CANBusInterface

Advice
The right cable-quality
a) The copper
he sound quality of a system depends very much on the kind of cop-
Tper used for the wires. The cheap copper is available in many different
qualities. It is called „pure“ copper if there are about 4500 copper crystals
within one meter of a copper conductor (OFC). The current has to pass the
edges of the crystals whereas distortions may arise. Although, oxygen-free
copper still contains 235 parts of oxygen within one meter.
The first quality level is (OFHC) copper. The method of drawing this wire
reduces the number of oxygen parts down to about 40 oxygen-parts/m.
The lower number of oxygen parts reduces the oxidation between the
copper crystals. Furthermore, the material allows to quarter the number of
copper parts which also reduces distortion and background noises. The
sound delivered by an OHC cable is softer, cleaner with more dynamism
and transparency.
Furthermore, due to the silver-plated copper-wires the conductivity could
be improved and the oxidation within the conductor has been reduced. The
sound character gains in freshness and a more genuine impulse transmission.
Our loudspeaker-cables’ program also benefits from this resolute
improvement the conductor has made:
Loudspeaker-cable „Professional Line“
b) The „skin-effect“
he „skin-effect“ represents one of the greatest difficulties concerning
Tcables. The exact meaning of this term is often unknown. Most people
think that „skin-effect“ means a loss in power and they can’t believe that
it can take effect yet in the perceptible frequencies (20 – 20000 Hz)
because of the fact that the 3-db-point (half-division of power) of a cable
normally ranges at about 50 kHz.
In fact, the „skin-effect“ influences the values of resistance and inductivity
long before it causes a loss in power. As a consequence of these alterations
some frequencies come upon resistances whose sizes depend on
the respective distance to the surface of the conductor.
As a result of a too large cross-section (more than 2,5 sqmm) especially
the difficult high frequencies sound indistinctly. You can’t hear the details,
the sound is dump and flat, as if there were no harmonic waves.
The speaker cable „Professional Line“ offered by Dietz consists of wires
with different cross-sections. Low frequent signals are only transported
within the core. This is the reason why some of these cables are silver-
or tin-coated which avoids the oxydation of the wires and maintains or
improves their conductance. A positive side-effect resulting from this is that
the replacement of the high-frequency range to the silver coating improves
the damping factor of the output stage. The consequence is an increase of
the pulse reproduction in the bass range. There is no scope left for the
skin-effect to influence negatively the audio reproduction.
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c) Capacity and inductivity
nlike the power cables the current flow in the RCA- and Speakercables
Uis alternating. The capacity (like a capacitor) of a cable is determined
by the distance between the wires (positive or negative) as well as by the
electric properties of the dielectric material (insulation material). The better
the quality of the dielectric material is and the longer the distance between
the conductors is, the lower the capacity is getting. As far as the inductivity
(like a coil) is concerned it’s the other way round. The longer the
distance between the conductors is, the higher the inductivity is getting.
In case of a too high capacity, high frequent signals are shortcircuited.
In case of a too high inductivity, it opposes to the high frequent
signals a high internal resistance. Moreover, the length of a cable determines
the values of inductivity and capacity (the longer the higher). In
our „Silver Line“ cable the distance between the wires is larger to reduce
the capacity. In this case the inductivity doesn’t influence the sound
negatively.
Our 4-channel symmetrical RCA-cable „Munich“ is equipped with
4 insulated cores whose special layout enabled us to reduce the inductivity
decisively. The core layout can be parallel or twisted. Each variant
has got its own special advantages. It is true that capacity and inductivity
are slightly rising if the wire is twisted but their ratio is very advantageous.
But the most important advantage is a better suppression of induced interferences
mainly caused by the car electric system.
Even though the values of inductivity and capacity are not the most important
characteristics of a cable they are aimed to be kept small during the
development of a cable.This means practically that if the output
impedance of a control unit’s preamplifier output is more than 500 Ohm
and is connected with the amplifier by means of a long high capacity cable
of more than 1000pF the resistance in series and the parallel cable
capacity a kind of low bass. The result would be a lowering of the level in
the high-frequency range.