Mackie 1402 VLZ Owner's Manual page 38

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 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 sec-
ond.
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 posi-
tions of the slide pots give a graphic
representation 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 electrical
practices to ensure a safely grounded system.
Never remove or disable the grounding 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 op-
erate safely with a good safety ground. If you
have noise in your system due to technical
grounding problems, check your manual for
wiring tips or call technical support. Never dis-
able 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.