5. APPLICATION NOTES
If such a signal is compressed or limited in a dynamics
processor, problems will occur as the peak levels for high
frequencies do not represent the true values. The dynamics
processor causes a change in peak levels which would, however,
lead to a change in the treble content after passing through the
external deemphasis filter.
Prior to dynamic processing a signal recorded with emphasis
must therefore be linearized, i.e. pass through a digital
deemphasis filter. This filter in the
d 02
is automatically switched
on if the corresponding control bit is set in the AES/EBU or
S/PDIF format. If the filter is turned on, the colour of the AES
input LED will change to red.
The static characteristics of the
d 02
(see also fig. 2) usually
refers to the
digital
reference level 0 dBFS
(dB Full Scale). This
is useful for most applications of the dynamics processor as the
on-following digital recording system is supposed to be balanced
down to the final bit.
For applications using headroom the
d 02
can be adjusted to
another reference level of
0 ... -15 dBFS
in steps of 1 dB. The
limiter threshold and therefore the maximum output level are
determined by this digital reference level. This value is then also
the reference for the expander and limiter threshold values. The
static characteristics for a reference level of -9 dBFS are
illustrated in fig. 5.
The adjustment of the device to this reference level is achieved
with pushing DISPLAY and GAIN buttons at the same time (see
also chapter 2.4. and 3.).
5.3.
Working with
headroom
24
