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MMB DIGITAL PROCESSOR
O MMB iype D/A converter achieves 20
ii linearity and super
low noise 0 Ultra Jiiier-iree PLL circuit. High precision sam-
piing irequency converierOVersaiile digiial input/output
Coniiguralion D MD REC switch allows recording from any
souvce. 4-pole analog filter with hand-seiected components
As we move towards the 21st century, digital program
sources such as CD, MD, DAT and others are occu-
pying center stage in the audio arena. These formats
are increasingly found not only in audiophile equip-
ment for home use but also in car stereo systems and
portable units as well. The 00-61 is a digital proces-
sor designed with this situation in mind. It
incorporates Accuphase-s extensive know-how in digi-
tal technology, allowing it to reproduce digital sources
with unsurpassed sound quality and to make optimum
use of the new generation of digital recorders.
The D/A converter section features the MMB prin-
ciple that guarantees conversion with ultra-high pre-
cision. Six hand-selected 20-bit D/A converters are
connected in parallel, resulting in a further increase
in all vital performance parameters. Thanks to
advanced techniques such as the Ultra Jitter-Free
PLL Circuit and High-Precision Sampling Frequency
Converter (SFC). pulse distortion and jitter are virtu-
ally absent, assuring absolutely faithful conversion
ot the input signal.
Connectors for digital recorders make it easy to hook
up for example a DAT deck or MiniDisc recorder. for
direct recording and playback of the digital signal,
An MD REC switch lets the user convert the sam-
pling frequency of the input signal to a high-preci-
sion 44.1 kHz level | signal for MD recording with
optimal quality. regardless of the type of input.
The digital/analog section employs ultra high-speed
optoisolators and digital couplers for perfect elec-
trical separation, thus preventing sound quality
degradation due to high-frequency noise and electri-
cal interference. The analog output circuitry employ-
ing fully balanced topology and a digital level control
are further advantages which assure sonic purity.
The elegant and refined design complements the
outstanding performance of the 00-61. This topÂ»
New-generation digital processor section with superb sound quality - MMB
type D/A converter featuring excellent conversion precision, ultra jitter-free PLL
circuit, high-precision sampling frequency converter and many other highlights
guarantee top performance. Versatile digital inputs can handle signals with all
three prevailing sampling frequencies, and two digital recorders can also be
connected. MD REC switch allows problem-free recording from any source.
class processor provides unlimited enjoyment of
digital audio at its best.
MMB Type D/A Converter Achieves ZD-Bit Lin-
earity and Super Low Noise
The D/A converter uses the amazing MMB (Multiple
Multi-Bit) principle which delivers topÂ»notch perfor-
mance and sound quality. It consists of six hand-
selected 20Â»bit D/A converters connected in parallel.
This revolutionary approach yields a dramatic
improvement in linearity, THD, dynamic range, and
As can be seen from the illustration, the high-speed
output of an 8-times oversampling digital filter is
connected in parallel to the individual converters.
immediately after D/A conversion, the output of the
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converters is combined while still in high-speed form.
But rather than simply linking the converter elements
in parallel, the MMB circuit drives each converter
separately, so that it can develop its full potential.
Special attention was devoted to phase response at
high frequencies, Parts selection, layout, and wiring
patterns were optimized to achieve perfect phase
matching The end result is performance which sets
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Dc-81 Digital Signal Flow Block Diagram
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THD + noise vs. frequency characteristic
(manner: by varying the number of converters in the tic-01)
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new standards regarding linearity and absence of
distortion and noise.
An important characteristic of the MMB principle is
the fact that it improves performance regardless of
signal level and frequency. The converter therefore
maintains excellent linearity even at extremely low
levels that present insurmountable problems for con-
ventional converter designs. The audible advantages
are immediately apparent as more precise localizaÂ»
tion of sound sources and a heightened sense of
space and ambiance
Ultra Jitter-Free PLL clrcuit
The operation of the D/A converter must be synchro-
nized with the digital audio interface (DAI) signal. For
this purpose. a phase-locked loop (PLL) circuit
generates a master clock which is used as system
reference. If jitter or pulse distortion are present, the
master clock precision will suffer, which has a detri-
lwln alum mowed)
Ultra Jitter-Free PLL Circuit
mental effect on the entire system. The Ultra Jitterv
Free PLL circuit in the DC~61 consists of a preamble
detector and a voltageÂ»controlled oscillator (VCO)
using a quartz crystal element,
Pulse distortion occurs when the signal fluctuates
randomly in the inten/als between "0" and -"1 But
the so-called preamble signal (which indicates the
start of the L and R signals) occurs in regular interÂ»
vals at a constant level, it is not subject to the ef-
fects of pulse distortion. Therefore the DC-61 uses
a detector which extracts the preamble component
from the DAI signal and supplies it to the PLL cir-