6. APPLICATION NOTES
Parameter related to the transient response of
the control circuit are important for distortionfree
processing. These time constants are allways
adaptive controlled without remarkable
limitation of parameter range. This is caused by
the presence of transient pulses in allmost each
kind of programme material. The algorithm has
to guarantee best reaction for fast increasing
level of transient signals anytime even if
classical music with slow dying out
characteristic is processed. In all cases the
attack time of the limiter for very short transients
is zero.
Especially the release time of the control circuit
has more influence to the increase of loudness
as any other parameter. The ranging of time
constants in processing time groups reflects
this fact. The range for processing time shows
influence on release time parameter mostly.
The selection of the parameter PRO in the
limiter or compressor edit menu changes the
range of time constant values as follows:
parameter
range of
corresponds
PRO
processing time
to former preset
-------------------------------------------------------------------------------------------------
0
2 ms to 0.2 sec
1
5 ms to 0.5 sec
2
10 ms to 0.8 sec
3
15 ms to 1.2 sec
SPEECH
4
30 ms to 2.5 sec
POP
5
50 ms to 3.5 sec
6
70 ms to 5.0 sec
UNIVERSAL
7
100 ms to 6.0 sec
8 150 ms to 8.0 sec
CLASSIC
9 250 ms to 10.0 sec
SELECTION OF PARAMETERS TO INCREASE LOUDNESS
6.4
Signal compression and the loudness
enhancement of the digital audio signal
resulting from it can be achieved by combining
two dynamic range control processes: firstly,
the compression achieved by increasing small
and medium signal levels and secondly, linear
amplification combined with the inaudible
limitation of individual, remaining peak levels
with the limiter.
In the gain change mode the operation of
compressor and limiter can be observed on the
display. For smaller signal levels the
compressor causes additional amplification
which however decreases the higher the signal
level is . With full scale levels the compressor is
practically ineffective so that even an increase
of the RATIO will have no effect.
If you now increase the linear amplification
GAIN, individual peak levels are raised above
the limiter threshold and limited inaudibly. All
other signal components can however be
increased. If the gain is too large also medium
levels are treated by the limiter, which means
that the limiter then reduces the signals
continually and again reduces the additionally
applied amplification.
The display for Limiter-Gain-Reduction should
be in the region of 0...-4...-6 dB and should not
light up red continuously, so that a dynamic
limitation only applies to signal peaks. Then the
signal compression and therefore also the
increase of loudness is at its most effective.
operation manual accent2, chapter 6-Application notes- page 6-3