Digital Processor Reviews

The DSPro Basic's soundstage depth seemed to combine synergistically with its remarkable transparency. There was no sense of veiling, congestion, or fog. Instead, the Basic provided a transparent window on the music that was luscious and inviting. Music had an openness and clarity seldom heard from digital playback at any price. This transparency, coupled with the ability to reveal spatial nuance, allowed me to see into the music as though it were clear crystal. Instrumental outlines were resolved in three dimensions, with air and space around them. Images floated between, above, and behind the loudspeakers. Female vocal (Diane Reeves on David Benoit's This Side Up, En Pointe ENP 0001) was pure, clear, and seemed to exist in my listening room. In addition, the DSPro Basic had the ability to convey instruments' individualities during complex passages without homogenizing their sounds. The only other processor I've heard that surpassed the DSPro Basic in this regard was the $12,000 Stax DAC-X1t.

Equally impressive was the DSPro Basic's ability to reveal musical detail. Percussion instruments had sharp, clean, transient attacks without being up-front or aggressive. Instead, they had that quick leading edge, but in their correct spatial locations behind the musicians. Detail tended to be immediate rather than laid-back. The word "vivid" is an appropriate description of the DSPro Basic's presentation. The acoustic guitar on my duet recording (track 12 of the Stereophile Test CD) had a clean, sharp attack, at the same time surrounded by a dynamic bloom. Playing back the CD Dick Hyman Plays Fats Waller (Reference Recordings RR33CD) confirmed this impression of the DSPro Basic's quick transient ability. The sound of the hammers hitting the strings was apparent, but not overly so. It was very similar to the actual live sound of the Böosendorfer I heard during the recording session.

The tonal balance was smooth, with a surprisingly clean treble. No trace of digititis here. The upper octaves were devoid of the hash and grundge that so often mars CD playback. Although I would not characterize the HF presentation as sweet and silky in absolute terms like the Stax X1t, it was nevertheless relatively free from fatiguing grain and harshness.

Dynamic impact and ability to reveal subtle dynamic contrast were superb. The DSPro Basic's ability to deliver punch and visceral impact added a rhythmic urgency to music. Low frequencies were round and liquid, yet detailed. The string attack of acoustic bass was readily audible (Eddie Gomez on the first Steps Ahead album, Elektra/Musician 9 60168-2), its pitch and body intact. Bass drum was clean and taut, without tubbiness or bloat. This added a rhythmic intensity to music that involved the listener in the performance. Overall, the DSPro Basic provided a thoroughly involving and inviting musical experience.

To find fault with the DSPro Basic, I must turn to the extraordinary Stax DAC-X1t. The Basic is that good. The DSPro Basic lacked the analog-like sense of ease that made the X1t so pleasurable. In addition, the treble presentation from the tubed X1t was smoother and warmer. During the auditioning, I thought that the DSPro Basic's rendering might be detailed to the point of being overly analytical. Whether this is an artifact of the processor or a revelation of what is actually on the disc, I don't know. This has been a source of recent debate. It has been argued that some of the good-sounding processors tamper with the presentation to make it more "musical" at the expense of fidelity to the source. This is a difficult but vitally important question to resolve.

There is a way, however, to know exactly what a digital processor is doing to the sound, though I was unable to implement it in time for this review. As soon as I've finished this review, I'm meeting Bob Katz in California, bringing with me the original ½" analog master tapes of Stereophile's Poem LP for conversion to digital. The tapes will be played back on Kavi Alexander's machine, on which they were recorded, and converted to digital with several leading-edge A/D converters. After editing (assembling the tracks in the correct order with the appropriate amount of space between them), CDs will be manufactured from the edited digital master.

Concurrently, Stereophile has purchased an Ampex ATR-100, a full-on professional analog tape machine for playing back our &#189" original master tapes. We will thus have the uncorrupted and ultimate reference (the analog master tape) and a CD made from that tape, decoded by the processor under scrutiny (footnote 3). This is by far the most revealing test of a digital processor's editorial influence on the sound: it will stand naked with its flaws and euphonic colorations exposed.

Conclusion
To say I liked the Theta DSPro Basic is an understatement. It provided a level of musicality I would never have expected at this price. In fact, the DSPro Basic is the best digital processor I've heard at any price, except for the $12,000 tubed Stax DAC-X1t. It had all the attributes of the best digital playback: a deep and transparent soundstage, smooth tonal balance, spatial detail galore, and textural liquidity. It was the antithesis of the flat, harsh, sterile sound that characterizes many digital processors, especially the budget models. I can't wait to hear Theta's DSPro Generation II, their top model.

It's significant that I'm forced to compare the DSPro Basic to the Stax DAC-X1t to reveal the former's shortcomings. No, the Basic didn't have the Stax's sense of ease, smoothness, freedom from fatigue, and ability to resolve finely woven detail. But for $2000, it came far closer than one might imagine. My only criticism is that the DSPro Basic's presentation tended toward the overly detailed and analytical, which did create fatigue after extended listening sessions. Whether this is an accurate portrayal of what's on the disc or an artifact of the processor is an open question.

I'm concerned, however, about what appears to be the DSPro Basic's fundamental inability to decode a 48kHz signal from a DAT machine. This may become a significant issue as DAT machines hit the stores soon. (See my CES report next month.) I confirmed, however, that the problem can be corrected in software with new ROM chips: Theta has a good track record of updating customers' units.

The DSPro Basic clearly breaks new ground in affordable digital playback. It represents a quantum leap in what we can expect from a $2000 processor. All contenders for the title of best reasonably-priced converter must regard the Theta DSPro Basic as the benchmark against which all others are judged.

Get out your checkbook, Michael. The Theta DSPro Basic is exactly what you've been waiting for.

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Footnote 3: This is not quite true. The ultimate reference for this recording is the real musical performance, which only Larry Archibald, John Atkinson, Richard Lehnert, and Kavi Alexander were fortunate to have experienced.