The SDR-4000SV 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. 
 
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-4000SV 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-4000SV.  In the SDR-4000SV, 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 SDR-4000SV 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 SDR-4000SV 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 SDR-4000SV to achieve the status of a true reference. 
 
Why A Reference CD Player Is Still Necessary
With the recent introduction of digital playback formats for consumers such as DVD-A and SACD,  it would seem only logical that new digital audio playback components should support these new recordings as well as the established compact disc format. In truth, for general applications, affordable universal disc players may well become the accepted norm for playback of digital audio recordings. In-depth examination of these new high-bit technologies, however, reveals stunning performance limitations when considered for applications of the highest quality. The mass-market origin of the new high-bit digital audio technologies precludes their inclusion in the finest 16 bit CD playback applications due to an array of engineering limitations and performance compromises. Simply put, 24/96 digital audio technology reproduces conventional 16 bit compact disc recordings poorly. In point of fact, reproduction of CD recordings in today’s DVD-A and SACD players is arguably a step backwards, with poorer sonics than previously achieved in CD only players and processors.
 
We find the technical compromises of the high-bit systems far too serious to ignore when reproducing compact disc recordings. An important musical heritage has been captured in the thirty-two years since the introduction of the compact disc digital format, containing some of the finest musical performances of the twentieth century. It is technically clear that the best reproduction of these compact disc recordings will only be accomplished with dedicated CD playback components. Developing a dedicated CD playback system capable of achieving ultimate possible reproduction from compact disc recordings is the goal of the Spectral SDR-4000SV Reference CD Processor. Ultimate reproduction from compact disc recordings is assured by the SDR-4000SV Reference CD Processor. 
 
Unmatched Conversion Accuracy
Spectral's two decades of state-of-the-art digital audio design experience are essential when it comes to extracting maximum performance in the critical DAC stage. Digital to analog conversion within SDR-4000SV is performed at an extraordinarily high level of accuracy and features a Spectral-developed, double balanced implementation of the Analog Devices AD1853 multi-bit Sigma/Delta DAC. This unusual multi-bit double push-pull architecture is a proprietary Spectral innovation achieving DAC resolution and accuracy unrivaled by any other system. Directly inspired by the uncompromising discrete DAC topology of the Spectral SDR-2000 Professional Processor, the SDR-4000SV DAC utilizes a differential current (I/V) conversion stage with Spectral’s own dedicated DAC amplifiers.

Spectral SDR-4000SV is the Industry's Finest CD Playback System
The industry leading performance achieved by the first SDR-4000 twelve years ago continues with the advancements of the SDR-4000SV today. No other digital component for CD playback approaches the challenges of 44.1 digital with the technical and design superiority realized in the SDR-4000SV. This superiority starts with a fundamental architecture dividing 4000 structure into eight fully independent and powered digital and analog sub-systems. Each sub-system has been realized with breakthrough technology and componentry using "best practices" employed in SOTA high-technology instrumentation. With zero cost-cutting and the finest components in existence, benchmark performance in 44.1 reproduction has been achieved. The addition of the new SV technology to the SDR-4000 results in the finest performing CD playback system in the industry, delivering unrivaled performance and the ultimate reproduction of music recorded on compact disc.