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Ashly Parametric Equalizers SC-63 User Manual

Page 17

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DEFINITION OF TERMS AS USED IN THIS MANUAL

ACTIVE

Electronic circuits which use devices such as transistors and integrated

circuits, and which are capable of voltage and power gain as well as
loss. Circuits using only resistors, capacitors, transformers, etc., are
referred to as passive.

AMPLITUDE

The voltage level of a signal. May be measured in volts or decibels.
Generally corresponds to the volume or intensity of an audio signal.

BALANCED

A 3-wire circuit arrangement in which two conductors are designated as
signal lines (+ and -), and the third is a shield and chassis ground. The
signal lines are of opposite polarity at any given moment, and are of

equal potential with respect to ground. Balanced input amplifiers are
used on all Ashly SC series products to improve hum and noise rejection.

Jumpering signal minus (-) to ground provides an unbalanced input.

CENTER FREQUENCY

The frequency (or pitch) at which a filter is most effective. In a
parametric equalizer, it refers to the frequency where a particular

boost/cut control has maximum effect.

dB

A unit by which audio levels can be COMPARED. Often thoroughly

misunderstood are the concepts that decibels represent the level of a

signal compared to some reference level (15 dB cut means a certain level
less than a previous level --- the absolute level of the signal need not

be known), and that decibels are a logarithmic unit.

Some handy numbers to remember when dealing with decibels:

dBm

+3 dB = Double Power

+6 dB = Double Amplitude, Quadruple Power

+ 10 dB = 10X Power

+20 dB = 10X Amplitude,

100X Power

A unit

of

measurement in

decibels where 0

dBm = a

power

level of 1

m illiwatt

into a 600 ohm

load. Originally

defined

by the

telephone

company

to measure line levels.

dBV

Decibel Volts, an update of the dBm definition where 0 dBV = the same

voltage level as 0 dBm, but with no regard to power or impedance. 0 dBV =
0.778 Volts. This unit is much more appropriate for modern audio
equipment with high impedance inputs and low impedance outputs.

DISTORTION

Generally refers to ANY modification of an audio signal which produces
new frequencies which were not in the original. Examples are harmonic
distortion, where a circuit adds overtones to a fundamental signal, and

intermodulation or IM distortion, where two frequencies beat together to

produce sum and difference frequencies.

FEEDBACK

Generally refers to any process where an output is in some form routed
back to an input to establish a loop. Negative feedback tends to be be
self stabilizing, while positive feedback causes instability.

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