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is more efficient than conventional linear power regulators. This principle
allows easier control over the power dissipation but it produces high-
level interferences at the switching frequency of the regulator, which is
in the range between 40 kHz and 100 kHz with most devices. Since the
switching regulator does not produce clean sine waves, many additional
harmonics are produced as well. There are several different types of
switch mode regulators that produce different sorts of interferences, but
for our problem, this is not important. What is important is that every
device has a built in RF filter whose job it is to avoid the disturbance of
the power line. Of course, the protective connector is used to leak the
RF interference. This adds a considerable amount of RF current into any
ground system that can cause many strange problems. While a 50 or 60
Hz voltage offset on the ground system will be different in several parts
of an audio system in the same room if all the units are ground connected
using appropriate cross section lines, the RF signal can spread out much
easier. The voltage drop depends not only on the real resistance of the
ground connections but also on the inductive reactance of the wires that
is proportional to the frequency. It is almost impossible to make realistic
calculations. The only remedy is to increase the cross section of the
ground cables that ground all parts of the audio system. The higher the
cross section is the 'closer' is each device to ground and the lower is the
probability that RF signals are injected into the ground system.
Neutral connector
In some countries, it is common to connect both the protective conductor
and the neutral conductor in the power distribution panel. As far as safety
considerations are concerned this works fine, as far as audio grounding is
concerned, this method spoils the entire system described above. If there
is a connection between the neutral conductor and the separate ground
line, the ground line is ineffective, because it is just a parallel line to the
neutral connector. Please, make sure that this is not the case with your
installation.
Let's put this together:
The base of a problem free installation of the entire studio system
is a solid, high cross section ground that is directly connected to
a low impedance ground node, which is in most cases the mains
power entry in the basement of a building. This main audio ground
should be used to connect the electric ground and protective
ground of all devices in the studio with high cross section cable.
Care must be taken that the ground connector is isolated from the
neutral conductor.
ONLY QUALIFIED PERSONNEL IS ALLOWED TO INSTALL
OR MODIFY ANY ELECTRICAL SYSTEM. MISTAKES AND/OR
NEGLIGENCE CAN CREATE LIFE THREATNING SAFETY HAZZARDS.
UNDER NO CIRCUMSTANCE SHOULD UNQUALIFIED PERSONNEL
TOUCH THESE CIRCUITS
LIFE IS IN DANGER IF SAFETY RULES ARE NOT FOLLOWED.
Assignment of phases
The assignment of the three phases of the mains power line should be
carefully distributed to the different sorts of equipment in the studio. If
this is left to chance, it is likely that you have to deal with many avoidable
problems. There is one basic rule. Put all audio equipment on one phase
and DON'T install any household appliances to this phase. Mark all wall
outlets of the 'audio phase' carefully and take care that there are enough
additional wall outlets that are connected to another phase. Of course,
these outlets should also be marked. If you don't do so, you might have to
deal with click noise, strange problems with noise or strange behavior of
some systems every once in while. In a complex system, it is very difficult
to figure out what the reason for a particular problem like this really is.
Household appliances with temperature controls, switched power supply
and ineffective filters, thermostats, relays and other components can
cause this.
The 'one phase for audio principle' offers another advantage. If you
have to deal with a mains supply that is already 'dirty', since there are
companies in the neighborhood that have huge power consumption and
produce interference, you can single out the best phase for audio, just by
rearranging the phases in your distribution panel –
AND AGAIN, THIS MUST BE DONE BY A QUALIFIED ELECTRICIAN
AND IN ACCORDANCE WITH ALL SAFETY REGULATIONS IN YOUR
LOCAL AREA.
SRC
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