filtergraphic EQ
A simple equalizer designed to remove cer-A graphic equalizer uses slide pots for its
tain ranges of frequencies. A low-cut filterboost/cut controls, with its frequencies evenly
(also called a high-pass filter) reduces orspaced through the audio spectrum. In a per-
eliminates frequencies below its cutoff fre-fect world, a line drawn through the centers
quency. There are also high-cut (low-pass)of the control shafts would form a graph of
filters, bandpass filters, which cut both highthe frequency response curve. Get it? Or, the
and low frequencies but leave a band of fre-positions of the slide pots give a graphic rep-
quencies in the middle untouched, and notchresentation of boost or cut levels across the
filters, which remove a narrow band but leavefrequency spectrum.
the high and low frequencies alone.ground
flangingAlso called earth. Ground is defined as the
A term for phasing. Before digital delay ef-point of zero voltage in a circuit or system, the
fects units, phasing could be accomplished byreference point from which all other voltages
playing two tape machines in synchronization,are measured. In electrical systems, ground
then delaying one slightly by rubbing a fingerconnections are used for safety purposes, to
on the reel flange. Get it?keep equipment chassis and controls at zero
FOHvoltage and to provide a safe path for errant
An acronym for Front Of House. See housecurrents. This is called a safety ground.
and main house speakers.Maintaining a good safety ground is always
frequencyessential to prevent electrical shock. Follow
The number of times an event repeats itselfmanufacturerOs suggestions and good electri-
in a given period. Sound waves and the electri-cal practices to ensure a safely grounded
cal signals that represent sound waves in ansystem. Never remove or disable the ground-
audio circuit have repetitive patterns that rangeing pin on the power cord.
from a frequency of about 20 repetitions perIn computer and audio equipment, tiny cur-
second to about 20,000 repetitions per second.rents and voltages can cause noise in the
Sound is the vibration or combination of vibra-circuits and hamper operation. In addition to
tions in this range of 20 to 20,000 repetitions perproviding safety, ground provisions in these
second, which gives us the sensation of pitch,situations serve to minimize the pickup, detec-
harmonics, tone and overtones. Frequency istion and distribution of these tiny noise
measured in units called Hertz (Hz). One Hertzsignals. This type of ground is often called
is one repetition or cycle per second.technical ground.
gainQuality audio equipment is designed to
The measure of how much a circuit ampli-maintain a good technical ground and also
fies a signal. Gain may be stated as a ratio ofoperate safely with a good safety ground. If
input to output values, such as a voltage gainyou have noise in your system due to techni-
of 4, or a power gain of 1.5, or it can be ex-cal grounding problems, check your manual
pressed in decibels, such as a line amplifierfor wiring tips or call technical support.
with a gain of 10dB.Never disable the safety ground to reduce
gain stagenoise problems.
An amplification point in a signal path,ground loop
either within a system or a single device.A ground loop occurs when the technical
Overall system gain is distributed betweenground within an audio system is connected to
the various gain stages.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.
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ACEC
