the line. balanced output Cannon

In a classic balanced audio circuit, the output is A manufacturer of electrical connectors who carried on two leads (high or + and low or -) first popularized the three-pin connector now which are isolated from the circuit ground by universally used for balanced con- exactly the same impedance. nections. In sound , a Cannon connector is taken to mean a Cannon XLR-3 connector or A symmetrical balanced output carries the same any compatible connector. You can tell an signal at exactly the same level but of opposite audio geezer because he refers to this connector polarity with respect to ground. as “Cannon”. Today the term “XLR” is more A special case of a balanced output carries the common. signal on only one lead, with the other lead being at zero voltage with respect to ground, but at the same impedance as the signal-carry- cardioid ing lead. This is sometimes called impedance bal- Heart-shaped. In sound work, cardioid refers to anced. the shape of the sensitivity vs. direction plot for a particular style of directional microphone. A bandwidth cardioid mic rejects sound arriving from the rear. The band of that pass through a device with a loss of less than 3 dB, expressed in or in musical . Also see Q. channel A functional path in an audio circuit: an input bit channel, an output channel, a recording chan- nel, the left channel and so on. The smallest component of a digital word, rep- resented by either a one or a zero. channel strip bridged mono The physical realization of an audio channel on the front panel of a mixer; usually a long, verti- A mode of operation for a stereo amplifier that cal strip of controls. routes a single input to both channels, but inverts the signal on channel 2, thereby provid- ing twice the voltage of an individual output by chorusing connecting the speaker between the two posi- A -based effect available in some digital tive output terminals (the negative output ter- delay effects units and reverbs. Chorusing minals are not used). involves a number of moving delays and pitch shifting, usually panned across a stereo field. 3

Depending on how used, it can be lovely or cueing grotesque. In broadcast, stage and post-production work, to “cue up” a sound source (a record, a sound clipping effect on a CD, a song on a tape) means to get A form of severe audio distortion that results it ready for playback by making sure you are in from peaks of the attempting to the right on the “cue,” making sure the rise above the capabilities of the amplifier cir- level and EQ are all set properly. This requires a cuit. Seen on an , the audio peaks special monitoring circuit that only the mixing appear clipped off. To avoid clipping, reduce engineer hears. It does not go out on the air or the system in or before the gain stage in to the main mixing buses. This “cueing” circuit which the clipping occurs. Also see headroom. is the same as pre-fader (PFL) solo on a Mackie mixer, and often the terms are interchangeable. common mode A signal which is referenced to the circuit com- D mon , usually chassis ground. D/A converter (DAC)

This is a dynamics processor used to smooth Digital-to-analog converter, a device that trans- out any large transient peaks in an audio signal forms incoming digital signals into analog that might otherwise overload your system or form. cause distortion. The threshold and other parameters such as attack time, release time, and tire are adjustable. Damping factor is a number that represents the condenser ratio of the impedance of the load to the out- put impedance of the amplifier. In practical Another term for the terms, it is a of how well the amplifier generally known as a . In audio, con- can control the movement of a speaker's . denser often refers to a type of microphone that The greater the damping factor, the better its uses a capacitor as the sound pickup element. ability to control the cone's movement. A low Condenser require electrical damping factor (high amplifier output imped- to run internal amplifiers and maintain ance) allows a woofer to continue to move after an electrical charge on the capacitor. They are the signal stops, resulting in an indistinct and typically powered by internal batteries or mushy low response. A high damp- “phantom power” supplied by an external ing factor (200 or above) provides excellent source, such as a . control over woofers and pro- duces a tight, clean bass. console DAT Another term for a sound mixer, usually a large desk-like mixer. Tape is a recording/playback sys- tem where analog signals are converted to digi- tal form and stored on magnetic tape. It offers all the benefits of digital audio including low noise and wide . The ratio of the peak value to the RMS value. Musical signals can have peaks many higher than the RMS value. The larger the tran- sient peaks, the larger the crest factor.


DAW Commonly used to describe signal levels in consumer equipment. To convert dBV to dBu, Digital Audio Workstation is a dedicated add 2.2 dB. recording/editing software application and hardware system, used for hard disk (non-lin- ) random access recording and playback. (dB) Many DAWs are used with personal The dB is a ratio of measured in sim- using Windows® or Macintosh® operating ilar terms using a . Many audio systems, though some use their own proprietary system parameters measure over such a large computers. range of values that the dB is used to simplify the numbers. A ratio of 1000:1=60 dB. Since dB dB is a unitless , it doesn’t if it’s or dollars. (just try asking the chief engi- See decibel. neer for a 3 dB raise) When one of the terms in the ratio is an agreed upon standard value such as 1.23 V, 1 V or 1 mw, the ratio becomes an dBA absolute value, i.e., +4 dBu, -10 dBV or 0 dBm. Level (SPL) measured with an "A" weighting filter. delay

In sound work, delay usually refers to an elec- dBm tronic circuit or whose purpose it is to delay the audio signal for some short period A of power in an electrical of time. Delay can refer to one short repeat, a circuit, expressed in referenced to 1 series of repeats or the complex interactions of milliwatt. The “m” in dBm stands for “milli- delay used in chorusing or reverb. When .” In a circuit with an impedance of 600 delayed signals are mixed back with the original , this reference (0 dBm) corresponds to a sound, a great number of audio effects can be signal voltage of 0.775 VRMS (because 0.775 V generated, including phasing and flanging, dou- across 600 ohms equals 1 mw). bling, Haas precedence-effect panning, slap or slapback, , regenerative echo, chorusing dBu and hall-like reverberation. Signal time delay is central to many audio effects units. A unit of measurement of audio signal voltage in an electrical circuit, expressed in decibels ref- erenced to 0.775 VRMS into any impedance. detent Commonly used to describe signal levels within A point of slight physical resistance (a click- a modern audio system. Nobody is really sure if stop) in the travel of a knob or slide control. “u” stands for anything. Most knobs on Mackie mixers are detented to indicate their unity gain or centered position. dBv It’s handy in the dark.

A unit of measurement equal to the dBu no longer in use in the US, but sometimes still in Great Britain. It was too easy to confuse a dBv The bending of sound around an obsta- with a dBV, to which it is not equivalent. cle (Huygens Principle). The longer the wave- in comparison to the obstacle, the more dBV the wave will diffract around it.

A unit of measurement of audio signal voltage in an electrical circuit, expressed in decibels ref- erenced to 1 VRMS across any impedance.


dipping dynamic microphone

The opposite of peaking, of course, used in The class of microphones that generate electri- audio to describe the shape of a frequency cal signals by the movement of a coil in a mag- response curve. A dip in an EQ curve looks like netic field. Dynamic microphones are rugged, a valley, or a dip. Dipping with an equalizer relatively inexpensive, capable of very good per- reduces a range of frequencies. (See guacamole.) formance and do not require external power. dither dynamics processor

This is an interesting technique to reduce the A type of processor that only affects the overall audibility of low level noise in a digital record- amplitude level of the signal (sometimes as a ing. Low level random noise is added to the function of its frequency content), such as a before the sampling stage, reduc- compressor, expander, limiter, or gate. ing an effect called quantization error. dynamic range doubling The range between the maximum and mini- A delay effect, where the original signal is mum sound levels that a sound system can han- mixed with a medium (20 to 50 ms) delayed dle. It is usually expressed in decibels as the copy of itself. When used carefully, this effect difference between the level at peak clipping can simulate double-tracking (recording a voice and the level of the noise floor. or instrument twice). dry E Usually means without reverberation, or with- out some other applied effect like delay or cho- rusing. Dry is not wet, i.e., totally unaffected. echo

The reflection of sound from a such as a DSP wall or a floor. Reverberation and echo are terms that are often used interchangeably, but Processing can accomplish the in audio parlance a distinction is usually made: same functions found in analog signal proces- echo is considered to be a distinct, recognizable sors, but performs them mathematically in the repetition (or series of repetitions) of a word, digital domain, with more precision and accu- note, phrase or sound, whereas reverberation is racy than its analog counterpart. Since DSP is a a diffuse, continuously smooth decay of sound. software-based process, parameters and process- ing functions are easily changed and updated Echo and reverberation can be added in sound by revising the software, rather than redesigning mixing by sending the original signal to an elec- the hardware. DSP can be found in an out- tronic (or electronic/acoustic) system that mim- board effects device, such as a reverb or delay ics natural echoes, and then some. The added unit, or it can be integrated into a DAW or dig- echo is returned to the mix through additional ital mixing console. mixer inputs. dual mono effects device or

A mode of operation for a stereo amplifier that effect processor routes a single input to both channels, but still An external signal processor used to add reverb, allows independent level control over each delay, spatial or psychoacoustic effects to an amplifier output. audio signal. An effects processor may be used


as an insert processor (serial) on a particular Bass and treble controls on your stereo are EQ; input or subgroup, or it may be used via the so are the units called parametrics and graphics aux send/return system (parallel). See also echo, and notch filters. reverb. A lot of how we refer to has to do with what a graph of the EIN looks like. A flat response (no EQ) is a straight line; a peak looks like a hill, a dip is a valley, a Equivalent Input Noise. A specification that notch is a really skinny valley, and a shelf looks helps measure the “quietness” of a gain stage by like a plateau (or a shelf). The slope is the grade deriving the equivalent input noise voltage nec- of the hill on the graph. essary to obtain a given preamp’s output noise. Aside from the level controls, EQs are probably Numerically, it’s the output noise at a given the most powerful controls on any gain setting minus the gain. EIN is usually mea- mixer (no, the power switch doesn’t count!). sured at maximum gain and typically ranges from -125 to -130 dBm. EMI F

Electro-Magnetic Interference. This refers to current induced into the signal path as a result fader of an external magnetic field. In audio systems, this is usually manifested as a 60 Hz or 120 Hz Another name for an audio level control. hum or buzz (50 Hz or 100 Hz in 50 Hz sys- Today, the term refers to a straight-line slide tems). The source of this noise can be from a control rather than a rotary control. ground loop or from the signal wire coming too close to a strong magnetic field such as a trans- former or high-current linecord. family of curves

A composite graph showing on one chart sev- EQ eral examples of possible EQ curves for a given equalizer or equalizer section. Short for equalization. filter EQ curve A simple equalizer designed to remove certain A graph of the response of an equalizer, with ranges of frequencies. A low-cut filter (also frequency on the x (horizontal) axis and ampli- called a high-pass filter) attenuates frequencies tude (level) on the y (vertical) axis. Equalizer below its . There are also high- types and effects are often named after the cut (low-pass) filters, bandpass filters, which cut shape of the graphed response curve, such as both high and low frequencies but leave peak, dip, bell, shelf, or notch. of frequencies in the middle untouched, and notch filters, which remove a narrow band but equalization leave the high and low frequencies alone. Equalization (EQ) refers to purposefully chang- flanging ing the frequency response of a circuit, some- times to correct for previous unequal response A term for an effect similar in sound to phas- (hence the term, equalization), and more often ing. Before we had electronic delay units, flang- to boost or cut the level at certain frequencies ing was accomplished by playing two tape for sound enhancement, to remove extraneous machines in , then delaying , or to create completely new and differ- one slightly by rubbing a finger on the reel ent sounds. flange. Get it?


FOH hold, and release time are some of the adjust- able gate parameters. An acronym for Front Of House. See house and main house speakers. Nobody involved with audio ever goes to the Back of House graphic EQ because they never have time to drink enough A graphic equalizer uses slide pots for its boost/ beer. cut controls, with its operating frequencies evenly spaced through the audio . In a frequency perfect world, a line drawn through the centers of the control shafts would form a graph of the The number of times an event repeats itself in a frequency response curve. Or, the positions of given period of time. Generally the time period the slide pots give a graphic representation of for audio frequencies is one second, and fre- boost or cut levels across the frequency spec- quency is measured in cycles per second, abbre- trum. Get it? viated Hz, honoring the physicist Dr. (who did not invent the rental car). One Hz is one . One kHz (kilo- ground hertz) is 1000 cycles per second. Also called . Ground is defined as the The range is generally consid- point of zero voltage in a circuit or system, the ered to be 20 Hz to 20, 000 Hz. This covers the reference point from which all other fundamental pitch and most of musi- are measured. cal instruments. In electrical power systems, ground connec- tions are used for safety purposes, to keep equipment chassis and controls at zero voltage and to provide a safe path for errant currents. G This is called a safety ground. Maintaining a good safety ground is essential to prevent elec- trical shock. Follow manufacturer’s suggestions gain and good electrical practices to ensure a safely grounded system. Never remove or disable the The measure of how much a circuit amplifies a grounding pin on the power cord. signal. Gain may be stated as a ratio of input to output voltage, current or power, such as a - In sensitive electronic equipment, tiny currents age gain of 4, or a power gain of 1.5, or it can and voltages riding on the ground (so it’s not be expressed in decibels, such as a line amplifier truly zero volts) can cause noise in the circuits with a gain of 10 dB. and hamper operation. Often a ground separate from the power ground is used as the reference point for the electronics, isolating the sensitive gain stage electronics from the dirty power ground. This is called a technical ground. An amplification point in a signal path, either within a system or a single device. Overall sys- audio equipment is designed to main- tem gain is distributed between the various gain tain a good technical ground and also operate stages. safely with a good safety ground. gate ground loop

A dynamics processor that automatically turns A ground loop occurs when the technical off an input signal when it drops below a cer- ground within an audio system is connected to tain level. This can reduce the overall noise the safety ground at more than one place. This level of your mix by turning off inputs when forms a loop around which unwanted current they are not in use. Threshold, attack time, can, and does flow, causing noise in the audio


system. Never disable the safety ground in an Hz attempt to solve hum problems. Short for Hertz. guacamole Just kidding (see dipping). I

H impedance

The A.C. resistance, , and induc- tance in an electrical circuit, measured in ohms. Haas precedence effect In audio circuits (and other ac circuits) the A psychoacoustic effect in which the time of impedance in ohms can often be much differ- arrival of a sound to the left and right ent from the circuit resistance as measured by a affects our of direction. If a signal is dc ohmmeter. presented to both ears at the same time and at Maintaining proper circuit impedance relation- the same , it appears to be directly in ships is important to avoid distortion and mini- front of us. But if the signal to one ear, still at mize added noise. Mackie input and output the same volume, is delayed slightly, the sound impedances are set to work well with the vast appears to be coming from the earlier (non- majority of audio equipment. delayed) side. input module headroom A holdover from the days when the only way The difference between nominal operating level that real consoles were built was in modular and peak clipping in an audio system. A mixer fashion, one channel per module. See channel with a nominal operating level of +4 dBu and a strip. maximum output level of +22 dBu has 18 dB of headroom. Plenty of room for surprise peaks. insert Hertz Noun – a place where a signal path can be bro- ken and a processing device placed in line with The unit of frequency, equal to 1 cycle per sec- the signal. It’s usually a TRS jack with one con- ond. Abbreviated Hz. kHz 1000 Hz, and is usu- ductor being an output (send) and the other ally pronounced “kay”(with “Hertz” implied) being an input (return). The jack is wired with a by sound professions who ask for “a little more normalled connection so that with nothing two and a half K” when they want you to boost plugged in, the send and return are connected 2.5 kHz. together, as if it wasn’t even there. In Mackie mixers, the insert jacks are wired with tip as house send, ring as return, and sleeve as ground. Verb – we don’t want to go there. In Sound Reinforcement parlance, “house” refers to the systems (and even persons) respon- sible for the primary sound reinforcement in a given hall, building, arena or “house.” Hence J we have the house mixer or house engineer, the house mix, the house mix amps, the main house speakers and so on.


may have several master controls, which may K be slide faders or rotary controls.

knee mic amp See mic preamp. A knee is a sharp bend in a curve (an EQ fre- quency response or compressor gain curve) not unlike the sharp bend in your leg. mic level

The typical level of a signal from a microphone. A mic level signal (usually but not always com- L ing from a microphone) is generally lower than -30 dBu. With a very source (a pin drop- ping?) the signal can be -70 dBu or lower. level Some microphones, notably vintage or vintage- style condenser mics, deliver a higher signal Another word for signal voltage, power, level than this for the same sound pressure strength or volume. Audio signals are some- level. A “hot” mic output level isn’t necessarily times classified according to their level. Com- a measure of the microphone’s quality, it’s just monly used levels are: microphone level (-40 an option that the designer chose. dBu or lower), instrument level (-20 to -10 dBu), and (-10 to +30 dBu). mic pre line level Short for mic preamp.

A signal whose level falls between -10 dBu and +30 dBu. mic preamp Short for microphone preamplifier. An ampli- fier whose job is to bring the very low micro- M phone level signal up to line level, or in the case of a mic preamp built into a mixer, the mixer’s internal operating level (approximately main (house) speakers 0 dBu). Mic preamps often have their own volume con- The main for a sound reinforce- trol, called a trim control, to properly set the ment system. These are usually the largest and gain for a particular source. Setting the mic loudest loudspeakers, and are usually posi- preamp gain correctly with the trim control is tioned so that their sound seems to come from an essential step in establishing good signal-to- the of the main stage. noise ratio and sufficient headroom for your mix. mains MIDI Short for main or house speakers in a sound rein- forcement system. Acronym for Digital Inter- face. MIDI is the industry’s standard serial protocol for the interface master and control of musical instruments. A control affecting the final output of a bus on which one or more signals are mixed. A mixer

10 mixer “Why did you mult the flanger into every input in the board?” An electronic device used to combine various audio signals into a common output. Different from a blender, which combines various fruits into a common libation. N monaural noise Long for mono. Literally, pertaining to or hav- ing the use of only one ear. Whatever you don’t want to hear. Could be hum, buzz or hiss; could be crosstalk or digital In the audio field, monaural describes a signal hash or your neighbor’s stereo; could be white or system which carries audio information on a noise or or noise; or it could single channel with the intent of reproducing it be your mother-in-law reliving the she had from a single source. One microphone is a her gallstone removed. mono source; many microphones mixed to one channel is a mono mix; a stereo (or, to be picky, a two-channel) mix of many microphones panned left and right is a stereo mix of mono sources. The residual level of noise in any system. In a well designed mixer, the noise floor will be a Monaural listening, and therefore mono com- quiet hiss, which is the thermal noise generated patibility of a stereo mix, is more important by bouncing around in and than you may realize. Most people hear televi- semiconductor junctions. The lower the noise sion audio in mono. Most are floor and the higher the headroom, the more mono. usable dynamic range a system has. monitor normal

In sound reinforcement, monitor speakers (or A wiring method which electrically ties together monitor or in-the-ear monitors) are two jacks or two poles of one jack so that in nor- those speakers used by the performers to hear mal operation, there is signal flow between themselves. In the and broadcast world, them. Inserting a plug breaks this connection, monitor speakers are often called foldback allowing the signal path to be modified. Normal speakers. In recording, the monitor speakers are wiring is common in patchbays and insert jacks. those used by the engineer and production staff to listen to the recording as it progresses. In zoology, the monitor lizard is the lizard that Nyquist sampling theorem observes the production staff as the recording progresses. Keep the lizard out of the mixer. This theorem states that, when an analog signal is converted to a digital signal, it must be sam- pled at a frequency that is at least twice the mono highest audio frequency present in the analog signal. If the audio frequency should exceed Short for monaural. one-half the sampling frequency, aliasing can result. Thus, if an analog-to-digital converter is mult sampling at 44.1 kHz, the audio signal should not exceed 22.05 kHz. Short for multiple. In audio work, a mult is a parallel connection (in a patch bay or with spe- cially built cables or wiring) used to feed an output to more than one input. A “Y” cable is a type of mult connection. Also used a verb, as in

11 bandwidth. “Semi” parametric EQs allow con- O trol of fewer parameters, usually frequency and gain (i.e., they have a fixed bandwidth, but vari- able center frequency and gain). P peaking The opposite of dipping, of course. A peak is an EQ curve that looks like a hill, or a peak. Peak- ing with an equalizer amplifies a band of fre- PA quencies. Acronym for Public Address. Today, people who work with PA systems like to say they’re PFL working in “sound reinforcement”. See SR. An acronym for Pre Fade Listen. Broadcasters would call it cueing. Sound folks call it being pan, pan pot able to solo a channel with the fader down. Short for panoramic potentiometer. A pan pot is used to position (or even dynamically move) phantom power a monaural sound source in a stereo mixing field by adjusting the source’s volume between A system of providing electrical power for con- the left and right channels. Our ste- denser microphones (and some electronic reo position by this difference in loud- pickup devices) from the microphone input ness when the sound strikes each ear, taking jack. The system is called phantom because the into account time delay, spectrum, ambient power is carried on standard microphone audio reverberation and other cues. wiring in a way that is “invisible” to ordinary dynamic microphones. Mackie mixers use stan- dard +48 volt DC power, switchable on or off. parallel mono Most quality condenser microphones are A mode of operation for a stereo amplifier that designed to use +48 VDC phantom power. routes a single input to both channels, but Check the manufacturer’s recommendations. combines the outputs of both channels into a Generally, phantom power is safe to use with single output by strapping the positivie output non-condenser microphones as well, especially terminals together, thereby providing twice the dynamic microphones. However, unbalanced current of an individual output. microphones, some electronic equipment (such as some microphone receivers) and some ribbon microphones can short out the patchbay phantom power and be severely damaged. A collection of usually a large number of jacks Check the manufacturer’s recommendations allowing convenient access to various points in and be careful! a system’s interconnect wiring. A patchbay can make re-routing signals very convenient with- out having to fish around with cables in the back of racks or consoles. See spaghetti. The time relationship between two signals, expressed in degrees around a . 0 and 360 degrees represents an in-phase relationship – parametric EQ both signals change in the same way at the A “fully” parametric EQ is an extremely power- same time. Anything else is out of phase. ful equalizer that allows smooth, continuous, 180 degrees out of phase is a special case which, and independent control of each of the three for a continuous , means that at any primary EQ parameters: frequency, gain, and given time the two signals have the same ampli-

12 tude but are opposite in polarity. The two legs post-fader of a differential output are 180 degrees out of phase. The phase reverse switch found on some A term used to describe an aux send (or other mixers or mic preamps actually reverses the sig- output) that is connected so that it is affected nal polarity. by the setting of the associated channel fader. When out-of-phase signals are mixed, there will Sends connected this way are typically (but not be some cancellation at certain frequencies, the always) used for effects. A post-fader output frequencies and the of cancellation from a mixer channel usually is also post-EQ. If being a function of the amount of phase shift pain persists, see your mixer’s block diagram. and the relative amplitude of the signals. Atten- Also see pre-fader. tion to mic placement and careful listening will allow you to use this effect creatively. pot, potentiometer

In electronics, a variable that varies the phasing potential, or voltage. In audio, any rotary or A dynamic effect in which the phase relation- slide control. ship between the fundamental and components of a sound is continually chang- pre-fader ing. This is done by passing the signal through an automatically sweeping filter. The effect is A term used to describe an aux send (or other often simulated by mixing original signal with a output) that is connected so that it is not delayed (1 to 10 ms) version of itself. The time affected by the setting of the associated channel of the delay is slowly varied, and the combina- fader. Sends connected this way are typically tion of the two signals results in a dramatic (but not always) used for monitors (foldback). moving comb-filter effect. A comb filter can be See post-fader. found in your back pocket. phone jack The property of many directional microphones Ever see those old switchboards with to accentuate their bass response when the hundreds of jacks and patch cords and plugs? source-to-mic distance is small, typically three Or the plug on the end of a headphone cable? inches or less. Singers generally like this effect Those are phone jacks and plugs, now used even more than in the shower. widely with musical instruments and audio equipment. A phone jack is the female connec- tor, and we use them in 1/4” two-conductor (TS) and three-conductor (TRS) versions. Q phone plug Q The male counterpart to the phone jack, right above. A way of stating the bandwidth of a filter or equalizer section. An EQ with a Q of .75 is broad and smooth, while a Q of 10 gives a nar- phono jack row, pointed response curve. To calculate the value of Q, you must know the center fre- Short for RCA phono jack. quency of the EQ section and the frequencies at which the upper and lower skirts fall 3 dB phono plug below the level of the center frequency. Q equals the center frequency divided by the dif- Short for RCA phono plug. ference between the upper and lower 3 dB- down frequencies. A peaking EQ centered at 10

13 kHz whose -3 dB points are 7.5 kHz and 12.5 can do it right on the front panel of many kHz has a Q of 2. effects units, or you can route the delay return back into itself on your mixer. Can be a great quantization deal of fun at parties. Regeneration is also a fancy name for . The digital representation of an analog signal Feedback makes oscillators work and reduces involves sampling the amplitude of the signal distortion in amplifiers. Feedback in sound at a fast rate. Quantization is the measurement reinforcement systems, a form of of the amplitude at the time of each sample, itself, makes you popular with dogs and unpop- expressed is a digital word. Where an analog sig- ular with musicians and audience alike. nal will be continuous as if it were going up a smooth path, quantization will have discrete steps (similar to stair steps). return A return is a mixer line input dedicated to the task of returning processed or added sound R from reverb, echo and other effects devices. Depending on the internal routing of your mixer and your own inclination, you could use returns as additional line inputs, or you could RAM route your reverb outputs to ordinary line inputs rather than the returns. Random Access Memory is a type of memory that can be read from and written to. reverberation, reverb RCA phono jack The sound remaining in a room after the source of sound is stopped. It’s what you hear in a Long for RCA jack or phono jack. An RCA large tiled room immediately after you’ve phono jack is an inexpensive connector clapped your hands. (female) introduced by RCA and originally used to connect to receiv- Reverberation and echo are terms that are often ers. The phono jack was (and still is) widely used interchangeably, but in audio parlance a used on consumer stereo equipment and video distinction is usually made: reverberation is equipment but was quietly fading into obscu- considered to be a diffuse, continuously rity in the professional and semi-professional smooth decay of sound, whereas echo is one or sound world. Then phono jacks began cropping more distinct, recognizable repetitions of a up in early project-studio multitrack recorders, word, note, phrase or sound which decreases in which (unfortunately) gave them a new lease on amplitude with every repeat. life. Since so many stereo recorders are fitted Reverberation and echo can be added in sound with them, we decided we’d have to put a cou- mixing by sending the original sound to an ple on our mixers for your convenience. But electronic (or electronic/acoustic) system that make no mistake: the only thing that the mimics natural reverberation, or worse. The phono jack (or plug) has going for it is low cost. added reverb is returned to the blend through additional mixer inputs. RCA phono plug Highly reverberant rooms are called live; rooms with very little reverberation are called dead. A The male counterpart to an RCA phono jack. sound source without added reverb is dry; one with reverb or echo added is wet. regeneration

Also called recirculation. A delay effect created by feeding the output of a delay back into itself to cause a delay of the delay of the delay. You 14 RFI effects devices. Mackie mixers call it an Aux Send. Interference. that often results from sparking cir- cuits. This can be manifested in a number of shelving ways in audio systems, but is usually evident as A term used to describe the shape of an equal- a high-frequency buzz or hash sound. izer’s frequency response. A shelving equal- izer’s response begins to rise (or fall) at some ROM frequency and continues to rise (or fall) until it reaches the shelf frequency, at which point the Read only memory is a type of computer mem- response curve flattens out and remains flat to ory that cannot be written to, but only read the limits of audibility. If you were to graph the from. response, it would look like a shelf. Or more like a shelf than a hiking boot. See also peaking RMS and dipping. An acronym for , a conven- signal-to-noise ratio (S/N) tional way to measure the effective average value of an audio signal or other AC voltage. This is a specification that describes how much Most AC voltmeters are calibrated to read RMS noise an audio component has compared to the volts, though on many meters that calibration signal. It is usually expressed in dB below a is accurate only if the waveform is sinusoidal. given output level. slap, slapback

S A single-delay echo without any repeats. Also see echo. Sa value solo A measure of the relative liveness of a room. A low Sa means a very live room, and a high Sa Italian for alone. In audio mixers, a solo circuit means a dead room. S = the total allows the engineer to listen to individual chan- of the room, and a = the average nels, buses or other circuits singly or in combi- coefficient of all the surfaces. nation with other soloed signals. sampling frequency sound reinforcement

This is the rate at which an analog signal is sam- A system of amplifying acoustic and electronic pled during the analog-to-digital conversion sounds from a performance or so that a process. The sampling rate used for compact large audience can hear clearly. Or, in popular discs is 44.1 kHz, but professional recordings music, so that a large audience can be excited, are often sampled at higher sample rates, such stunned, or even partially deafened by the tre- as 96 kHz or even 192 kHz (that’s 192,000 sam- mendous amplification. Means essentially the ples per second!). same thing as PA (Public Address). send spaghetti

A term used to describe the output of a second- That mess of wires and cables in the back of ary mix of the input signals, typically used for your rack and/or console. You really can tame foldback monitors, headphone monitors or this.

15 SR T An acronym for Sound Reinforcement, which refers to the process (or a system for) amplify- ing acoustic and electronic sounds from a per- tinnitus formance or speech so that a large audience can hear clearly. Or, in popular music, so that a The ringing in the ears that often results from large audience can be excited, stunned or even prolonged to very loud sound levels. partially deafened by the tremendous amplifica- A sound in the ears, such as buzzing, ringing, or tion. The term “SR” is to “PA” (Public Address) whistling, caused by volume knob abuse! as the term “environmental cleanup technolo- gist” is to “garbage collector”. trim In audio mixers, the gain adjustment for the first amplification stage of the mixer. The trim Just as a is an angular unit of measure in control allows the mixer to accommodate the 2-dimensional space, so a is an angu- wide range of input signal levels that come lar unit of measure in 3-dimensional space from real-world sources. It is important to set ( angle). the trim control correctly; its setting determines the overall noise performance in that channel stereo of the mixer. See mic preamp. Believe it or not, stereo comes from a Greek TRS word that means solid. We use stereo or ste- reophony to describe the illusion of a continu- Acronym for Tip-Ring-Sleeve, the three parts of ous, spacious sound field that is seemingly a two-conductor (plus shield) phone plug. Since spread around the listener by two or more the plug or jack can carry two signals and a related audio signals. In practice, stereo often is common ground, TRS connectors are often taken to simply mean two channels. referred to as stereo or balanced plugs or jacks. Another common TRS application is for insert jacks, used for inserting an external processor surround sound into the signal path. Multi-channel audio playback systems in four, five, or six channel formats. Surround sound is TS typically found in movie theaters and home theater systems. Acronym for Tip-Sleeve, the two parts of a sin- gle conductor (plus shield) phone plug. TS con- nectors are sometimes called mono or sweep EQ unbalanced plugs or jacks. A 1/4” TS phone plug or jack is also called a standard phone plug An equalizer that allows you to “sweep” or con- or jack. tinuously vary the frequency of one or more sections. symmetrically balanced U

See balanced. unbalanced

An electrical circuit in which the two legs of the circuit do not have the identical impedance to ground. Often one leg is also at ground poten-

16 tial. Unbalanced circuit connections require only two conductors (signal “hot” and ground). W Unbalanced audio circuitry is less expensive to build, but under certain circumstances is more susceptible to noise pickup. wet

A signal with added reverberation or other unity gain effect like echo, delay or chorusing. A circuit or system that has its voltage gain adjusted to be one, or unity. A signal will leave a unity gain circuit at the same level at which it X entered – no amplification, but no loss either. In Mackie mixers, unity gain is achieved by set- ting all variable controls to the marked and usu- ally detented “U” setting. Mackie mixers are XDR optimized for best headroom and noise figures with all gain stages beyond the preamp set at Acronym for eXtended Dynamic Range. XDR unity gain. is collection of Mackie circuit design elements which contribute to the low noise, high head- room mic preamp circuit employed on many V Mackie mixers. XLR connector VLZ See Cannon.

Acronym for very low impedance, a Mackie design principle. VLZ is one of the most impor- tant reasons why inherent noise levels on Y Mackie mixing boards are so minuscule. Ther- mal noise is generated in all real world elec- tronic components that have impedance. By Y-Cable keeping the impedances within the mixer cir- cuitry low, Mackie keeps internal noise to a A cable with one input and two outputs, used minimum. to mult a source to two inputs. volume

The sound level in an audio system. Perhaps Z the only thing that some bands have too much of. Z

VRMS The electrical symbol for impedance. Acronym for Volts Root Mean Square. See RMS. zymurgy

The science of brewing, an important part of Mackie technology since the factory is located less than a from the Hook brewery. Besides, we needed something other than just plain “Z” to put in this A-to-Z glossary.

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