Grounding Revisited
Next is a quick set of hints about where to look when trying to cure buzz troubles
in a recording studio. While the techniques are not meant to be taken as Gospel (some
techs might disagree with this treatise, so be it) these bits of knowledge were gleaned
from decades of experience in test equipment use, manual reading, facility design,
construction, trouble-shooting and being the chief of maintenance in some of the world’s
top studios, as well as problem solving in the home studios of rock stars and remote
recording/live sound situations. These hints have proven to work in many situations while
keeping systems safe and quiet.
While the usual scenario in hooking up equipment is that one plugs in the cables and
starts to work, the more complicated a system, the more likely it is that something will
not work correctly as far as hum and noise performance is concerned. While some would
blame the equipment, this is the equivalent of blaming the eggs for a bad soufflé. Usually,
hum and noise problems (and jitter or clock troubles in digital interfaces) can be traced to
poor planning and implementation of the studio’s
grounding situation
. It is illuminating
to realize that the engineers of yore in the recording, broadcast, and communications
industries have been through these troubles and figured out the solutions. History can
teach us a lot about how to avoid ground loops and their associated problems. The
manuals of many test instrument and recording equipment manufacturers from the ‘50’s
to the 80’s had chapters on how to fix hum and noise problems and it is from this wealth
of information that the writer draws ideas from for trouble free grounding schemes.
To comply with international standards and wiring practices, recording equipment
manufacturers are required to connect all the shield pins of audio and data connectors to
the chassis grounds of their gear. Sometimes, this can cause noise problems in large
systems where pieces of equipment are spread out around a facility because two
‘grounds’ are never quite at the same potential. This can cause ground loops (hums or
buzzing) if the cable shields are allowed to connect two chassis that are at different
potentials due to location, circuit wiring, or induction.
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