Accuphase DP-55-V Brochure

m MDS type D/A converter achieves 24-bit linearity and minimizes noise
m Two sets of digital inputs and outputs m High-performance digital

demodulator with minimum jitter m 3-pole analog filter with hand-selected
components m Fully digital control of CD mechanism m Balanced actuator
drive circuitry

First-rate CD player built for no-compromise sound. Independent processor
section features revolutionary MDS (Multiple Delta Sigma) converter with
24-bit ultra high precision. Full array of coaxial and optical inputs and outputs.
Digital control of CD transport mechanism allows instantaneous optimizing
of servo operation. Noise-free analog output with totally balanced
configuration.

The DP-55V is a further refined version of the
model DP-55 coveted by audio connoisseurs
the world over. It incorporates the latest
advances in digital technology, allowing it to
deliver superb Compact Disc sound.
Independent use of the digital processor is also
possible, providing excellent cost-performance
ratio.
The processor features a revolutionary MDS
(Multiple Delta Sigma) converter with superb 24­bit precision. This ensures ultra low distortion
and outstanding signal-to-noise ratio. A set of
digital inputs (coaxial and optical) lets external
digital sources also gain access to this superb
D/A converter, for
playback with opti­mum sound qual­ity. The DP-55V
even provides digi­tal outputs (coaxial

Optical input display example

and optical), allow­ing connection of
digital recorders
such as CD-R,
DAT or MD units.
This lets you make

Optical input display example

direct digital recordings of supreme quality, us­ing the signal from the internal CD transport or
from an external source.
The CD transport section uses fully digital
circuitry for control of all actuators and
mechanical functions. This enables instant
optimization of servo parameters for each
individual disc as it is being played, resulting in
stable operation and a drastic reduction of
readout errors. The laser pickup is an ultra­compact type with integrated RF amplifier, and
all actuators are driven by balanced circuits
where no current flows in the ground line. A tray
lock feature firmly secures the tray during
playback, and the entire CD mechanism is
mounted on a metal chassis of high rigidity,
designed to minimize any vibrations that may
arise during playback. In this way, the DP-55V
covers every electrical as well as mechanical
aspect to assure highly precise readout of the
digital signal. A digital level control and balanced
output circuitry are further advantages for
optimum sound.

Digital Processor Section

Innovative MDS (Multiple Delta Sigma)
converter reduces distortion to theoretical
limits and assures outstanding S/N ratio

The D/A converter which generates the output
signal is a newly developed type that provides
excellent performance in terms of performance
and sound quality. The
MDS (Multiple Delta
Sigma) principle em­ploys several delta
sigma type converters
in a parallel configura­tion which results in a

drastic precision enhancement. The delta sigma
principle combines oversampling with noise­shaping (a kind of digital feedback) which
projects the amplitude information of the digital
signal onto a time axis for precise conversion.
Figure 1 shows several delta sigma converters
which are fed with the same signal and whose

Signal

Conversion error

Digital
input

Note the ratio between signal and
conversion error. In the MDS output,
the error is very small in relation to
the signal.

Fig. 1 MDS type D/A converter principle

MDS
output

outputs are combined to arrive at the overall
waveform.
In the DP-55V, two delta sigma converters are
operated in parallel, which results in a
performance improvement by a factor of 1.4
(=√2). An important characteristic of the MDS
principle is that the performance benefits are
achieved regardless of signal frequency and
signal level. Therefore noise at very low signal
levels that was difficult to contain with
conventional delta sigma converters is now

Analog output
[dB]

Linearity (digital input vs. analog output)

LINEARITY

[dB]

Digital input

drastically reduced. The audible result is music
reproduction emerging from utter silence with
an impressive sense of clarity and nuance.

Separate processor section with coaxial and
optical input for digital signals

Digital inputs allow the user to enjoy the top­level performance of the
processor section also
with other components
that can supply a digital
signal, such as another
CD transport or a DAT or
MD player. For utmost
flexibility, the input can

Digital inputs

handle both optical and coaxial connections.
Internal processing of audio data is carried out
entirely in 24-bit format.

Two digital outputs allow direct digital
recording

The DP-55V provides a coaxial and an optical
output connector which allows direct connec­tion to the Digital Pream­plifier DC-330, or to a
digital recorder such as
a DAT, MD, or CD-R unit.
The outputs carry not
only the signal from the
internal CD transport, but
also from components
connected to the digital

Digital outputs

input, allowing direct digital recording with un­precedented flexibility.

Jitter-free high-performance digital
demodulator

Demodulation of the digital signal is carried out
by a CS8412 chip (made by Crystal
Semiconductor). This device not only has
extremely low inherent jitter, it also is capable
of absorbing any jitter components contained
the input signal. Since the chip can handle digital
signals up to a width of 24 bits, the advantages
of the MDS principle can be realized with any
type of program source.

Linear phase analog filters provide superior
phase characteristics

The frequency upper range of the D/A converter
output signal by principle contains noise
components. The analog filter serves to remove
such aliasing noise. The filter in the DP-55V is a
3-pole linear phase type filter with outstanding
phase characteristics. The cutoff frequency is
designed to minimize phase shift within the
passband. Strict selection of all filter components
assures sonic purity and total musical accuracy.

Digital level control prevents sound quality
deterioration

The 24-bit MDS D/A converter in the DP-55V
has an 8-bit margin, which allows precise level
attenuation down to -40 dB without any loss in
signal quality.

Fully balanced analog output circuitry

The audio output section features completely
balanced circuitry which is isolated from the
ground line. Any noise that may be induced in