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104 Appendix E: Best Grounding Practice
VeniceU
Operator Manual
connecting balanced external processing equipment to the insert points, the connection
method described in this section should be adopted so as to benefit from the CMR of the
external unit.
For an example of how to wire a ground referenced insert, see Figure 2 on page 15.
Unbalanced connections
Ground loops with unbalanced signals are more difficult to deal with, but there are
several good techniques available. Firstly, many sources of unbalanced signals are
battery or class 2 powered devices without a safety earth connection, thus ground loops
are not being generated. These signals can be connected via single conductor cables
with an overall ground shield and should not present any problems.
Signal ground lift
Older processing equipment is often unbalanced, but even if it is a class 1 device, very
often the internal signal ground can be isolated from the safety ground. This is
normally achieved by setting an external "ground lift" switch or breaking an internal
link. Refer to the equipment’s manual and qualified technicians for advice on any such
internal links. If ground isolation is available it should be used so that the screen
ground connection from the insert points on the console provide a reference for all
signals within the inserted unit, eliminating the possibility for induced noise to corrupt
the signal path. Two-core cables should be used with one core carrying the signal and
the other carrying the ground plus an overall screen (also grounded). The screen can
be connected at both ends or, as with balanced systems, it can be broken at one end if
that improves performance. Some experimentation may be needed.
Ground lift connection on destination
Ground lift connection on source
Chassis
Chassis
Earth lift
switch
Source
Destination
Screen
Chassis
Chassis
Earth lift
switch
Source
Destination
Screen