Avoiding Noise; System Noise (Ground Loops, Hum, Induced Noise) - Alesis Studio 12R Reference Manual

Avoiding noise

If the Studio 12R is being run as suggested above, the noise of the mixer itself will not be a
significant factor in the noise level of your system, since the Studio 12R generates much
less noise than the typical source does. Noise is present in every system, analog or digital;
as operator it's your job to run the system (and particularly the mixer) so that the noise isn't
amplified unnecessarily. But the Studio 12R cannot remove noise that is already there. If a
low-level source with a poor signal-to-noise ratio is amplified by the TRIM and channel
fader, the noise will be amplified with the desired signal. A system is no quieter than its
noisiest component.
System noise (ground loops, hum, induced
noise)
In today's studio, with dozens of different pieces of equipment and
computers, 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, with one of the paths going down a signal
line. While there are methods that can virtually eliminate ground
loops and stray radio frequency interference, such as installing a
separate power source just for the sound system, most problems are
easier to solve. Here are some basic techniques that you should use
to keep stray hums and buzzes to a minimum.
KEEP ALL ELECTRONICS OF THE SOUND SYSTEM ON THE
SAME AC ELECTRICAL CIRCUIT. Most 60-cycle hums happen
because different components of a sound system are 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 as well. Since most electronic
devices of a sound system don't require very much power
(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 or the power transformers ("wall warts") used by
equipment requiring an external supply. 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, make sure that the audio wires don't run parallel to any
AC wire (they should only cross at right angles, if possible).
Studio 12R Reference Manual
Operating Instructions
35