Inovonics DAVID IV 719 N, Инструкция по установке и эксплуатации

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The dB gain numbers shown beside each input gain slider are
handy for reference and have been scaled so that 0dB equates
to the program average level at nominal studio line level fig-
ures. This might be +4dBu for analog inputs or –20dBFS for
digital feeds. For example, a well-te4dBm program
line would suggest an
Analog Gain (dB):
setting of
–4.0dB
, and
digital program levels with a typical headroom allowance of
20dB (relative to 0dBFS) would need a
Digital Gain (dB):
figure of
0dB
. Again, the scaling holds true more for actual program ma-
terial than for steady-state tones.
THE HIGH-PASS FILTER
Subaudible
Noise
The DAVID IV is equipped with a steep high-pass filter to less-
en the modulation-robbing effects of unwanted subaudible
program audio components. The term ‘unwanted’ is the key-
word here, as “mega-bass” seems a mandatory part of any car
audio installation, and a “big bottom-end” characterizes the
sonic signature of nearly all contemporary music stations.
The high-pass setting is found in the
Processor
menus. The
front-panel OLED menu actually animates the filter action with
a stylized representation of the cutoff characteristic.
This filter is a 4
th
order (24dB/octave) high-pass, which may be
set for a turnover frequency (–0.15dB point in this case) be-
tween
20Hz
and
65Hz
. The factory default is
20Hz
, which is
probably a valid setting for any music format, unless you have
severe turntable rumble (say, what?), noisy studio air condition-
ing, do a lot of outdoor sports remotes in windy stadiums, or
have creditors pounding on the front door.
This high-pass function has been included in the DAVID IV de-
sign to define a low-frequency limit to the station airchain. But
the use of this high-pass filter should generally be considered a
Band-Aid® fix for problems that are best addressed at their
source.
OPTIMIZING “W INDOWED” AGC ACTION
Actually, factory-default settings, the ones used for the preced-
ing setup process, should work pretty well for nearly any
broadcast format. But there may be instances where they might
want to be changed.
Defeating
the AGC
Turning
AGC: Off
( Bypass on the OLED) is never a good idea
in everyday operation. The AGC presents downstream pro-
cessing stages with an input signal optimized for further pro-
cessing. AGC has been carefully engineered for intelligent re-
sponse to program material, taking into account both the peak
and average values of the audio signal. The only justification
for turning AGC off is for test purposes, or if the user is 100%