Mackie 1202 VLZ Owner's Manual page 36

filter
A simple equalizer designed to remove cer-
tain ranges of frequencies. A low-cut filter
(also called a high-pass filter) reduces or
eliminates frequencies below its cutoff fre-
quency. There are also high-cut (low-pass)
filters, bandpass filters, which cut both high
and low frequencies but leave a band of fre-
quencies in the middle untouched, and notch
filters, which remove a narrow band but leave
the high and low frequencies alone.
flanging
A term for phasing. Before digital delay ef-
fects units, phasing could be accomplished by
playing two tape machines in synchronization,
then delaying one slightly by rubbing a finger
on the reel flange. Get it?
FOH
An acronym for Front Of House. See house
and main house speakers.
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 second.
Sound is the vibration or combination of vibra-
tions in this range of 20 to 20,000 repetitions per
second, which gives us the sensation of pitch,
harmonics, tone and overtones. Frequency 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 10dB.
gain stage
An amplification point in a signal path,
either within a system or a single device.
Overall system gain is distributed between
the various gain stages.
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graphic EQ
A graphic equalizer uses slide pots for its
boost/cut controls, with its frequencies evenly
spaced through the audio spectrum. In a per-
fect world, a line drawn through the centers
of the control shafts would form a graph of
the frequency response curve. Get it? Or, the
positions of the slide pots give a graphic rep-
resentation of boost or cut levels across the
frequency spectrum.
ground
Also called earth. Ground is defined as the
point of zero voltage in a circuit or system, the
reference point from which all other voltages
are measured. In electrical systems, ground
connections are used for safety purposes, to
keep equipment chassis and controls at zero
voltage and to provide a safe path for errant
currents. This is called a safety ground.
Maintaining a good safety ground is always
essential to prevent electrical shock. Follow
manufacturer's suggestions and good electri-
cal practices to ensure a safely grounded
system. Never remove or disable the ground-
ing pin on the power cord.
In computer and audio equipment, tiny cur-
rents and voltages can cause noise in the
circuits and hamper operation. In addition to
providing safety, ground provisions in these
situations serve to minimize the pickup, detec-
tion and distribution of these tiny noise
signals. This type of ground is often called
technical ground.
Quality audio equipment is designed to
maintain a good technical ground and also
operate safely with a good safety ground. If
you have noise in your system due to techni-
cal grounding problems, check your manual
for wiring tips or call technical support.
Never disable the safety ground to reduce
noise problems.
ground loop
A ground loop occurs when the technical
ground within an audio system is connected to
the safety ground at more than one place. Two
or more connections will allow tiny currents to
flow in the loops created, possibly inducing
noise (hum) in the audio system. If you have
noise in your system due to ground loops, check
your manual for wiring tips or call technical
support. Never disable the safety ground to re-
duce noise problems.