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Glossary and Terms G Thru M
Gain - The
amount of increase in audio signal strength, often expressed in dB.
- A device that changes the gain of an amplifier or circuit,
often a knob that can be turned or a slide that can be moved up arid
Reduction - The working of a limiter or compressor
reducing gain during high-level passages.
Structure - The way in which the gain varies in the
stages or sections of an audio system.
Gate - A
dynamic processing device that turns a channel off or down when the
signal drops below a certain level.
Section - A ratio of height to width to length of a room
to achieve "good acoustics" and first recommended by the
ancient Greeks. The ratio is approximately the width 1.6 times the
height and the length 2.6 times the height
Equalizer - An device with several slides controlling
the gain of audio signal present which is within one of several
evenly spaced frequency bands (spaced according to octaves).
- A switch that breaks the connection between the ground point in
one circuit and the ground point in another circuit.
- An adapter that takes a three prong power cord and plugs
into a two prong outlet, used to disconnect the third (ground) pin
of the power outlet. WARNING: It can be VERY DANGEROUS to have no
ground connection to the case by using a ground lifter and not
grounding the unit by other means.
- A double grounding of a line or electronic device at two different
"ground" points of differing voltage.
Haas Effect -
Simply stated, a factor in human hearing where delay has a much
bigger effect on human perception of direction than level
Head Amp -
British name for Preamplifier (A low-noise amplifier designed to
take a low-level signal, such as the output of a tape head, and
bring it up to normal line level).
- 1) The level difference (in dB) between normal operating level and
clipping level in an amplifier or audio device. 2) A similar level
difference between normal tape operating level and the level where
the distortion would be 3%.
Limitation - An inability of the ear to hear important
characteristics of sound under certain conditions. Characteristics
that can be affected include pitch, level, clarity, presence and
The unit of frequency. Equivalent to cycles per second.
Hi-Z - An
abbreviation of the term High Impedance (Impedance of 5000 or more
Frequencies - The audio frequencies from 6000 Hz and
High Pass Filter
- A circuit that lets higher frequencies pass unchanged, while
reducing the amplitude of frequencies lower than a set point, and
reducing them at a fixed rate per octave. High pass filters,
for example, act to direct higher frequencies to satellite speakers
-- and keep lower frequencies minimal -- when one sets their size to
"small" in a surround system. In this particular case the
filter will usually pass frequencies above 80 Hz and attenuate those
below. High-pass filters in general, though, can act at any
frequency point for which they're designed.
Short for the term High Frequencies (the audio frequencies from 6000
Hz and above).
- A speaker or speaker enclosure where sound waves are put into a
narrow opening (by a speaker cone or driver) and the narrow opening
flairs out to a larger opening.
Hum - The 60
Hz power line current accidentally induced or fed into electronic
Hz - An
abbreviation for the term Hertz (the unit of frequency).
- Abbreviation of Integrated Circuit (A miniature circuit of many
components that is in small, sealed housing with prongs to connect
it into equipment).
An index signal (digital data that gives the machine information of
where selections start, their selection number, etc.) on a DAT or
- An abbreviation of the term Intermodulation Distortion (Distortion
caused by one signal beating with another signal and producing
frequencies that are both the sum and the difference of the original
The squaring of the waveform that happens in the conversion of
digital audio bits into analog signals.
Impedance - a
measure of the total opposition to current flow in an alternating
current circuit measured in ohms. When applied to speakers,
impedance is the load that a speaker places on the power
amplifier. A low impedance device draws a high current flow
from a source such as a power amplifier; higher impedance sources
This means that given the same
voltage level, a 4 ohm speaker will draw twice as much current as an
8 ohm speaker. This is because a speaker with half the
impedance level provide only half the resistance to the voltage
approaching them, and will let twice as much power through.
Amplifiers deliver more power into lower impedances -- up to twice
their rated power -- making speakers with a low impedance (lower
than 6-8 ohms) more difficult for amplifiers to drive.
Matching - Having or converting the output impetlance of
a device so thar it matches the impedance of the input it will feed.
In - Short
For "in the circuit," in other words "active."
Input - 1)
The jack or physical location of where a device receives a signal.
2) The signal being received by a device. 3) The action of receiving
a signal by a device.
Impedance - The opposition to current flow by the first
circuits of a device.
Overload - Sending too high of a signal level into a
device so that the first amplifler of the device overloads.
- A substance such as glass, air, plastic, etc., that will (for all
practical purposes) not conduct electricity.
Any device that allows one unit to work, drive or communicate with
another unit when they cannot do so by just feeding each other often
because the units are manufacturcd by different companies.
Distortion - Distortion caused by one signal beating
with another signal and producing frequencies that are both the sum
and the difference of the original frequencies.
Square Law - Simply stated, the fact that in an
un-obstructed area (like an open field) the sound pressure level
will drop to half-pressure (-6 dB) every time the distance to the
sound source is doubled.
I/O - Short
for "Input/Output' and referring to: 1) An in-line console
module that contains controls for the input section, output section
and monitor section. 2) A module in electronic gear containing input
and output amplifiers for the device. 3) A digital port (connector)
able to both receive digital data and output digital data. 4)
A card or separate unit that converts audio to digital audio for
input into a digital system and also do the reverse for the
Jack - A
connector mounted on the case of a device or on a panel.
- A series of jacks which have connections for most of the
inputs and outputs of the equipment in the control room.
LED - A
light that allows current to flow in one direction only and emits
light whenever a voltage of a certain level or beyond is applied to
The amount of signal strength; the amplitude, especially the average
Low-Frequency Oscillator (an oscillator that puts out an AC signal
between .1 Hz and 10Hz used for a control signal).
Limiter - A
protection circuit, either built into an amplifier or packaged as a
separate unit, that reduces signal amplitude above a fixed point so
that output cannot exceed a certain level, thus preventing damage
further down the signal path, whether to other audio equipment or to
Limiters work by monitoring outputs for excessive signal levels, and
when they sense it, feeding back control signals to an earlier part
of the circuit that lower the systems gain. This prevents signals
from clipping; ie, it fundamentally prevents square waves from
forming in the signal path.
Line - 1)
Short for line level. 2) A cable.
- An input designed to take a line level signal.
- An amplified signal level put out by an amplifier and used
as the normal level that runs through the interconnecting cables in
a control room.
- The condition of obtaining a change at the output of the device
which is proportional to the change occurring at the input.
Load - 1)
The opposition to the audio output signal of a device by the input
of the device being fed. 2) A resistor that would have the lowest
impedance the device was designed to feed into used during testing
of a device.
Impedance - The opposition to output current flow caused
by the input that it feeds.
Frequencies - 1) Any audio or audible frequency below
1kHz. 2) The range of bass frequencies below approximately 250 Hz.
Low Frequency Effects (LFE)
Channel - a separate channel, in Dolby Digital and DTS
formats, specifically for low frequency effects such as rumbles,
explosions, the hoof beats of thundering herds or the deep menacing
voices of villains in dark capes. The LFE channel is the
".1" in 5.1, 6.1, and 7.1 formats.
Listener Fatigue - A
sense of sonic irritation, often in the form of slight headache or
the sense of ones ears burning. Often experienced after long
periods of listening, the most common causes are high audio volume
accompanied by sonic distortions such as overly loud bass, overly
emphasized high frequency, or simple distortion in the reproduction
equipment and speakers.
Lobe - A point in
space where a speaker system generates maximum acoustic output due
to its multiple drivers output overlapping at crossover
frequencies. At the center of a lobe, output at those
frequencies rises slightly over 6 dB. The opposite
effect occurs in a null (see below).
Low Pass Filter - A
circuit that passes low frequencies and reduces the amplitude of
high frequencies above it at a fixed rate. For instance, when
one sets the low pass filter control on a subwoofer to 80 Hz, the
audio signal below that frequency is passed on to the subwoofer
driver unaltered, while the portion of the signal above 80 Hz is
attenuated. If the filter uses the standard 12 dB per octave
attenuation, the signal level at 160 Hz will be lower by 12 dB and
at 320 Hz, by 24 dB. As with high pass filters, low pass filters can
be designed to act anywhere in the audio frequency range.
The characteristic of hearing by which loud sounds prevent the ear
from hearing softer sounds of similar frequency.
MDF (Medium Density
Fiberboard) - A composite wood product used in many speaker
cabinets because of its acoustically inert properties.
- The control of one signal by another AC signal.
Noise - Noise that is present only when the audio signal
A group of circuits and controls that are mounted on a removable
housing; often on consoles, all of the controls and circuits for one
or two channels.
Shortened from Monophonic and meaning that there is only one sound
source or the signal was derived from one sound source.
Jack - Short for Multiple Jacks or Multiple Jack and
meaning: 1) a jack at the output of a device which is not normalled
so that plugging into the jack will allow the output to be sent to a
different input and the output will also feed the normal place it
feeds. 2) A set of jacks (or one of a set of jacks) with each
terminal wired to a corresponding terminal of another or other jacks
- A switch which turns off a channel, takes out a track signal from
the monitors, or which turns off the entire monitor signal.
& Granite Audio
Salem, OR 97303
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