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 MMB Digital Processer DC-61


MMB type D/A converter achieves 20-bit linearity and super low noise
Ultra jitter-free PLL circuit
High precision sampling frequency converter
Versatile digital input/output configuration
MD REC switch allows recording from any source
4-pole analog filter with hand-selected components

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.

As we move towards the 2lst century,digital program sources such as CD, MD, DAT and others are occupying Center Stage in the audio arena. hese formats are increasingly found not only in audiophile equipment for home use but also in car stereo systems and portable units as well. The DC-6l is a digital processor designed with this situation in mind. It incorporates Accuphase's extensive know-how in digital 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 principle that guarantees conversion with ultra-high precision. Six hand-selected 20-bit D/A converters are connected in parallel, resulting 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 virtually absent, assuring absolutely faithful conversion of 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 sampling frequency of the input signal to a high-precision 44.l kHz level l 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 electrical Separation, thus preventing sound quality degradation due to high-frequency noise and electrical interference. The analog output circuitry employing 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 DC-6l . This top-class processor provides unlimited enjoyment of digital audio at its best.

MMB Type D/A Converter Achieves 20-Bit Linearity and Super Low Noise

The D/A converter uses the amazing MMB (Multiple Multi-Bit) principle which delivers top-notch performance and sound quality. lt consists of six hand-selected 20-bit D/A converters connected in para11el. This revolutionary approach yields a dramatic improvement in linearity, THD, dynamic range, and S/N ratio.

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 converters is combined white 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 Ml 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 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 revel and frequency. The converter therefore maintains excellent linearity even at extremely low levels that present insurmountable problems for conventional converter designs. The audible advantages are immediately apparent as more precise localization of sound sources and a heightened sense of space and ambiance.

Ultra Jitter-Free PLL Circuit
The operation of the D/A converter must be Synchronized 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. It jitter or pulse distortion are present, the master clock precision will suffer, which has a detrimental effect on the entire system. The Ultra Jitter-Free PLL circuit in the DC-6l consists of a preamble detector and a voltage-controlled oscillator (VCO) using a quartz crystal element.

Pulse distortion occurs when the signal fluctuates randomly in the intervals between "0" and "1". But the so-called preamble signal (which indicates the start of the L and R signals) occurs in regular intervals at a constant level. It is not subject to the effects of pulse distortion. Therefore the DC-6l uses a detector which extracts the preamble component from the DAI signal and supplies it to the PLL circuit, for elimination of pulse distortion. The VCO uses a quartz crystal oscillator element with a very narrow locking range and optimized loop filter constant, to remove any jitter components from the preamble signal.

* Guaranteed specifications are measured according to EIA standard RS-490.

* Specifications and design subject to change without notice for improvements.

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