PS Audio UltraLink D/A processor Corey Greenberg, January 1993

Corey Greenberg, January 1993 (Vol.16 No.1)

The new Theta DSPro Basic kills the old in every possible dimension. But how does it compare to its similarly priced competition? As Digital Lad tagged PS Audio's $2000 UltraLink as his first choice in a digital processor under 2k, I asked PS Audio to lend me an UltraLink so I could compare the two overachievers.

I should note that while the UltraLink comes with balanced outputs as standard equipment and the Theta's balanced outputs add $400 to its price, the method in which each processor derives its balanced outputs is significantly different. The UltraLink employs a single stereo 20-bit UltraAnalog DAC for both channels, and splits the DAC's analog outputs into + and – signals after the DAC converts the digital signal into analog.

As I described earlier, the Theta splits its digital stream before the DAC, with each PCM-67 DAC decoding the + and – halves of the balanced digital signal. Theoretically, this results in cancellation of both clock-signal artifacts riding on the output signal and other distortions inherent in the DACs themselves. Throughout these comparisons, both the Theta Basic II and the PS Audio UltraLink were driven by the Theta Data II's AT&T optical output.

Taken from their unbalanced outputs into either the Melos SHA-1 or Classé 5 preamp, the two processors' distinctly different characters were obvious and striking. The UltraLink excelled in the areas of HF smoothness and clarity, while the Theta was much more dynamic, as well as far more rock-solid in the low end. The UltraLink was the picture of politeness, while the Theta rocked the house. If the two processors were pianists, they'd be Bill Evans and Little Richard; even though I dig the Quintessence record Robert Harley bought me last time we hung in Austin, I never saw Bill Evans play the piano by leaping into the air with a whoop and crashing down on the keys with his butt, and in my book, playing the piano with your butt trumps introspective chord clusters hands down!

Unlike RH, I didn't hear any of the excessive midrange forwardness he reported, but then it's also possible that the Theta, my only point of reference to the UltraLink at the time, has a similar forwardness. Even so, with any combination of the gear I listed earlier, I never felt that either processor's midrange was too prominent or pushed forward; comparing well-transferred CDs like the MFSL gold Slowhand and AudioQuest's Luke and the Locomotives to their vinyl counterparts, both processors did an excellent job of preserving the spectral balance of the original recordings. While it's entirely possible that component interactions could have accounted for the UltraLink's midrange forwardness noted in Bob's review, I didn't hear it. On my own "Eden" recording, the guitars had the correct midrange timbres with either the PS Audio or Theta processor.

But while the UltraLink struck me with its utter cleanliness and smoothness through the midrange and high end, extended comparison with the Theta showed it to be a little too smooth. This is a characteristic I've heard from UltraAnalog-based processors in general, like the Levinson No.30, Audio Research DAC1-20, and VTL Reference; while these processors are arrestingly smooth and clear at first listen, I find them to subtly "clean up" every CD they're fed, even if the CD isn't that clean to begin with.

Unless you're intimately familiar with the sound of a recording before its conversion to digital, though, it's impossible to say whether the UltraAnalog-based processors are actually more accurate than others or, in fact, impose their own sonic signature on the music. Turning again to my "Eden" recording, I have to say that the sound of this track with the Basic II in the chain was much closer to the sound of the original analog two-track master than the UltraLink, which rendered the purposefully distorted Stratocasters as much less hot and aggressive than the original master. Interestingly, Bob Deutsch also noted this "cleaning-up" of "Eden" in his "Follow-Up" of the UltraLink in Vol.15 No.9, but as he hadn't heard the original master tape, RD understandably assumed that the UltraLink was "stripping away" distortion to get to the real sound of the track. As it turns out, the UltraLink did make "Eden" sound cleaner than the Theta, but it was the Theta which came closer to re-creating the original sound of the track, not the UltraLink.

Still, the Theta wasn't perfectly neutral either. With both processors taken from their unbalanced outputs, I felt the Theta's highs to be slightly harder and less open than the UltraLink's. Even though its performance in this area was leagues ahead of the original Basic, the new Theta still retained a bit of bite in the upper midrange and high end that showed up most dramatically in head2head comparisons with the Linn and Well-Tempered analog rigs. If all you're used to is the sound of more run o'the mill digital playback like the Rotel and Adcom players and you get a chance to hear the Basic II, you'll think I'm insane. But compared to both the sound of the UltraLink and good analog, the Theta did have a very slight but noticeable hardness in the upper mids and highs.

While already wide and well-defined, the Basic II's soundstaging capabilities swelled to the bursting point when I switched over to balanced hookup. On the "Angels With Dirty Faces" track off Kiko, there are handclaps and shaker sounds that appear beyond the right and left speaker positions, respectively; the handclaps, in particular, are pretty far outside the right speaker if your system can "do" this kind of thing. Over the UltraLink, the soundstage was extremely well-defined, but the handclaps and percussion were only slightly to the outsides of the speakers. With the Theta, on the other hand, these sounds moved several feet beyond where the UltraLink had placed them, giving the whole presentation a much larger, more dramatic perspective. Other "outside" images that were consistently farther outside the speaker positions with the Basic II were the solo vocalist on JA's Elgar recording on Stereophile's Test CD 2, and especially the "Well done!" at the very end of JA's Chopin recording on Test CD 1; I have never heard this voice sound as far beyond the left speaker as with the Basic II in the chain.

Depth, too, was an area where I felt the Theta edged the UltraLink. As strong as the PS Audio processor is at fleshing out the sound of well-recorded CDs from front to way, way back, the Theta consistently outdistanced its rival. Track 2 on Kiko, "Wake Up Delores," features the rhythm guitars of David Hidalgo and Cesar Rosas right up front and panned hard left and right, with Louie Perez's drum kit set farther back in the mix in the center of the soundstage. Whereas the UltraLink portrayed these disparate instruments as clearly defined in space from the rear of the soundstage to the front, the Basic II gave much more of a sense of real musicians in a real space; the triangle of air between the two guitars and the drum kit was much larger and more believable than with the UltraLink. The Theta's ability to re-create a vast and vividly defined soundscape with the appropriate recordings is unbelievable, in my experience equaled or exceeded only by two processors: Theta's $5400 Generation III and the Levinson No.30.

In overall ease, the balanced Basic II was, again, superior to the UltraLink. While the two processors are very competitive when run single-ended, the margin becomes much wider when they're run balanced; the UltraLink's sound doesn't really change when you go to balanced operation, while the Theta becomes vastly better from A to Z. Either one of these two units is in the top five best digital processors at any price, but the balanced Theta was clearly a cut above the UltraLink.

I think the most telling account of any audio component is the type of music you tend to subconsciously "match" it with to show off its best attributes. When I've got a piece of gear here for review, I naturally gravitate toward the recordings in my collection that will demonstrate what it can and can't do; the intrinsic character of the gear under review always seems to "call out" for certain kinds of music after I live with it for awhile.

With the UltraLink in the chain, I found myself listening to more sedate, audiophilesque recordings like Clapton's Unplugged and the Cowboy Junkies' The Trinity Session, digging the crystalline clarity and soothing relief from digititis that are the UltraLink's strong points.

With the Theta, though, I cranked up the Zeppelin, Dan Baird's hot new Love Songs for the Hearing Impaired, and the Red Devils' almighty King King, as well as the rhythmically intense Kiko. The Basic II just has so much more pace, slam, timing, whatever British appellation you want to tag it with; the Theta's got rhythm like no other digital processor I've heard except the Gen.III. And as my listening diet consists of mostly groove-heavy music, I was never really happy with the sound unless I had the Theta hooked up.

Switching to the terrific-sounding UltraLink was never disappointing, but the whole "feel" of the system changed dramatically, and music that depended on a strong sense of rhythm just didn't come across as viscerally as with the Theta. If my tastes ran more toward softer, gentler types of music, I'd probably prefer the PS Audio processor.—Corey Greenberg

Pothes's picture

Would you recommend this dac over msb analog and Hugo TT or it is old to to step up and take over these two ?

Will you review mola mola dac

Thanks Robert .

John Atkinson's picture
Pothes wrote:
Would you recommend this dac over msb analog and Hugo TT or it is old to to step up and take over these two?

The PS Audio truncates data with bit depths greater than 16 so is not competitive with modern DACs.

Pothes wrote:
Will you review mola mola dac?

No plans to do so at present.

John Atkinson
Editor, Stereophile