Mackie 8-BUS Series, Руководство пользователя

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O w n e r ’ s M a n u a l
Glossary
A-3
effects devices
External signal processors used to add re-
verb, delay, spatial, or psychoacoustic effects
to an audio signal. An effects processor may be
used as an insert processor (serial) on a par-
ticular input or subgroup, or it may be used via
the aux send/return system (parallel). See also
echo, reverberation .
EIN
Equivalent Input Noise. Specification that
helps measure the “quietness” of a gain stage by
deriving the equivalent input noise voltage nec-
essary to obtain a given preamp’s output noise.
Typically ranges from –125 to –129.5 dBm.
equalization (EQ)
This refers to deliberately changing the fre-
quency response of a circuit, sometimes to
correct for previous unequal response (hence
the term, equalization), and more often to add or
subtract level at certain frequencies for sound
enhancement, to remove extraneous sounds, or
to create completely new and different sounds.
Bass and treble controls on your stereo are
EQ; so are the units called parametrics, graph-
ics, and notch filters.
A lot of how we refer to equalization has to
do with what a graph of the frequency response
would look like. A flat response (no EQ) is a
straight line; a peak looks like a hill, a dip is a
valley; a notch is a really skinny valley; and a
shelf looks like a plateau (or shelf—duh!). The
slope is the grade of the hill on the graph.
Graphic equalizers have enough frequency
slider controls to form a graph of the EQ right
on the front panel. Parametric EQs, like those
used in the Digital 8•Bus, let you vary several
EQ parameters at once. A filter is simply a
form of equalizer that allows certain frequen-
cies through untouched while reducing or
eliminating other frequencies.
Aside from the level controls, EQs are prob-
ably the second most powerful controls on any
mixer (no, the power switch doesn’t count!).
EQ curve
A graph of the response of an equalizer, with
frequency on the x (horizontal) axis and ampli-
tude (level) on the y (vertical) axis. Equalizer
types and effects are often named after the
shape of the graphed response curve, such as
peak, dip, shelf, notch, knee, and so on.
frequency
The number of times an event repeats itself
in a given period. Sound waves and the electri-
cal signals that represent sound waves in an
audio circuit have repetitive patterns that
range from a frequency of about 20 repetitions
per second to about 20,000 repetitions per sec-
ond. Sound is the vibration or combination of
vibrations in this range of 20 to 20,000 repeti-
tions per second, which gives us the sensation
of pitch, harmonics, tone, and overtones. Fre-
quency is measured in units called Hertz (Hz).
One Hertz is one repetition or cycle per second.
gain
The measure of how much a circuit ampli-
fies a signal. Gain may be stated as a ratio of
input to output values, such as a voltage gain
of 4, or a power gain of 1.5, or it can be ex-
pressed in decibels, such as a line amplifier
with a gain of 10 dB.
gain stage
An amplification point in a signal path,
either within a system or a single device. Over-
all system gain is distributed between the
various gain stages.
gate
This is a circuit that will automatically turn
off an input signal when the signal drops below
a certain level. This can reduce the overall noise
level of your mix by turning off noisy inputs,
such as old tube gear, effects pedals, or ambient
noise picked up by microphones. Threshold,
attack time, and release are some of the gate
adjustments available.
headroom
The difference between nominal operating
level and peak clipping in an audio system. For
example, a mixer operating with a nominal line
level of +4 dBu and a maximum output level of
+22 dBu has 18 dB of headroom. Plenty of
room for surprise peaks.
Hertz
The unit of measure for frequency of oscilla-
tion, equal to 1 cycle per second. Abbreviated
Hz, kHz is pronounced “kay-Hertz” and is an
abbreviation for kilohertz, or 1000 Hertz.
internal effects
The Digital 8•Bus comes with one internal
effects card, with the option of adding more. A
plate of chicken vindaloo will also yield plenty
of remarkable internal effects, many in the
audio frequency range.
level
Another word for signal voltage, power,
strength or volume. Audio signals are some-
times classified according to their level.
Commonly used levels are: microphone level
(–40 dBu or lower), instrument level (–20 to
–10 dBu), line level (–10 to +30 dBu), and
speaker level (+30 dBu and above).
line level
A signal whose level falls between –10 dBu
and +30 dBu.
mic level
The typical level of a signal from a micro-
phone. A mic-level signal (usually but not
always coming from a microphone) is generally
below –30 dBu. With a very quiet source (a pin