Xoro HXS 532 - Инструкция (Страница 20)

SOUND GLOSSARY
A 3
A ( )
A
C
MPLIFIER AMP
MPLIFIER CLASSES
See Dolby Digital
A device which increases or boosts the level of an
input signal by increasing its amplitude. Amplifiers
typically increase voltage, current or both.
Audio power amplifiers are classified primarily by
the design of the output stage. Classification is
based on the amount of time the output devices
operate during each cycle of signal swing. Also
defined in terms of output bias current (the amount
of current flowing in the output devices with no
signal).
The key ingredient of class A
operation is that both devices are
always on. There is no condition
where one or the other is turned off.
Class A amplifiers are large, heavy
and run very hot. The positive effect
is that class A designs are inherently
the most linear, with the least amount
of distortion.
.
Class A
Class B
Class AB
Class D
Class G
B
.
.
.
The key ingredient of class
operation is that current flow in a
specific output device is zero when
not stimulated with an input signal
Due to this operation, class B
designs show high efficiency but poor
linearity around the crossover region.
operation allows both devices to be
on at the same time (like in class A),
but just barely. The output bias is set
so that current flows in a specific
output device appreciably more than
a half cycle but less than the entire
cycle. That is, only a small amount of
current is allowed to flow through
both devices It is this combination of
good efficiency (around 50%) with
excellent linearity that makes class
AB the most popular audio amplifier
design.
operation is switching, hence the
term switching power amplifier. Here
the output devices are rapidly
switched on and off at least twice for
each cycle. Class D operation is
theoretically 100% efficient
operation involves changing the
power supply voltage from a lower
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ADDENDUM
level to a higher level when larger
output swings are required. Class G is
becoming common for pro audio
designs
operation takes the class G design one
step further and actually modulates the
higher power supply voltage by the
input signal. This allows the power
supply to track the audio input and
provide just enough voltage for optimum
operation of the output devices. The
efficiency of class H is comparable to
class G designs.
The 'level' (perceived as 'volume') of an electrical or
acoustic signal. Shown as the value of the vertical
axis on a typical graph of a sound wave.
The total frequency range of any system. Usually
specified as something like: 20
20,000 Hz plus or
minus 3 d .
A multi-chambered ported system.
An electric circuit designed to pass only middle
frequencies.
Lower register of pitch; also a stringed musical
instrument designed to play low frequency sounds;
also a voice lower in pitch than a baritone.
A type of loudspeaker that uses a port or duct to
augment the low-frequency response. Opinions vary
widely over the "best" type of bass cabinet, but much
has to do with how well a given design, such as a
bass reflex is implemented.
In home theater, sound decoded from the stereo
signal sent to a speaker mounted in front of the
listener, specially designed to enhance voices and
sound effects from a movie soundtrack. Used in car
audio to help offset skewed stereo imaging due to
seating positions in the automotive environment.
In a stereo system, the level balance between left and
right channels. Properly balanced, the image should
be centered between the left-right speakers. In a
.
~
B
Class H
AMPLITUDE
BANDWIDTH
BAND-PASS ENCLOSURE
BAND-PASS FILTER
BASS
BASS REFLEX
CENTER CHANNEL
CHANNEL BALANCE