Digital Processor Reviews

Imagine an electronic magic wand you could wave at your listening room's acoustical problems to make them disappear. The Cambridge Signal Technologies SigTech TF 1120 may be just such an alchemical device. Its efficacy depends on the nature of the acoustical warts in your listening environment. Operating solely within the digital domain, the SigTech device can perform both drastic and subtle frequency-response and time-domain corrections that are beyond the scope of analog-based units. While the TF 1120 is expensive, in some situations it may still be the most cost-effective way of coping with acoustical gremlins. Is it the solution to your problems? Perhaps.

Let's say you play a CD on a poor-quality CD transport and store the digital audio data in a massive computer memory. You then repeat the process, but this time play the CD into the memory from the finest CD transport extant (say, the Mark Levinson No.31). A week later you feed the two sets of data from the massive memory into a digital processor and listen to the music. Would the CD transports' sonic signatures be removed from the signal? Could you hear a difference between the transports a week later?

With the introduction of Audio Alchemy's Digital Transmission Interface (DTI) more than three years ago, the company created an entirely new category of hi-fi product: the jitter filter. The original DTI was a good start, but didn't always improve the sound of the better-quality digital front-ends.

The availability of the Pacific Microsonics High Definition Compatible Digital (HDCD®) PMD100 decoder chip, manufactured by San Jose's VLSI Technology, has brought about a minor revolution in Compact Disc playback. It brings sonic improvements in imaging, soundstaging, and resolution of detail. In the past six months, Stereophile has published a number of reports on the HDCD decoder's operation, what HDCD recordings are available, and the improvements brought by the HDCD chip to specific digital audio processors (footnote 1). High-end manufacturers are incorporating the $40 HDCD chip in their newest decoders, including the $4695 Sonic Frontiers SFD-2 Mk.II D/A processor, the $15,950 Mark Levinson No.30.5, and the $8195 Spectral SDR-2000 Professional HDCD D/A Processor (reviewed in Vol.18 No.5).

The EAD DSP-1000 III is housed in a 2.5" high, U-shaped chassis with a brushed-aluminum front panel. The cover is made of solid, 1/10"-thick steel with a nice "powder" finish, giving the unit an expensive feel. A pushbutton standby switch sitting below a green LED indicator sits at the panel's left. Even when set to Off, power is maintained for the decoder's circuits, but the digital inputs and analog outputs are muted. To the right, three pushbuttons allow selection of one of the three digital input sources (TosLink, 750 ohm coaxial, or glass optical interface). Like the EAD DSP-7000 unit reviewed by J. Gordon Holt and Steven Stone (Vol.18 Nos.1 & 5), the DSP-1000 accepts any of the three sampling rates: 32kHz, 44.1kHz, or 48kHz. Toward panel center is a lock light that illuminates when a digital data link is established. HDCD decoding occurs automatically whenever an HDCD disc is played, causing the front-panel HDCD indicator to light. No remote is available for this decoder.

To echo Audio Cheapskate Sam Tellig, who was in turn paraphrasing Thomas R. Marshall, what the world needs is a great $299 CD player. Certainly there's no shortage of expensive units vying for your attention—most of them consisting of separate transports and D/A converters.

Spectral is a bit of an enigma in the high-end audio world. Although nearly 20 years old and one of the founders of the American high-end audio industry, Spectral isn't a name that comes quickly to mind when considering the best of the best in high-end.

Spectral's low profile is of their own choosing. They advertise very little, their products are demonstrated in a small number of stores, they almost never send products to magazines for review, and they are very quiet about their accomplishments.