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发表于 2004-2-2 00:48:21
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a closer look : : .
Ever since the introduction of the NAD Silver Series, the S 500 CD Player
has had a strong following due to it's perfect balance of superb perfor-mance
and affordable price. All the expertise and knowledge which has
been build up over nearly 20 years of designing and manufacturing
award winning CD Players comes together in what might arguably be the
best NAD CD player yet: the new NAD Model S 500i.
Features
Although primarily intended for professional products, balanced in- and
outputs are becoming a more regular feature on high quality audio
equipment as the advantages are numerous: far less interference, rela-tively
insensitive to cables even with long stretches. Besides the conven-tional,
unbalanced RCA output the Model S 500i also sports a set of truly
balanced XLR outputs so it can easily be combined with professional
components or the very best Hi-Fi components that also offer balanced
XLR inputs. Digital data transfer is becoming ever more important and
so apart from the normal coaxial digital output, a true professional digi-tal
output (conforming to the AES/EBU standard) is also provided. Not
all digital outputs are equal: In the case of the NAD Model S 500i the
outputs are buffered and isolated by a transformer from the converter
itself and the output impedance has been carefully tailored to produce a
precise 75 ohm impedance. This ensures perfect matching for the low-est
possible digital jitter performance. With the use of correct cables,
effects such as reflections, overshoot and spurious signals will be elimi-nated
from either of the Model S 500i's digital outputs. In true NAD tra-dition,
the NAD Model S 500i is extremely easy and straightforward to
operate. The provided remote control will allow you to operate the Model
S 500i from your preferred listening position and using the NAD Link
connectors you can operate a complete NAD system.
Design
Audiophiles know that "Class A" operation is arguably the best approach
to achieve -both measured and subjectively- the highest level of perfor-mance.
The analogue stages for the Model S 500i are biased for pure
Class A operation from input to output stages. To provide perfect low fre-quency
behaviour the Model S 500i is true DC coupled. Although the cir-cuit
topology is inherently stable under all operating conditions, there is
still the DC servo circuitry present as an extra precaution. This circuitry
has been included to deal with the large number of discs, which have
inherent DC offset, due to errors during the mastering process in the
production of the disc. As with all quality audio components, a healthy
power supply is always a key element towards high performance. For the
Model S 500i a specially designed toroidal transformer is used with low
magnetic radiation, partnered with low impedance and low ESR capaci-tors.
The power supplies for digital and analogue sections operate from
separate transformer secondaries. On top of that, each section in the
Model S 500i, such as digital, logic, servo, and amplifier stages, have
their own separate power regulators to ensure total freedom from noise,
hum, interference, and other electrical artifacts. For the S 500i a Crystal
Digital-to-Analogue converter chip with 24-bit resolution was chosen for
its excellent low level linearity, low distortion and low noise. A specially
designed 384 times over sampling digital filter is employed to extract the
maximum performance from the DAC. Instead of using a 4-pole filter in
the analogue stage, as is the norm with most CD players, a 5-pole filter is
used, removing spurious RF interference more effectively and reducing
group delay while keeping the audio band totally clean. The meticulously
designed double-sided, high grade glass fibre PCB design with its star
grounding and the use of selected and close tolerance components fur-ther
reduces any chance of RF contamination. In fact, the distortion level
and signal-to-noise ratios for the Model S 500i are very close to the theo-retical
limit of the DAC itself. The slim line transport mechanism chosen
uses a brushless motor (Hall effect) which helps keeping jitter to a mini-mum.
The 3-beam laser assembly assures accurate tracking of even
damaged discs.
The Listening Experience
As always, sonic performance is the first priority at NAD. The S 500i is
designed to stand as the primary source in even the most demanding of
systems. Tremendous bass dynamics are combined with an expressive
mid band and punctuated with a sweet and delicate treble. Subtle
details are faithfully retrieved from even the most densely scored musi-cal
works, bringing out the texture and nuance of musical expression.
Instruments emerge from a velvety black quiet into a palpable three-dimensional
sound stage. Each instrument retains its individual charac-ter
and is firmly planted in space. Music flows with the ease and preci-sion
that makes recordings come to life, and makes listening to them a
true pleasure. The S 500i can stand proudly in that very small group of
electronic instruments that can be regarded as reference class.
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