6. APPLICATION NOTES
operation manual accent2, chapter 6-Application notes- page 6-1
APPLICATION NOTES
6
THE JÜNGER AUDIO DYNAMICS PROCESSOR PRINCIPLE
6.1
A change in the dynamic range of an audio
signal is a non-linear process. The gain of a
dynamic range processor is not constant as it is
with the gain of a linear amplifier. The gain
varies in time depending on the input signal and
depending on the specific control algorithm of
the dynamics processor. These variations in the
gain, which represent the real control process,
should take place without any bothersome side
effects such as pumping, signal distortion,
sound colouration or noise modulation, which
means they should be inaudible.
The main problem here is to react to fast
changes in the audio signal (transients) without
the control process being audible and
disturbing. The ability of a dynamic range
processor to react to rapid amplitude changes
depends directly on its attack time.
Long attack times do not cause modulation
distortions, but lead to overshoots because the
system is not fast enough to reduce the gain. A
short attack time minimizes the amplitude and
time of a possible overshoot, but a rapid gain
change has audible side effects such as "
clicks" caused by modulation products.
Traditional compressor and limiter designs only
have one control circuit with corresponding
attack and release times, which have to be
adjusted manually by the user. An optimal
setting of all parameters for dynamic range
processing with as little disturbance as possible
must be determined by listening and
comparing.
A lot of experience and also a lot of time is
necessary to get sufficient results. These
parameters , once found, are only the right
choice for a certain programme signal and must
be changed for other signals.
Dynamic range processors which split the audio
frequency spectrum into several bands, i.e.
which have a multi-band structure, have some
advantages over traditional compressor
designs. The dynamic control parameters in
each band are independent of one another and
can be set in such a way that a broad program
range can be processed well. Disruptive side
effects such as pumping and breathing can
largely be avoided. The disadvantage of this
system lies in the problem of rebuilding the
output signal, which is the sum of all filters
including those where dynamic changes have
taken place as part of the control process. The
output signal is always coloured and deviates
from the input signal in sound.
multi-loop principle
The dynamic range processor principle
developed by Jünger Audio makes it possible
to realise dynamics processors (compressor,
limiter, expander) with very high audio quality,
without signal discolouration, pumping or
breathing, without distortion and modulation
products - in short, with almost inaudible
processing - and they are very easy to use.
The Jünger Audio dynamics processors work
according to a Multi-loop principle, operating
with an interaction between several frequency
linear control circuits. The resulting attack and
release times of this system are variable and
adapted to the evolution of the input signal.
This allows relatively long attack times during
steady-state signal conditions but also very
short attack times when there are impulsive
input transients.
traditional compressor and limiter designs
delay time
The Multi-loop structure also permits a short
time delay between the control circuit and the
gain changing element. The gain control circuit
has time to preview the signal and become
active before it reaches the output. This is
particularly important for the limiter, which
provides a precisely leveled output signal
absolutely free of overshoots (clipping).
multi-band structure
With a digital signal processor, a large number
of parameters of the audio signal are evaluated
and there is a permanent, automatic
optimisation of the parameters of all control
circuits.