Multimedia im Fahrzeug

Advice
The right cable-quality
a) The copper
he sound quality of a system depends very much on the kind of
Tcopper 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 which causes distortions. This oxygen-free
copper still contains 235 parts of oxygen within one meter.
The first quality level is (OFHC) copper. The method this wire is drawn
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.
On the basis of the former facts we were again able to improve the copper
our RCA-cable „LONDON“ is made of. By means of an extended sinter
process, the cable is drawn with greatest care as a long mono crystal.
The degree of purity ranges about 99,99997 % (UPOFC).
The usual impurities like iron, sulphur and parts of antimony, aluminium as
well as arsine have been reduced to an unimportant quantity. We again
managed to reduce the oxygen parts down to 19 parts/m. Acoustically the
advantages become at once obvious.
This wire is made of OFHC-copper with a pure silver-plated surface:
Double shielded RCA-cable „BERLIN“ (symmetrical construction)
A further wire made with OFHC-copper:
Double shielded RCA-cable „WOODSTOCK“
(symmetrical construction)
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 choice of loudspeaker-cables also benefits from this resolute
improvement the conductor has made:
Loudspeaker-cable „PROFESSIONAL LINE“ 4 sqmm
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.
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Our LS-cable „PROFESSIONAL LINE 2,75 sqmm“ is equipped with
cross-sections of the stranded wires with different diameters.The
largest diameter is placed in the centre of the cable. Low frequency signals
are only transmitted in the centre of the wire; for this reason the method
serves also as a sound tuning measure.
Due to the specific arrangement of larger stranded wire cross-sections
which are intended to improve the damping factor of the output stage,
a better impulse reproduction in the bass frequencies is achieved. The
higher the frequency is the more the signals belonging to the middle/high
frequency ranges are moving towards the surface of a cable. In this sector
we used smaller cross-sections so that the „skin-effect“ can’t be noticed.
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 short-circuited. 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. For our symmetrical RCA-cable „BERLIN“ we
preferred a parallel core layout. In addition, we covered the wire surface
with Teflon which is an acoustically neutral dielectric. As a result of this
excellent but expensive method we get a very low capacitive value and an
excellent holographic sound image. 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. Our symmetrical RCAcables
„WOODSTOCK“ and „NASHVILLE“ benefit of this twisted core
technique.
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.
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