Spectral Unveils the SDR-4000SL Master CD Processor
Spectral Audio , the northern California company whose director of engineering is Prof. Keith O. Johnson, gave the first public preview of its SDR-4000SL Master CD Processor on September 24, at Music Lovers Audio, in Berkeley. Introduced by Johnson and Spectral founder Richard (Rick) Fryer, the $19,000 Spectral Digital Resolution (SDR) model sounded sensational playing 16-bit/44.1kHz, HDCD-encoded files Johnson had made for Reference Recordings, through a system that included Spectral's DMC-30SS preamplifier and monoblock amplifiers, Wilson Audio MAXX 3 speakers, Spectral Ultralink II speaker cables, the MIT Z Duplex conditioner, Synergistic Research's controversial ART system, and other room treatments.
Fryer, who cut short his graduate studies in psychology to found Spectral Audio in 1977, when he was 23, noted that his company's marketing style is decidedly low-key. No wonder: demand for Spectral products is so high, and production so limited, that only 900 units of the SDR-4000SL's predecessor, were manufactured between 2003 and 2011. Samples of the SDR-4000SL have yet to reach most of the company's dealers in the US and abroad, but I was told that already the waiting list for it exceeds the initial production run.
"Don't count 44.1kHz and CDs out," Fryer proclaimed at the start of a lengthy, technically complex introduction that he delivered without a single hesitation. "If 44.1 is implemented well, it is high-resolution. The problem is, there is little in the high-end digital arena that really is very good. CDs have an inherent nature all their own that needs to be supported by the finest technology they were designed for. If you want to hear the best that 16/44.1 can deliver, you have to revisit the technology, as we have, and develop a one-piece, single-box solution dedicated solely to the CD."
Fryer and Johnson set about to merge their finest transport and playback technologies into a single, "price has never been an obstacle" box. Separating CD-player technology into its six or seven subsystems, Fryer said, they "turned over every stone" to build, from the ground up, a one-piece component that would deliver sound similar to that of the legendary Pacific Microsonics Model 2 processor.
Among the weaknesses of traditional CD players that they addressed were clock-induced jitter and the limitations of op-amps and integrated circuits. Favoring discrete circuits that foster "continuity and brilliance," Johnson spent years designing a complex DAC interface-actually, an aggregate of eight separate amplifiers. This architecture is designed to present the DAC with an unmatched conversion environment, and to provide exact waveforms that are then processed by passive analog filters. Johnson stated that, unlike integrated circuits, his discrete circuit's internal state never changes-a feature that, Fryer claims, sounds like analog. Other dedicated discrete circuits are applied to Spectral's reference DMC-30SS preamplifier and the SDR-4000SL's line section.
The Spectral team then evaluated dozens of transports, before partnering with an Asian company to modify one of their models. The result is what Spectral claims is an "exceptionally silent" or stealth transport that is slaved directly from the DAC. Signal paths are fully balanced and isolated, resulting in clock-derived buffered signals with apparently no trace of rotation, vibration, servo, or other mechanically or electrically sourced artifacts that can cause jitter and thus degrade signal conversion. Gone are belts, isolators, or rubber parts, which degrade over time.
"Our machine reproduces many traditional test signals more accurately than commercial test equipment," Johnson claimed. "Because the smallest amount of noise will mess things up, we minimize accessories, and slave everything in the DAC to a dedicated fixed-frequency crystal. We also use floating, battery-like power to isolate most parts of the machine from one another. Given this silent conversion environment, where everything functions in analog class-A, we end up making manufacturers' parts work and sound better than they ever imagined possible."
Johnson and Fryer say that Spectral will "someday" develop a high-resolution file player. Meanwhile, they're convinced that the SDR-4000SL Master CD Processor functions at such a high level that there is little difference between the sound of well-recorded CDs through their player and the best current playback devices for higher-resolution files.
After almost an hour of explication, Johnson played excerpts from a few 16/44.1, HDCD-encoded tracks from the Reference Recordings catalog. I was so blown away by the extremely long decay time of the triangle in Benjamin Britten's Young Person's Guide to the Orchestra (Michael Stern, Kansas City Symphony, RR-120 CD) that I asked Johnson for an explanation. He replied that while "Red Book" CDs lack enough bits to reproduce such die-offs in their entireties, HDCD's code adds a bit or two that sustains them to their natural ends.
If the triangle pricked up my ears, the unexpectedly huge drum thwacks in an excerpt from Britten's Sinfonia de Requiem, from the same disc, were so startling that I literally jumped a bit in my seat. (I was seated in the first row, somewhat in line with the left-channel Wilson MAXX 3.) As Johnson played a few more examples, it was easy to hear the difference between the drier sound of miking in a large arena with virtually no early reflections, and the wetter sound of swing music captured in a small hall. By the end of the Reference Recordings portion of the demo, I was certain that, in terms of dynamic range, dynamics, smoothness, and control from top to bottom, Johnson, Fryer, and the folks at Spectral and Music Lovers Audio had treated us to the most sensational demo I'd ever heard. After the Spectral men had left the demo room to schmooze elsewhere, Music Lovers' Hugh Fountain played some more selections. Burns of older CD tracks to CD-Rs, as well as a superior remastering of a classic Santana album, further confirmed that the Spectral SDR-4000SL Master CD Processor was taking no prisoners and telling no lies. If the CD it played had problems, we heard them. But when the recording and pressing were superb, we were rewarded with far more of their musical bounty than is the norm.