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14
Grounding Techniques
Hum and buzz are the biggest enemies you face when interconnecting a large number of
different pieces of equipment to one another. This is because each piece of equipment
may operate at a marginally different voltage (this difference is called potential) and, when
two devices at slightly different potential are physically connected with audio cabling, the
end result can be nasty, extraneous noise (mind you, connecting two devices at very
different potential can result in a major electrical shock!).
However, there are several steps you can take to avoid grounding problems. First,
assuming you have an isolated electrical circuit that can handle the electrical demands of
all connected audio equipment (these needs will usually be modest), you should always
plug all connected equipment into the same circuit. If possible, nothing else but this
equipment should be connected to that circuit. If you can’t do this, at least avoid plugging
your audio equipment into the same circuit that is already powering things like heavy
machinery, air conditioners, heaters, refrigerators, washing machines, neon signs or
fluorescent light fixtures. One particular culprit that will almost certainly create problems is
the standard light dimmer (the kind that uses silicon controlled rectifiers). Where low-level
lighting is desired, use incandescent fixtures with autotransformer-type dimmers
(sometimes called Variacs) instead—these cost considerably more than the standard
dimmer you’ll find at your local hardware store, but are well worth the extra expense.
Three-prong plugs (such as the one used by the E62i, E31i and E30i) should always be
used as is; don’t use adapters. If you are using rack-mounted audio devices such as the
E62i, E31i or E30i and are experiencing hum or buzz, there's a simple test to determine the
source of the problem: while keeping all devices powered on and connected with audio
cabling, physically remove each device, one by one, from the rack. If the hum disappears
when a particular device is removed, that device is the culprit.
We also recommend that you use balanced audio cabling and connectors wherever
possible. All three models provide electronically balanced inputs and outputs. The
diagram below shows how XLR connectors should be wired for use with these inputs and
outputs.
In addition, you can minimize possible interference by planning your audio, electrical, and
computer cable runs so that they are as far apart from one another as possible and so they
don’t run parallel to one another. If they have to cross, try to ensure that they do so at a
90° angle (that is, perpendicular to one another). In particular, try to keep audio cabling
away from external AC/DC adapters.
If you’re using the E62i, E31i or E30i in a fixed location such as a recording studio, you
may want to invest the time and money into creating a star ground network. This is by far
the best technique for avoiding grounding problems. It involves using a formidable ground
source such as a cold water pipe or a copper spike driven into the earth. A thick grounding
cable is connected to that source and is then brought to a central distribution point; from
1 GROUND
3 COLD (-)
2 HOT (+)
+
ENGLISH