Avoiding Ground Loop Noise - Alesis Ineko Reference Manual

Avoiding ground loop noise

In today's studio, there are many opportunities for ground loop
problems to occur. These show up as hums, buzzes or sometimes
radio reception and can occur if a piece of equipment "sees" two
or more different paths to ground. While there are methods to
virtually eliminate ground loops and stray radio frequency
interference, most of the professional methods are expensive and
involve installing a separate power source just for the sound
system. Alternatively, here are some helpful hints that
professional studio installers use to keep those stray hums and
buzzes to a minimum.
KEEP ALL ELECTRONICS OF THE SOUND SYSTEM ON THE
SAME AC ELECTRICAL CIRCUIT.
Most stray hums and buzzes happen as a result of different parts
of the sound system being plugged into outlets of different AC
circuits. If any noise generating devices such as air conditioners,
refrigerators, neon lights, etc., are already plugged into one of
these circuits, you then have a perfect condition for stray buzzes.
Since most electronic devices of a sound system don't require a
lot of current (except for power amplifiers), it's usually safe to
run a multi-outlet box or two from a SINGLE wall outlet and
plug in all of the components of your system there.
KEEP AUDIO WIRING AS FAR AWAY FROM AC WIRING
AS POSSIBLE.
Many hums come from audio cabling being too near AC wiring.
If a hum occurs, try moving the audio wiring around to see if the
hum ceases or diminishes. If it's not possible to separate the
audio and AC wiring in some instances, make sure that the
audio wires don't run parallel to any AC wire (they should only
cross at right angles, if possible).
TO ELIMINATE HUM IF THE ABOVE HAS FAILED:
A) Disconnect the power from all outboard devices and tape
machines except for the Ineko, the mixer and control room
monitor power amp.
B) Plug in each tape machine and outboard effects device one at
a time. If possible, flip the polarity of the plug of each device
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Ineko Reference Manual