Accuphase DC 300 Brochure

Page 1

PRECISION DIGITAL PREAMPLIFIER

. Fuiry nigllal SignaJ chessing Prunipifial. Dlg'llnl Laval Atlanualm mm Advanced Noise
Shaping Tecnnology OVolume Conlrol Provides Smualh Analog Fuel 0 MME Typa pm Can-
Venn! Achieves 20m Linearity and Mlnlmum Noise 0 man Jinn-rm PLL simuil 0 High-
Pmcisinn Sampling Frequeflcy Convenw. asp Tune Control Allows Precise Adluslmenl Wilh-
oul Sound analily Degmdalinn .Versllilu Array nl Dlglial and Analog lnpui/oulpul cpllons

pig/M

Page 2

Ever since the advent of the Compact Disc, the shift
from analog to digital has been gaining momentum
in the audio world. Practically all program sources
introduced in recent years, such as MiniDisc. DAT.
and even satellite broadcasts are digital. When the
source is digital. it is of course desirable that the
reproduction system also be capable of handling
the signal in the digital domain as far as possible.
because this will assure that the signal quality re-
mains at a high |eve|.This especially is true in areas
where the frequency spectrum is being altered. such
as in tone control and filtering stages. Use of a digi»
tal design will assure much higher precision and
sonic fidelity than analog circuitry can provide.

Looking towards the fast-approaching 215t century.
Accuphase has harnessed its extensive expertise
in digital technology for a new product that makes
full use of advanced. highvspeed digital signal pro-
cessing power. By introducing the first fully digital
preamplifier. Accuphase is again opening up new
vistas that show the shape of things to come. From
the outside. the 00-300 is deceptively similar to
earlier high-class preamplifiers from Accuphase. But
on the inside. its a whole new story Volume con<
trol. balance control. tone control, and loudness
compensation are all achieved by sophisticated DSP
technology. using a 48-bit wide data path. Only im-
mediately before the output. a high~performance
MMB type D/A converter turns the signal into ana-
log form. Smoothness and ease of use are on a par
with the best of Accuphase's analog components.
while signal quality and performance

Fully digital preamplifier opens up a new dimension in sound. Sophisticated noise
shaping technology allows ideal digital volume control. Super-precise MMB type
D/A converter, ultra jitter-free PLL circuit, and high-precision sampling frequency
converter further contribute to superb performance. Tone control with advanced
DSP adjusts timbre and allows loudness compensation without sound quality deg-
radation. Versatile array of option boards for digital and analog input/output.

precision signals before clock extraction. The re-
sulting signal is then processed by the DSP (Digi-
tal Signal Processor) performing all preamplifier
tunctions such as tone control. loudness compen-
sation. stereo/mono switching, phase switching,
etc. All of these func~
tions are handled in the
digital domain. so that
no signal quality degra-
dation can occur.

After being routed
through the digital filter ultra-high-spsed DSP chip
with S-times oversampling. the signal enters the
next stage with separate high-speed DSP chips
for each channel. Here, digital gain control is per-
formed using a revolutionary principle developed
by Accuphase. Special noise-shaping technology
allows attenuation down to ~95 dB with minimum
quality degradation. This stage also performs bal-
ance adjustment and attenuation switching.

Finally, the signal passes through ultra high-speed
optocouplers which assure perfect electrical sepa-
ration ot digital and analog sections. The D/A con-
verter section makes full use of the MMB (Multiple
Multi-Bit) principle to achieve outstanding conver»
sion precision. A 4-pole analog filter reliably re-
moves all digital remnants. and the resulting
ultra-pure analog signal is then output via balanced
and unbalanced circuits.

Digital Volume Control With Special Noise
Shaper Technology

An important task of any preamplifier is volume
adjustment. a function which has a great bearing
on sound quality. By employing a newly developed
noise shaping principle for digital level control.
Accuphase has made it possible to realize a fully
digital. high-quality preamplifier.

When a conventional D/A converter is used for level
control. digital noise increases at higher attenua-
tion settings. leading to a pronounced downgrad-
ing of signal quality. The Accuphase noise shaper
on the other hand. made possible by high-speed
DSP technology. reduces noise within the audible
f r e q u e n c y
band to the ab-
solute theoreti-
cal minimum. , ~v WW ----- ~
Thanks *9 919'- L ..| ..| .l. .l .L ll l.. lull
tal tlme lelslon "° :2 .. .. u .t m u. ask
feedback. even Noisoshapsrofl
extremely low-
level data will
not be buried in
noise. achiev-
i n g a rn u c h
higher resolu»
tion than pos-
sible with the
conventional

Noise shaperon

Fig. 2 Frequency spectrum

(Dunn playback of 2 kHz tone at
an a . with volume selling -20 as)

have been further improved thanks to
the all-digital principle. The DC-SOO wtll
lead the listener into a new realm of
sonic enjoyment. Far beyond the ana-
log versus digital debate. it reproduces
music with spatiality and transparency
that simply is in a class of its own.

System Features

Figure 1 shows a block diagram of the
DC-SDO. An array of coaxial and opti-
cal inputs accepts digital signals of up
to 24 ~ bit resolution, with a sampling
frequency of 32. 44.1 or 48 kHz. The
DAI (Digital Audio Interface) decoder
automatically locks to the sampling
frequency. Input signals with a sam-
pling frequency of 441 or 48 kHz and
level I precision are supplied directly
to the Ultra Jitter-Free PLL Circuit
which extracts a master clock signal
that is entirely devoid of pulse distor»
tion and jitter. All other input signals
are first routed through the SFC (Sam-
pling Frequency Converter) which

Unbalanced
L chlnnol (mm

Fig.1 Block diagram of DC-300

Alh o
LPF
Ell-hold
Output-

Unbllnncld
R channel on u
l
Atn Order
LFF 2
Dumms

Q l
53W @
2

turns them into 48 kHZ. level | high-

Page 4

l.
(Option model names given In brackets.)
.Digitél: ,r , ,
a Accepts digital output signals lrorn CD transports, digital
recordersMD and DAT
. ocrsuo main unit provides two coaxial and two Toslinir
optical inputs
ii Option boards can be mounted in the rear-panel slots for
BNC(D|»BNC1l, HPC optical cable (DI-5T1), and HPC
balanced cable lDlO-FROi)

, we; We: ,

MD, etc.)

w Optional digital input/output board iDlo-ocri provides
connectors for two additional digital recorders

r Optional AES/EEU standard digital input/output board
(DIO-PROt)

- Dedicated src provides AAA/ea kHz sampling trequency
conversion for recording

Arialé'gtl ill: to ,.
~ Supplied as standard equipment, a line input board
(A|~Ul) accepts all analog line-level inputs lrorn CD
players, tuners, analog tape recorders, laser disc line-level
audio output and the analog output ol DAT and MD players
.i Additional unbalanced (Al-U1) or balanced lAl-Btl input
boards possible

e eaves m; (we a

,Bhonoiplaybac . ,

. Optional analog disc input board lAl»ADi) allows playback
or analog records

.. To provide separate inputs lor MM and MC, two analog
disk boards can be installed

Analoglrecordingi' '. , 'i #4»

w Optional line input/output board lAlO-Ut) allows record-
ing and playback with analog tape recorder or analog
connection of DAT, MD or similar

~ Optional unbalanced (AO-Ui) or balanced (AO-Btl output
boards provide dedicated high-quality signal lor analog
recording

Di] '7"in , . .
. Digital-to»digltal copying possible
- Digital-to»analog and analog-to»dlgital (AIO»U1I copying

possible
- independent Fiec Out selector allows recording and dub-

bing while listening to a different source

IEXATDSPicb'fnhéiz-itorsr. '-l ' "i " 7
a Digital I/O connectors allow connection of external dlgital
graphic equalizer

, 9363f .
.i Two sets ol unbalanced and balanced output connectors
ior power amplifier connection

The I ustratlon shows a connection example WI h option boads installed.

Option borad installation example [from left)

Line input board (AIVU1) (standard equipment)
Analog disc input board (AI-Am)

HPC optical input board (DIVST1) O t'
Line input/output board (AID 1) P °"
Line output board (AO-Ut)

For connection to digital eoulpment,you can use 757mm coaxlal cable. Toslink optical riber
cabie, HPC optical liper cable or similar,

For analog input/output connectionsuse audio cable equipped with pnono plugs, and take
care not to mix up iert and right cnanneis.

CD transport or other digital

source component

Tuner, CD player or other
component with analog output

eicrm our

HPc col-cal libel cabfe

75c martial cable

lINE lN

For analog
recording only

point
our

Tape recorder or other analog
recording/playback component

DIGlTAL our

rosirnir optical libel cable

DAT, MD, etc,

Digital graphic equalizer

DAT, MD, etc.

DlElTAL our claim lN

claim lN

750 coaxial cable

759 coaxial cable

@959

Audio cable wnn plug

Balanced cable r
r
r
i

Power amp

,/
'11;

I
12%;

Speaker systems

Ultra Jitter-Free PLL Circuit

For the purpose of synchronizing operation of the
D/A converter with the digital audio interface (DAI),
a phase-locked loop (PLL) circuit is used which
generates a master clock to be used as a system
reference. As shown in the diagram. the Ultra Jit-
ter-Free PLL Circuit of the DC-3OO consists of a
preamble detector and a voltage-controlled 05-

MIL

m. .w innit Em,

Promot- owl
trail- mum mitt-moi

mu Leah
M lilur

premium-rem»

Ultra Jitter-Free PLL Circuit

cillator (VCO) using a quartz crystal element. The
master clock produced by this PLL circuit is totally
free from the effects of pulse distortion and jitter,

High-Precision Sampling Frequency Converter
A sampling frequency conv
verter (SFC) is available to
transform the sampling fre-
quency of digital input sig-
nals to the desired value. In
the 00-300, the sampling
frequency is arithmetically

High-precision ch
converted to a higher value (up-conversion) and then
to the 48 kHz level | signal. The highly precise quartz
oscillator used for this conversion assures flawless
and virtually jitter-free performance.

ZO-Bit, B-Times Oversampling Digital Filter
Moving unwanted sampling frequency remnants
(also called aliasing components) far outside the au-

dible range is the task of an oversampling digital
filterl The NPC (Nihon Precision Circuit) digital fi|~
ter in the 00-300, cus~
tom manufactured for
Accuphase. offers
state-of-the-art charac-
teristics in all vital as-
pects, such as absence
of group delay, passband ripple, and attenuation,
approaching the theoretical performance limits.

20bit digital lilter

4-Pole Analog Filter With Hand-Selected Com-
ponents

To reduce noise in the upper frequency range and
achieve high S/N ratio, a 4-pole Butterworth de-
sign is used for analog filtering. The active iilter
allows optimizing of the cutoff point, to keep phase
shifts in the passband range at an absolute mini-
mum. Strict selection of all filter components as-
sures sonic purity and total musical accuracy.