Glass ceilings & flies.
My wife and I do a 1-hour morning meditation called Nadabrahma which Osho synthesized from a Tibetan technique. The first thirty minutes are accompanied by a Deuter soundtrack of assorted singing bowls, bells and sundry struck metallic objects. Saying that I know this well isn't exaggeration. In my review of Wyred4Sound's Stage II upgrade to their STP-SE preamp, I'd talked of how, over the standard, it had virtually upgraded our tweeters. That's because on this simple yet telling track, fine decays lasted longer, harmonically loaded transients rose steeper. Now the Adagio upped the same game once more. Sounds so faint and silvery that I can only describe them as "glass flies rubbing their legs together" flared behind far louder bells that I'd not heard before; or in far reduced shorter versions. Also, the overtone content of each strike, of each faraway triangle tickled rapidly inside one of its elbows, was more loaded and far more precisely fixed in space. It gave the entirety of this track a finer more light-filled and filigreed quality plus superior location specificity. This reminded me of Stereophile's walk down the CES 2017 aisles with ukulele master Jake Shimabukuro. Comparing himself live versus on-the-spot recorded playback via various statement systems, a constant observation of his was that playback's treble energy was lower. I believe here the commentators failed to account for the fact that nobody hears an instrument like the one who plays it. Certain upper-harmonic content—the fizz around an overtone halo's edge if you will—is so faint that it doesn't carry across hardly any distance at all. The player himself hears it because he's that close. Nobody else does. What the Adagio did now seemed to pursue this belief. Without any reshuffling of soundstage distances, it captured... well, the treble equivalent of pixy dust. To hear it at this degree of reveal did, admittedly, necessitate an upgrade from the nCore 500 monos to the class A Pass Labs XA-30.8. Class D's treble wasn't astute enough. Here I would certainly hope that a quad stack of dCS or a priceless MSB reference achieves this or more but in the <€10'000 realm where I play, I'd never before heard this level of microscopic recovery. Achieving it with such non-lossy volume to transmit at low SPL which set the minuscule stuff at the very edge of my hearing... that broke through a personal glass ceiling.

Before you shrug it all off as irrelevant like the rustle of a turned score three rows deep into the second violins... it's simply one example of a track I know intimately. Here it happened to be the most spiderwebby of harmonic glitter, swirls and barely singed metal. On a standard music track, it becomes the clacking of a woodwind's keys plus more complete timbre. While we can agree that mechanical fingering noises are musically irrelevant, they do heighten the illusion of a player's presence and activity. Meanwhile a harmonically more complete tone signature of a given instrument is most certainly musically and not just technically meaningful. It unpeels finer tone modulations which lead to more timbre diversity like expanded dynamic range. That's how microscopic stuff translates. It's a higher degree of virtual reality. Whilst it can mean more hidden notes as in background stuff you didn't make out before, it's primarily micro detail "on" or "around" or "between" tones which makes the stereo illusion more believable. It gives our ear/brain more data to process. Imaging more precise than a real venue's compensates for playback's lack of actual visual data. On one level, it's a hyper realistic aspect. On another, it fills in gaps to approximate greater sensory wholeness. And the best hifi is always about less facsimilitude and—having played classical clarinet in orchestral and chamber music settings, I cannot invoke realism—more persuasiveness. If we can give ourselves over to the playback experience with less effort and more emotional scope to be played upon... then a hifi has done its strange job to perfection.

The thinking reader already made another connection. Wouldn't a more "light-filled filigreed quality" and "higher treble energy" equate to greater potential for leanness? Absolutely. The Adagio is no compensator for missing beef between amp and speaker. Injecting more body, weightiness or even dynamics often falls on an active preamplifier with voltage gain which otherwise has outlived its needfulness on raw functionality in most modern systems. Should you elect to mate dry class D amps to dry hard-cone boxes, you could well hunger for some sauce. And that wouldn't be part of the Adagio's playbook. On that score, it's a device for mature systems whose only improvable aspect remains the desire for ever higher resolution. All the other aspects are handled to full satisfaction already. Thus Adagio + nCore monos + Aptica = surprisingly good but not as complete and filled out as replacing class D with premium class A. At the time of the Adagio's stay, I also had on hand a tubed preamp and power amp. Despite bona fide excellence in their class, Adagio-direct into the Pass amp operated on a higher level of sensory wholeness. Though pleasing and perfectly lovely and dynamically very well hung, thermionic texturing and thickening closed off fine layers of spatial context and tonal verisimilitude. My tastes and ears didn't need that form of additive repair work. But the proviso is clear: the Adagio isn't a corrector of downstream flaws. It's a revealer of minutiae, thus a critic.

Here it really doesn't replace a traditional active preamp. Instead think of the Adagio as a top-shelf DAC run into a premium passive preamp. Now eliminate common losses from one more interlink cable and connector junctions on either end. Then eliminate losses from variable output impedance, hence suboptimal drive across long cables. In my setup, the Adagio drove 6-metre interconnects without any fuss. Now we have the overall picture to investigate whether an activated passive of Wyred4Sound STP-SE Stage II calibre can improve anything over the Adagio in amp-direct mode; how the Adagio's volume implementation compares to a traditional analog solution as used in the COS Engineering DAC/pre; and finally, how the Adagio's R2R solution in fixed output compares to the discrete R2R ladders of the Aqua Formula.

Adagio and STP SE Stage II conveniently stack for easy cable swaps. Both drove the Pass Labs XA30.8 via XLR for a fully balanced signal path.

Direct or pre? Clearly, Adagio solo produced more sparkle, energy and spatial frisson. By that I mean the peculiar but tacit quality whereby sounds peel out or pop more as though they shed some subtle sheath and suddenly stood naked. With the preamp inserted, the sound got heavier and thicker; clothed in something thin but still something. Whilst some might call said heaviness better/richer, even they wouldn't argue that the associated thickening didn't also take away some immediacy, airiness and charge. Given how the Adagio --> XA-30.8 --> Aptica chain was ideally weighted on tone and substance, I preferred its higher lucidity and micro resolution. With a system in need of more body, I'd just as decisively favour the preamp's gravitational contribution.

Those fond of symphonic crescendi that culminate in thunder, lightning and intense pathos, the preamp's minor fattening and downward anchoring would play well dynamically and on scaling up sheer mass. Those more keyed into exploring soundstaging, going walkabout in recorded spaces and climbing overtone ladders would favour the fully exploded lighting, transparency and shininess of direct mode. By contrast, the preamp played it a tad dull or matte. Some might translate that as a skoch of warmth. Whatever you call it, it came at a cost to the spark of liveliness. To tap that energy uncut relied on eliminating the preamp and its added cabling; if one has a system that delights in such unadorned scrutiny and intimacy.