Orban Optimod-PC 1101, Operating Manual

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OPTIMOD-PC INSTALLATION
2-19
meters or less), longer runs require use of 110
Ω
balanced cable like
Belden 1800B, 1801B (plenum rated), multi-pair 180xF, 185xF, or 78xxA.
Single-pair category 5, 5e, and 6 Ethernet cable will also work well if you
do not require shielding. (In most cases, the tight balance of Category
5/5e/6 cable makes shielding unnecessary.)
The AES3id standard is best for very long cable runs (up to 1000 meters).
This specifies 75
Ω
unbalanced coaxial cable, terminated in BNC connec-
tors. A 110
Ω
/75
Ω
balun transformer is required to interface an AES3id
connection to your Optimod’s digital input or output.
The digital input clip level depends on the setting on the D
IGITAL
1 I
NPUT
and D
IGITAL
2 I
NPUT
mixer controls. To avoid clipping, set these so that the
P
ROCESSOR MIXER
O
UTPUT
meters never indicate red.
A Backup function allows inputs to be programmed to automatically
mute unless digital lock is lost on another input. Such loss of lock causes
the backup input to be unmuted. You can arrange this function so that,
for example, loss of lock on digital input 1 causes digital input 2 to un-
mute, and loss of lock on both digital inputs causes the analog input to
unmute. This allows you to connect backup program sources to ordinarily
unused inputs and have the backup inputs activate automatically if the
primary program feed is lost.
Grounding
Very often, grounding is approached in a “hit or miss” manner. However, with care
it is possible to wire an audio studio so that it provides maximum protection from
power faults and is free from ground loops (which induce hum and buzz, and can
cause oscillation).
In an ideal system:
•
All units in the system should have balanced inputs. In a modern system with
low output impedances and high input impedances, a balanced input will
provide common-mode rejection and prevent ground loops—regardless of
whether it is driven from a balanced or unbalanced source.
OPTIMOD-PC has balanced inputs.
•
All equipment circuit grounds must be connected to each other; all equipment
chassis grounds must be connected together.
•
In a low RF field, cable shields should be connected at one end only—
preferably the destination (input) end. This prevents input noise should the
source become disconnected.
•
In a high RF field, audio cable shields should be connected to a solid earth
ground at both ends to achieve best shielding against RFI.
•
Whenever coaxial cable is used, shields are automatically grounded at both
ends through the terminating BNC or phono connectors.