Inovonics DAVID IV 719 N, Инструкция по установке и эксплуатации

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headings to confirm that the AGC is active, with a correction
rate of 1.75dB/sec, a (maximum) AGC Gain of +18dB, and a
Window setting of 6dB.
Test Tones
…or Not?
Although a “zero-VU” test tone may certainly be used during
DAVID IV setup, input gain is most accurately set with actual
program material. Here’s why.
Audio levels are typically measured and monitored in any of
several different manners. The traditional US mechanical “VU”
meter and the European “PPM” (Peak Programme Meter) each
adhere to audio industry measurement standards based on ex-
haustive studies. But there are many knock-offs and alternative
level-indicating gizmos in use as well, few of which have trace-
ability to any recognized standard. Substandard meters may
have floppy mechanical movements or take the form of flashy
LED and other bargraph readouts, or they can be fancy and col-
orful computer screen displays.
But compliant or not, all these devices have their own response
to, and provide their own representation of, program peak and
average levels; that is, program dynamics. What’s more, board
operators lend their individual interpretations to what they see,
assuming that they are even paying attention to meters in the
first place.
Adjusting
Input Gain
From the
Setup
Webpage, or with the
Setup / Audio Input
front-
panel menu, grab the slider for whichever input you have se-
lected. With program material playing, adjust the appropriate
Digital Gain (dB):
or
Analog Gain (dB):
slider so that the AGC bar-
graph readout hovers around
0dB
most of the time.
NOTE: This is a bit more tedious using the Web interface be-
cause you must toggle back and forth to the
Processing
Webpage to see the results of your actions in
Setup
. Take your
time.
The DAVID IV AGC is a slow gain-riding function with a dual
correction rate. Don’t rush this process as there will be some
delay before the AGC meter settles-down each time the slider is
adjusted. Once the input level has been adjusted to keep the
AGC hovering around 0dB, you’ll know that AGC action is more
or less centered and working in its ‘sweet spot.’
There will, of course, be a range over which the AGC wanders; it
is not realistic to expect the bargraph to sit right at the 0dB
mark all the time. But over an extended period the indicator
should spend about as much time above 0dB as it does below.
If you have used a ‘zero-VU’ tone from your console for input
gain setup you will probably need to correct the setting once
you’re running actual program material. With the exception of
studio-smashed (over-processed) pop music, the average-to-
peak ratio of a test tone is lower than that of natural, unpro-
cessed speech and music.