Operating instructions

OPTIMOD-AM DIGITAL INSTALLATION
2-11
link with bit-for-bit transparency. Because sample rate conversion is a
phase-linear process that does not add bandwidth, the 9400’s output sig-
nal will continue to be compatible with 32 kHz links even if it undergoes
intermediate sample rate conversions (for example, 32 kHz to 48 kHz to
32 kHz).
Grounding
Very often, grounding is approached in a “hit or miss” manner. But 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 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 pro-
vide common-mode rejection and prevent ground loops regardless of whether it
is driven from a balanced or unbalanced source.
The 9400 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 — prefera-
bly the source (output) end.
 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.
Power Ground
 Ground the 9400 chassis through the third wire in the power cord. Proper
grounding techniques never leave equipment chassis unconnected to power /
earth ground. A proper power ground is essential for safe operation. Lifting a
chassis from power ground creates a potential safety hazard.
Circuit Ground
To maintain the same potential in all equipment, the circuit (audio) grounds must be
connected together:
 Circuit and chassis ground should always be connected by setting the 9400’s
G
ROUND LIFT switch to its GROUND connect position.
 In high RF fields, the system is usually grounded through the equipment rack in
which the 9400 is mounted. The rack should be connected to a solid earth