OPTIMOD-FM INSTALLATION
2-25
Control at the studio (such as an Orban 8200ST OPTIMOD-Studio or 464A
Co-Operator), the AGC in the 8400 should be defeated. This is so that the two
AGCs do not “fight” each other, and so they do not simultaneously increase
gain resulting in increased noise.
If you are using an Orban 4000 Transmission Limiter, set field to
No (so that
the AGC function in the 8400 continues to work). The Orban 4000 is a trans-
mission system overload protection device; it is normally operated below
threshold. It is not designed to perform an AGC or gain-riding function, and it
cannot substitute for the AGC function in the 8400.
7. Set Input Levels.
A) Adjust Input Reference Level.
a)
Feed normal Program material to the 8400.
Play program material from your studio, peaking at normal program levels
(typically 0VU if your console uses VU meters).
b) Locate
to the Reference Levels screen (System Setup: Quick Setup 5).
The Reference Level screen allows you to match the 8400 to the normal op-
erating level to be expected at the 8400, so the 8400’s AGC can operate in
the range for which it was designed. There are separate settings for the ana-
log and digital inputs. If you provide both analog and digital inputs to the
8400, optimum adjustment is achieved when the desired amount of process-
ing is indicated for either analog or digital inputs. This will allow you to
switch between analog and digital inputs without sudden level changes.
c)
Set the input to Analog and adjust Analog Reference Level.
[Skip this step if you are not using the analog input.]
d)
Adjust the Analog Reference Level so that the meter reads an average of 10 dB
gain reduction.
[−9 dBu to +13 dBu (VU), or –1 to +21 dBu (PPM)] in 0.5 dB steps
The
Analog Reference Level VU and PPM settings track each other with an
offset of 8 dB. This compensates for the typical indications with program
material of a VU meter versus the higher indications on a PPM.
If you know the reference VU or PPM level that will be presented to the
8400, set the
Analog Reference Level to this level, but please verify it with
the steps shown directly below.
If the
AGC gain reduction meter averages less than 10 dB gain reduction
(higher on the meter), re-adjust the
Analog Reference Level to a lower level.
If the
AGC gain reduction meter averages more gain reduction (lower on the
meter), re-adjust the
Analog Reference Level to a higher level.
This control has no effect on the AES/EBU digital input.
e)
Set the input to Digital and adjust Digital Reference Level.
[Skip this step if you are not using the digital input.]
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