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Leaving the analog/digital division far behind - this digital preamplifier
features ultra high-speed DSP and complete readiness for the new
generation of super high quality audio sources. The newly developed
MDS (Multiple Delta Sigma) converter with 24-bit ultra high precision
resolution results in dramatically enhanced performance. Witness a new
dimension of audio perfection.
The DC-330 builds on the foundation of the
DC-300, with some significant advantages over
its predecessor. Ease of use has been fur ther
enhanced, and latest digital technology and
redesigned circuitry assure total compatibility
with the emerging new generation of top-quality
audio sources such as SACD and DVD-Audio.
The digital volume and tone controls function
with previously unattainable precision, yet their
smooth operation feel is on a par with the best
of analog equipment. Internally, the DC-330
features ultra high-speed digital processing
performed by a latest-generation DSP device.
D/A conversion is handled by an innovative MDS
(Multiple Delta Sigma) converter which boasts
superior accuracy. This makes the DC-330
capable of bringing out the full potential of a
new breed of audio sources that is just
emerging, such as the Super Audio CD (SACD)
and DVD-Audio. During the development of this
amplifier, countless listening sessions were held
to arrive at the detailed, rich sound that is a
hallmark of every Accuphase product.
In a preamplifier, the part that has a decisive
influence on the sonic end result is the section
where adjustments such as volume, tone, and
loudness compensation are carried out. In the
digital DC-330, this task is handled by an
extremely fast DSP that assures a drastic leap
in performance, achieving outstanding
signal-to-noise ratio, amazing channel
separation, and totally negligible distortion. The
overall result is utterly natural and realistic sound
with full control over every vital aspect.
To provide complete flexibility with a view to
future expansion, all inputs and recordingoutputs of the DC-330 are implemented as
option boards. The option board slots suppor t
the ADB2 (Accuphase Digital Bus 2) interface
which accommodates also formats such as
SACD and DVD-Audio. The DC-330 comes with
a line input board for analog signals and a digital
input/output board installed as standard
equipment.
As a perfect blend of analog operation feeling
and sophisticated digital technology, the DC-330
transcends the mechanistic division of -analog-
or -digital-, fusing them both into a higher
dimension that is devoted solely to the
enjoyment of music.
Fully digital preamplifier with ultra
high-speed DSP and support for high
sampling rates: 2.8224 MHz/1-bit and 192
kHz/24-bit.
Figure 1 shows the block diagram of the DC-330.
Digital sources are connected via coaxial or
optical inputs located on option boards. All
option board slots of the unit are ready to handle
the bit stream output of a SACD player which
uses 2.8224 MHz/1-bit,
as well as the 192 kHz/
24-bit signal used for
DVD-Audio. Other
high-quality formats that may emerge will also
pose no problem to the DC-330. After the input,
an ultra jitter-free PLL
circuit extracts a
high-precision
reference signal totally
free from the adverseeffects of pulse transmission distortion and jitter.
After conversion into the internal format of the
DC-330, a DSP (Digital Signal Processor)
operating at extremely high speed performs
some of the
major tasks that
are handled by a
preamplifier,
such as tone
control, loudness
compensation,
as well as mono
and phase
switching. All of
these adjustments are accomplished entirely in
the digital domain.
An ultra high-speed -isolated digital coupler-
ensures effective electrical separation between
the digital section encompassing the DSP and
the D/A converter and subsequent analog
segments of the amplifier. After digital volume,
balance, and attenuation processing, the signal
reaches the newly developed MDS type D/A
converter which produces an analog signal of
utmost precision. A 3-pole linear phase low-pass
filter then removes any remnants of the digital
process, before sending the signal to the
balanced and unbalanced outputs.
Innovative MDS (Multiple Delta Sigma)
converter reduces distortion to theoretical
limits and assures outstanding S/N ratio
The D/A converter which has considerable
bearing on the sonic end result is a newly
developed type that provides
excellent performance in all aspects.
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 noise-shaping (a
kind of digital feedback) which
projects the amplitude information of
the digital signal onto a time axis for
precise conversion. Figure 2 shows
several delta sigma converters which
are fed with the same signal and
whose outputs are combined to arrive
at the overall waveform. In the
DC-330, six delta sigma converters
are operated
in parallel,
which results
in a perfor-
mance
improvement
by a factor of
2.45 (=Ö6). An impor tant
characteristic of the MDS principle
is that the performance benefits are
achieved regardless of signal
Fig. 1 DC-330 block diagram
Ultra high-speed DSP
Unbalanced
Outputs
Left
Analog
Outputs
1
2
Balanced
Outputs 3-Pole
Linear
Phase
Low PassFilter
Balanced
Buffer1
2
Option
Slot 8
Analog Input
AI2-U1
Option
Slot 7
Digital
Input/Output
DIO-OC1
Option
Slot 6
Option
Slot 1
Coax
RX
Opto
RX 24-bit A/D
Converter
Opto
RX
Opto
RXCoax
CoaxMaster
Clock DAI
Decoder
DAI
Encoder
Ultra
Jitter-Free
PLL
Tone
MonoComp
Phase Volume
Balance
Attenuator
Digital
Isolator MDS 24-bit
D/A Conver ter ×6
Opto
RX
Coax
RX
External
DSP
Option
(
DIO-OC1)
Volume
Control
Outputs
Option
(
DIO-OC1)
VolumeVolume
Information
Digital Filter
Volume
Balance
Attenuator
MDS 24-bit
D/A Conver ter ×6
Left
Right
Digital
Isolator
Unbalanced
Outputs
Right
Analog
Outputs
1
2
Balanced
Outputs 3-Pole
Linear
Phase
Low PassFilter
Balanced
Buffer1
2
DSP
Digital Filter
DS
DS
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frequency and signal level. Therefore
noise at very low signal levels that was
difficult to contain with conventional delta
sigma converters now could be drastically
reduced. The audible result is music
reproduction emerging from utter silence with
an impressive sense of clarity and nuance.
Volume control with smooth analog feel
A massive knob on a precision-machined shaft
rotates a disc with star-shaped slits which
Fig. 2 MDS type D/A converter principle
generate a series of pulses in
a phase detector. These
pulses are utilized by a
microprocessor to govern the
volume control function. For the user,
the volume control of the DC-330 operates
with a silky smooth and natural feel that perfectly
matches the audible change in volume. The
current volume setting is indicated by the
numeric display and also by an array of LEDs
on the circumference of the control. This lets
you check the setting at a glance.
Linear phase analog filters provide superior
characteristics
The analog filter, which serves to remove
aliasing noise in the extreme upper frequency
range, is a 3-pole linear phase type filter with
outstanding phase characteristics. The cutoff
frequency is optimized to minimize phase shift
within the passband. Strict selection of all filter
components assures sonic purity and total
musical accuracy.
D/A converter with printed circuit boards
made from Teflon (glass fluorocarbon resin)
with low dielectric constant and low loss
The D/A converter boards use a substrate of
nThis photograph shows the DC-330
with separately available option boards
installed and with the shielding cover
removed.
nPCB assembly with analog
output connectors (balanced
and unbalanced, 2 each) and
MDS D/A converter (2 boards
for left and right) using Teflon*
(glass fluorocarbon resin)
substrate with low dielectric
constant and low loss.
nSupplied remote commander
RC-24
Allows input selection and
adjustment of volume, tone
control on/off, loudness com-
pensator on/off, attenuator
on/off, and other functions.
glass fluorocarbon resin which has a stable, low
dielectric constant as well as superior heat
resistance and high-frequency characteristics.
Using this material for the audio circuitry assures
signal transmission with utmost purity, resulting
in a clear improvement in perceived signal-
to-noise ratio. In the DC-330, gold-plated copper
DAC
#1
#2 S 1 e1 S2
e2
Sn-1
en-1
S0
e0
Sn
en
#1
#
n
MDS
output Digital
inputSignal
Conversion error
