Orban OPTIMOD-FM 8700, Operating Manual

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2-20
INSTALLATION ORBAN MODEL 8700i

If you are using an Orban 4000 Transmission Limiter, set field to
N
O
(so that
the AGC function in the 8700i continues to work). The Orban 4000 is a
transmission system overload protection device; it is normally operated be-
low threshold. It is not designed to perform an AGC or gain-riding function
and it cannot substitute for the AGC function in the 8700i.
Most of the processing structures in the 8700i control level with a prelim-
inary AGC (Automatic Gain Control). If you are using a suitable Automat-
ic Gain Control at the studio, the AGC in the 8700i 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.
6. Set input levels.
A) Prepare to adjust the Input Reference Levels.
a) Feed normal Program material to the 8700i.
Play program material from your studio, peaking at normal program lev-
els (typically 0VU if your console uses VU meters).
b) Locate to the Reference Levels screen ( S
YSTEM
S
ETUP
> Q
UICK
S
ETUP
5 ).
The Reference Level screen allows you to match the 8700i to the normal
operating level to be expected at the 8700i, so the 8700i’s AGC can oper-
ate in the range for which it was designed. There are separate settings
for the analog and digital inputs. If you provide both analog and digital
inputs to the 8700i, optimum adjustment is achieved when the same
amount of processing is indicated for either analog or digital inputs. This
will allow you to switch between analog and digital inputs without sud-
den level changes.
B) Using the S
ET
I
NPUT
T
O
field, set the input to A
NALOG
.
[Skip this step if you are not using the analog input.]
a) Adjust the A
NALOG
R
EFERENCE
L
EVEL
so that the meter reads an average of
10 dB gain reduction.
[

9 dBu to +13 dBu (VU), or –2 to +20 dBu (PPM)] in 0.5 dB steps
The
A
NALOG
R
EFERENCE
L
EVEL
VU
and
PPM
settings track each other with
an offset of 8 dB. This compensates for the typical indications with pro-
gram 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
8700i, set the
A
NALOG
R
EFERENCE
L
EVEL
to this level, but please verify it with
the steps shown directly below.
b) If the AGC gain reduction meter averages less than 10 dB gain reduction
(higher on the meter), re-adjust the A
NALOG
R
EFERENCE
L
EVEL
to a lower
level.
c) If the AGC gain reduction meter averages more gain reduction (lower on
the meter), re-adjust the A
NALOG
R
EFERENCE
L
EVEL
to a higher level.
This control has no effect on the AES3 digital input.
C) Using the S
ET
I
NPUT
T
O
field, set the input to D
IGITAL
or DANTE .