Balanced Lines And Ground Lift Switches - Yamaha PM4000 Operating Manual

are required to implement this approach, since ground
is not carried between components. One drawback is
that cables may not all be the same – some having
shields carried through at both ends, and others not,
depending on the equipment – so it becomes more
complicated to sort out the cabling upon setup and
breakdown of a portable system.
Figure 4-10 illustrates a typical audio system in
which various grounding techniques are combined. The
basic rules that guide the choice of grounding schemes
may be sum-marized as:
1) Identity separate subsystems (or equipment envi-
ronments) that may be contained within an electro-
static shield which drains to earth.
Equipment Rack
Figure 4-10. Combining Grounding Techniques in a Practical System
2) Connect signal ground within each separate sub-
system to earth at one point only.
3) Provide maximum isolation in connections between
subsystems by using transformer coupled floating
balanced connections.
4.3.4 Balanced Lines and Ground Lift
Switches
By using balanced signal lines between two pieces of
sound equipment, you can lift (disconnect) the shield at
one end (usually at the output) of an audio cable and
thus eliminate the most likely path that carries ground
loop currents. In a balanced line, the shield does not
carry audio signals, but only serves to protect against
static and RFI, so you can disconnect the shield at one
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