SPECTRAL SDR-4000SL Reference CD Processor


The Spectral SDR-4000SL  Used For Sale – We accept Return in 90 Days. Operation has been confirmed, It is in a clean condition with no dirt on the outside. Includes the main unit, power cable, remote control, instruction manual, fuse, hex wrench, and original box.
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The SPECTRAL SDR-4000SL Reference CD Processor is a limited edition reference instrument crafted in the Spectral engineering department and individually programmed and calibrated by its designer Keith Johnson. Relatively unlimited time and resources have been utilized to achieve our ultimate objective: Engineer the most sophisticated and sonically accurate CD player in the audio industry. Those that are familiar with Keith Johnson’s credentials and previous achievements in digital design know this objective is not taken casually or an idle boast.

SPECTRAL SDR-4000SL External dimensions Width 483mm Height 104mm Depth 311mm – Weight 11.8kg.

As with previous editions of our SDR components from the 1980s and 1990s, such as the SDR-1000 and SDR-2000 reference digital components, it takes our engineers multiple design generations to arrive at the final and ultimate model. The SDR-4000SL has been previously produced in two highly regarded versions, the original SDR-4000 and the revised SDR-4000 Pro which incorporates the exclusive HDCD “Long Filter” technology. It has taken Spectral engineers four years more to develop the final and most uncompromising generation, the SDR-4000SL. In the SDR-4000SL, Keith Johnson and the design team address their remaining performance objectives to create the ultimate SDR-4000 and redefine the possibilities of the redbook CD medium in the finest music systems.

The SPECTRAL SDR-4000SL Reference CD Processor is Spectral’s ultimate compact disc player, completing the Spectral Digital Reference system begun with the SDR-2000 Digital Processor. The development program for the SDR components was initiated over 15 years ago with the introduction of the Spectral SDR-1000 Reference Disc System, the industry’s first truly high-end compact disc playback system. The innovative SDR-1000 was years ahead of its time, pioneering fundamental processing breakthroughs such as balanced decoding and conjugate correction filters. More recently, the ambitious SDR-2000 Professional Processor has stunned the audio industry with its technical advances and resolving power. Sharing its uncompromising circuit architecture with the historic HDCD recording system by Pacific Microsonics, the Spectral SDR-2000 is widely considered to be the finest digital processor available as well as the acknowledged reference for High Definition Compatible Digital recordings

The arrival of the SPECTRAL SDR-4000SL Reference CD Processor culminates the SDR program at Spectral and achieves the final integration of our high resolution digital technology. Supporting the challenge are new generation component technologies and state-of-the-art test systems to push forward the envelope of digital audio performance. Like other Spectral SDR components, no detail or expense has been spared in the SPECTRAL SDR-4000SL to achieve the status of a true reference.

Quality In Depth

Engineering refinement in the SPECTRAL SDR-4000SL CD Processor extends to the quality of the user interface as well. The SDR-4000SL front panel is a model of understated elegance and usability, in the Spectral tradition, with a hand polished satin front panel and machined acrylic construction. Large alphanumeric displays monitor the CD drive and playback functions, allowing visual confirmation of remote operations from a distance.

Refinement is also reflected in the convenience and precision of the SPECTRAL SDR-4000SL remote control. The deluxe remote duplicates SPECTRAL SDR-4000SL front panel controls and offers full input keypad and repeat functions. All metal construction of fully machined aluminum alloy components and premium powder coat finishing ensures rugged durability. The instrumentation grade momentary switching used on theSPECTRAL SDR-4000SL front panel is also used on the SPECTRAL SDR-4000SL remote for positive actuation and long operation. Two infrared transmitter diodes maximize signal power for extended operating range.  

A Fundamentally Superior Compact Disc Drive

The Spectral UltraDrive is based on an unusual CD ROM computer drive designed for critical avionics and commercial applications. This high-rel drive stands out from the countless number of drives we evaluated for its superior performance and build quality and is rated at over twice the cycle life of any other premium drive built today. As most remaining optical drives are decontented mass-market models, destined to be phased out in the immediate future, our drive is contracted to be built for avionics and critical military use for many years to come with component parts support extending futher still. In all probability this drive will be one of the few fully drives many years from now. By starting with the most robust and overbuilt CD ROM drive on the market we can assure our customer reliable and extended service life. To minimize the service requirements our drive is a beltless design to eliminate the inevitable need for belt replacement found in most CD drives, including our own earlier SDR components. Our drive also features an extended life laser readhead with full glass optics to furtherreduce service needs. Perhaps the most unusual aspect of the new Spectral UltraDrive is something that it does not have. The UltraDrive has been engineered and tested to be clocked by an external oscillator, it has no clock reference of its own. Spectral engineers then clock directly from the DAC master clock for the highest possible timing accuracy. Slaving the optical drive directly from the DAC clock is acknowledged as the most precise method possible to control data output, but in the real world this ideal approach is never actually implemented in production, the optical drive manufacturers are unwilling to produce drives without clock systems they can test. Spectral UltraDrive is different. We have co-developed the drive electronics to be run exclusively by our own external clock reference. The result is the first optical drive designed and optimized for external clocking.

Modular Approach Addresses Service Concerns

Having built reference CD playback components for over twenty-five years, we are interested in more than high performance alone. In the final edition of the Spectral  SDR-4000SL we wanted to address the challenge of mechanical service on a more fundamental basis. In the past the finest available CD drives have also been the largest and most complex, with elaborate loading, damping and suspension systems. Servicing for the replacement of wear items like laser readheads and drive belts could require extensive disassembly and re-alignment. Our goal in the SDR-4000SL was to eliminate as much of the time and expense as possible. We have designed the UltraDrive as an easily replaceable, self-contained modular system. The UltraDrive is plugged directly into the master clock reference and firmly mounted to a critically damped foundation. The fully modular UltraDrive optical transport makes practical dealer and field-serviceability a reality for our SPECTRAL SDR-4000SL for the first time.

The Spectralock Master Clock Architecture

The pursuit of ever improving clocking accuracy and lower timing error and jitter have been a fundamental priority in every Spectral SDR component since the original. Although generations of high-end audio digital components have previously proclaimed the “banishment” of jitter, careful listening evaluation of even the best of these reveals the clear sonic effects of these insidious distortions. We are under no casual illusion regarding this difficult technical issue: audible consequences of insufficiently precise data timing and noise-induced jitter are still the foremost reason that digital audio fails to deliver on its musical promise. Our new Spectralock Master Clock architecture is Keith Johnson’s most ambitious assult yet on jitter and its sonic consequences. The Spectralock data management system is fully integrated to the UltraDrive optical disc transport. It is completely enclosed and shielded and like other parts of the SPECTRAL SDR-4000SL, its powering floats as if from batteries. Signal transmissions are balanced to self-cancel digital activity and data outputs are slaved from the ultra-precision crystal that direct clocks the conversion to analog signals at the DAC. These design features hide the optical transport and its servo activity to assure always accurate filter processing and prevent any intrusion of the drive to our silent conversion environment. The carefully shielded and interfaced UltraDrive transport contains a fast loading – quick to play data buffer. The Spectralock system grabs the information bursts from the CD and outputs a continuous time invariant stream of data. Twin synchronization loops slave both operations to the DAC master clock so that motors, tracking servos and other activity that would damage timing accuracy are sequestered to create a time stable stealth platform. The Spectralock system is considerably more precise than even the best master clock box systems which have noise induced jitter problems as a result of the long clock cables. Spectral’s fast lock synchronization loops, quick loading buffer and effective isolation strategy all combine to make an ideal platform for pristine timing for processing and conversion. We achieve an industry leading 120 dB signal-to-noise with better than one-part-per-million data accuracy. There is absolutely no presence of any other activities such as ripples, noises, stray fields or any intrusions to the digital waveforms. Our new Spectralock/Ultradrive system produces signals that are an exact replica of those making the recording – nothing added, nothing subtracted or changed.  


The Ultimate Reproduction of Compact Discs 

The SPECTRAL  SDR-4000SL Reference CD Processor is designed to achieve the finest reproduction ever from compact disc recordings. As the prevailing medium of high-fidelity music recordings currently available, state-of-the-art reproduction from compact disc is a Spectral engineering priority. Many performance compromises long indigenous to even the finest digital audio design have been eliminated for the first time. Utilizing a sweeping array of technological advances, the Spectral SDR-4000SL CD Processor extracts new musical coherence and life from fine compact disc recording, proving clear insight into important musical performances of our time.

Is the SPECTRAL SDR-4000SL our last reference CD player? In the Spectral design language, SL models are usually the final versions in an SDR series, and this is the case with the SDR-4000SL. In the here and now, we are confident that there is little possible regardless of cost that could improve the performance of the Spectral SDR-4000SL in any significant way. We believe this is one way to define a true reference instrument. It is also why the SDR-4000SL is worth listening to and owning.

Manufacture Specifications, SPECTRAL SDR-4000SL User Manual Datasheet PDF and Review :



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