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GENERAL TIPS
III
THE ELECTRICAL POWER SUPPLY OF AN AUDIO/VIDEO SYSTEM.
By
Jorge Knirsch
The
electrical supply and its wiring which feeds audio and video equipment
is the second most important factor (around 33% percent)
after acoustics, for the reproduction of sound. Reducing the garbage
from electrical energy, that is, from its harmonics (%THD) improves
listening and the soundstage.
©
2004-2008 Jorge Bruno Fritz Knirsch
All rights reserved
http://www.byknirsch.com.br
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The general universal rule
applies here as well : less is more, that is, in case of
doubt and lack of knowledge regarding what to do with electrical energy it's better not to do anything.
In other words, don't add anything to the power supply
network because the risk of increasing electrical energy's harmonic contents is
much greater than reducing it, without detailed knowledge about the
situation. Below we offer a practical guide in simple and efficient terms,
to be followed when optimizing electrical wiring.
● The use of dedicated and
exclusive wiring stemming from the installation's general mains supply
input box towards the audio and video equipment setup is
recommendable, for reducing harmonic contamination on the
audio/video system to be supplied.
●
Since breakers and fuses are
protection components used in series with the power main, those possessing
the least impedance, which are fuses, should be used in electrical feeding
applications for audio and video. Therefore, in all circuits
destined to audio and video we should prefer using fuses.
This is quite apt, mainly in studios. The reason for this is that
the breaker elements in fuses, normally called fuse links, possess smaller
impedance values than the sum of short-circuit coils and the breakers'
bimetallic resistances.
●
The dedicated wiring for
feeding equipment must use solid-core wires, also called
non-flexible, hard wires, for wiring phases and neutral, and flexible wiring
for grounding. Solid-core wiring, compared to flexible
wires of the same gauge, present greater increase in impedance values at high
frequencies due to the Skin effect. This
characteristic of solid-core wires helps reduce the flux of harmonics through
the power line.
●
The Electrical
contacts created by pressure of elements present
lower resistance values more than soldered contacts. Therefore, at the power line
electrical wiring joints, it's recommended to avoid solders possessing tin/lead.
●
It is important to
improve the grounding of the neutral at our power main,
because it is mainly a raised electrical network, and possesses
inadequate neutral pole grounding for this reason! Applying a grounding
shield to the installation's surfaces is more recommended in order to lower
neutral pole impedance, which adds to the electrical voltage stability and
drastically reduces noise.
●
Earth grounding
should be carried out as per the earth-earth grounding norm NBR5410 (in
Brazil), from
within the neutral pole grounding, so as to improve safety and
reduce noise. At the principle power mains box, mostly in studios, where the
neutral and earth poles lie, we may set up a system which allows changing an
earth-earth grounding to earth-neutral pole grounding, when the studio is
not being used, which aims to improve safety.
● We recommend that
transformers, line filters, voltage stabilizers, no-breaks and ferrite cores
around power cables be avoided, for they are the greatest culprits of harmonics in the power
main.
●
Whenever necessary, the
best thing to do is using just neutral and minimalist extenders,
avoiding line filters with components in series.
● Finally, for filtering,
the ideal thing is to use power conditioners possessing all inner
components in parallel with the power main.
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