Digital Processor Reviews

Art Dudley wrote about the HoloAudio Spring DAC in July 2018 (Vol.41 No.7):

Praise it all you want, but digital audio is still my second choice: In a life in which the enjoyment of art is infinite but the hours in which to do so are limited, and given the choice between listening to LPs and 78s on the one hand or files and CDs on the other, digital is a waste of my time: It doesn't connect me with the music as well as analog does, period. In my experience, digital audio isn't evil, merely banal.

But digital is getting better all the time, and part of my job description is to endure in meeting digital halfway, to give it a fresh chance every time out. But first I have to catalog and discard all of the defense mechanisms I've adopted without thinking—the wince before the blow, if you will—to make digital more palatable. In particular, because early digital sound was so damned bright, even when the glare isn't there, my ears still squint.

So it was that, during my first hour with the HoloAudio Spring "Kitsune Tuned Edition" Level 3 DAC,6 I thought: Is it my imagination, or is this thing a little . . . dark?

It turned out to be the former. The darkness was all in my head, a semisubconscious product of my expectations. I remember using my Sony SCD-777 SACD/CD player to listen to "Two Turns Home," from guitarist David Grier's Evocative (CD, Dreadnought 0901), then to an AIFF file made from that same disc, played through the HoloAudio DAC—and the latter sounded, undeniably, a lot richer. The electric bass was more rounded, the fiddle more substantive, the guitar more burnished in tone, and the recording as a whole was more listenable. I made a conscious effort to let down my guard, and found that nothing—and I mean nothing—in the music was hidden from me. The notes were no less apparent, the pitches no less distinct, the ensemble playing no less rhythmically accomplished than when listening to the CD. Subtleties of bassist Victor Wooten's technique and details of his fretless instrument's sound were front and center, and Grier's melodic variations rolled, colorfully and altogether beautifully, into aural view, one after the other. I was more than enchanted—I was involved.

I couldn't help but wonder: Was this uncommon musicality a consequence of HoloAudio's similarly uncommon approach to digital processing? As Herb Reichert noted in his review of it in the May 2018 Stereophile, the Spring DAC Kitsune Tuned Edition" Level 3 is unusual, though not entirely unique, in using a resistive ladder to passively convert the incoming bitstream to AC voltage. Allied with this is a second and arguably equally crucial distinction: Although the user can apply to the incoming signal one of three different switch-selectable oversampling filters, in its default mode, the HoloAudio Spring plays music with no oversampling.

Again, I wondered: Is it a coincidence that one or both of those distinctions have been found in some of my all-time-favorite digital source components, including D/A converters from Audio Note, 47 Laboratory, and Wavelength . . . ?

As Herb also pointed out, conversion via a resistive ladder can be accomplished by means of an integrated circuit—the Philips TDA-1540 family of chips, which flourished in the 1990s, being a prime example—or by discrete resistors. The latter route is extremely labor-intensive, requiring the tedious measuring and hand-selecting of every resistor used. Building a discrete-resistor ladder DAC is expensive for that reason, and because hand selection usually means discarding a certain number of out-of-spec parts. And if the builder wants to use boutique resistors . . . well, as the monkey said as he peed into the till, That's running into money.

I've had the pleasure of listening to a Stereophile-recommended, Class A+ discrete-resistor ladder DAC: the TotalDAC d1-tube-mk2, which I heard at Michael Lavorgna's music barn in the forests of New Jersey. It was sublime. It also cost €9100—in dollars, a five-figure price tag. So when Herb told us that HoloAudio's discrete-resistor ladder DACs sell for as little as $1499, and that the subject of his review—the company's all-out, silver-wired, Mundorf-capped "Kitsune Tuned Edition" Level 3—costs only $2499, the Holo became the rare digital source that I begged to hear.

* * *

So here I was, doing just that, feeding the Spring DAC with files from my Roon-equipped MacBook Air computer, connected via USB—in which case the Spring can handle PCM up to 32-bit/384kHz and DSD up to DSD512. I moved from acoustic guitar at 16/44.1 to solo piano at 24/96: Chopin's Ballade in g, from Daniel Barenboim's On My New Piano (AIFF file, Deutsche Grammophon 289 479 6724). And here I could point to how the Holo put across the considerable size of Barenboim's unique, straight-strung instrument, conceived by him and built by Chris Maene, in particular the texture and purr of its lowest strings, and how the sound of the recording space was realistically and, I dare say, naturally intertwined with the sound of the instrument, as opposed to sounding like tacked-on generic reverb. But the two things that most impressed me were the fact that the Spring DAC communicated how much Barenboim was enjoying playing the piece—you can just tell!—and how, at about 7:17 in, when he goes up an octave for a high B-flat, that note just hung in the air, as solid and as meaty as I'd expect a good LP to let it sound. I remember how Naim Audio's founder, the late Julian Vereker, used to say that if a CD player could make just one disc sound good, then there was hope for digital. I'd settle for one note—and there it was.

All right, make it three things that most impressed me: What is that scary sound at 5:30 in the Chopin, and again at 5:33? Is Barenboim slamming his left foot down on the stage as he plays those chords, or is it a structural sound resulting from his having struck the keys so hard? I have no idea, but it was cool, and I'd certainly never before heard it from this file.

It was time to throw at the Spring a few bad, or at least so-so, recordings. It sailed through them all, not only by making the best of badly recorded sound without throwing a blanket over it, but by playing the music so well and so convincingly that I was too charmed and entertained and delighted to devote my attention to audiophile froufrou. "Long Ago and Far Away," from the dB's' Falling Off the Sky (AIFF from CD, Bar/None BRN-CD-202102), elements of which are recorded so close-up that it's a little too in-my-face and borderline edgy through most DACs, was unbelievably good: sonically sparkly but not at all wince-inducing. And, for gosh sakes, Will Rigby's drumsticks on his cymbals, recessed in the mix, sounded just like drumsticks on cymbals: You can't teach a DAC that's merely rolled-off on top to do that.

The listening described above was done without oversampling. For this Follow-Up I also relied on PCM rather than native DSD; the latter, according to distributor KitsuneHiFi, is heard at its best via the Spring's I²S input, which would require a digital-to-digital USB-to-I2S converter (Kitsune sells such things, starting at $399) and an I²S-over-HDMI cable. My primary goal was to hear what a modern, zero-oversampling DAC sounds like, and in that context I was not only impressed, I was overcome with the sort of unexpected delight that discourages further acts of daring. (I'm one of those people who, on trying a new restaurant and finding a dish I like, never orders anything else.) But access to the Spring's oversampling filters can be had with the press of a button, so I tried them, too.

Relative to the believable color and life of the Spring's music-making, all three of its oversampling filters added different amounts and flavors of death and dullness, blunting the sense of human force behind note attacks, sanding off all the randomness, and replacing the charged air around notes with something that sounded like it was molded from plastic. One example of the above came while listening to Tony Rice Plays and Sings Bluegrass (AIFF from CD, Rounder Select ROUCD 253). Near the end of "I've Waited as Long as I Can," Rice begins his solo with a D produced by bending his guitar's B-string to that pitch before his pick attack: in non-oversampling mode, the tension involved in doing so was apparent; with each of the oversampling filters—especially the third, which oversamples all incoming digital signals, regardless of provenance, to DSD—the tension was nowhere to be heard.

The above points to the only complaint I have about the HoloAudio DAC, though it's less a complaint than a suggestion: Why not make a version of the Spring that dispenses altogether with the oversampling chip, and with the controls required to activate those filters? Maybe such a thing could sell for even less than $2499.

Never mind that. I'm just happy that so relatively affordable a product has proven me wrong in the most agreeable way: The HoloAudio Spring "Kitsune Tuned Edition" Level 3 DAC is a revelation in every sense. As Herb said: Highly recommended.— Art Dudley