Solidyne AUDIMAX 362, Руководство пользователя

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AUDIMAX 362
SOLIDYNE
reducing the high level passages, consequently
increases the relative level of the passages of low
level, and therefore the noise. This is a forced
consequence of the compression process that has
particular effect in the increasing of the ambient
noise of the microphones. In order to avoid that,
the Solidyne processors incorporate a linear
expander, previous to the compressor stage.
The concept of linear expander implies an
expander that works within a very wide range of
signals, below a threshold value. That means it
always expands within that range, for any level of
signal. That is to say that their curve of
transference, based on the input level, is a
straight line (from there the "linear" name). This
implies that by each 10 dB that the input level
reduces, the expander will reduce, for example,
13 dB. This happens for any input value, below
the threshold. Then if the input is reduced in 30
dB, the output will do it in 39 dB; that is to say that
the background noise has been reduced in 9 dB.
This way, the expander compensates the increase
of the noise that the compressor, like undesired
effect, will increase.
At this point, maybe you will be thinking that
DOES NOT HAVE SENSE to make an expander
of the signal and soon to compress it. You will
think, perhaps, that an effect cancels to the other.
But it’s not true for two reasons. First: the different
attack and recovery times. Second: multiband
compressors have elevated threshold, whereas
the linear expander has a very low threshold and
a linear behavior below the threshold. It means
that the actions do not cancel, because both
processes
are not complementary
.
The linear expander, to optimize its behavior, has
instantaneous attack and a fast recovery times.
Here is where the psychoacoustic concept “post-
pulse hearing inhibition” is used. This allows using
an expander with a quick recovery time, so that
the ear does not perceive it. The broadband
compressor that follows the expander has a very
slow recovery time. Therefore, with impulsive
signals, as the audio program, does not exist any
cancellation effect.
Another advantage of using a linear expander
previous to the processing is that an excellent
audible sensation of dynamic range is obtained.
In fact, recent studies have demonstrated that the
audible sensation produced by the level variations
of an audio signal, is related to the changes
happened in the first 50 milliseconds, and is little
dependent of the reached final value. This
implies that an expander in the short term is
perceived like a great dynamic range, whereas
the power sensation (and even the coverage area
of the radio transmitter) is related to the
AVERAGE ENERGY, which depends of the
compression of the energy level.
You can see that they are two concepts different.
With audio processors of conventional design, the
expander and the compression were antagonistic
concepts. This does not happen in the field of the
psychoacoustics processors.
Stage 3 – Level Input Control
The Audimax-362 has an automatic control for the
input gain. Manual adjustments are not necessary.
The
AGC
(Automatic Gain Control) guarantee that
the audio signal enters to the delicate multiband
compressors always with the same level, avoiding
variations on the transmitted signal.
The AGC is designed to work with input levels
from –10 dBu to +15 dBu, which qualifies to the
AudiMax to work with all types of audio consoles,
from DJ’s mixers to professional broadcasting
consoles!
Stage 4 – Multiband Compressors
The purpose of the multiband compressors is to
increase the perceived loudness sensation. The
human voice and music will sound more solid,
with better dynamic balance. Still more, the
increase of the average energy of the audio signal
is very considerable, increasing the coverage
area of the radio for A.M. and FM transmissions
(for more info visit www.solidynepro.com).
Multiband technology bases on the studies of
Stevens (ref 1.2.3) about the loudness of each
band frequency and the studies of Zwicker (ref 4)
about its relation with the Critics Bands of the
human ear. The integration time of the ear to
reach the maximum loudness is of the order of
200 milliseconds (ref 5). This time must carefully
be incorporated to the controls of the loudness
compressors, to obtain the desired effect. The
ear will perceive a greater loudness when the
band compressors increase the relative loudness
level.
The processor Orion 462 has frequency splitters
with Butterworth filters of 18 dB/octave that
divides the program signal in four frequency
bands: low, low-middle, high-middle, high. In this
form, the multiband compressor in independent
form processes each bank of frequencies. This
way is possible:
1.
To increase the total energy
, by the use of fast
compressors for bass and ultra-fast for treble. If