Tube Preamp Reviews

For my audition, I substituted the Leto Ultra II for my reference Shindo Allegro preamp, feeding my Shindo Haut-Brion power amplifier with Shindo interconnects. A 6' pair of Auditorium 23 speaker cables carried the signal from the Haut-Brion to my DeVore Fidelity O/93 loudspeakers. The main source was my EMT TSD 15 N Super Fineline stereo cartridge, attached to my Kuzma 4Point tonearm, mounted to my Kuzma Stabi R turntable, which sat atop the Kuzma Platis 65 isolation platform. For digital, I used the Denafrips Ares II DAC, which Herb Reichert reviewed in the November 2020 issue of Stereophile. A 3.6m run of Furutech GT2 Pro USB cable connected my PC to the USB port of the Denafrips DAC. All this gear (except the speakers) was housed in my Salamander five-tier rack. I plugged the Leto Ultra II into my IsoTek EVO3 Aquarius line conditioner.

One fine summer day in the mid-2000s, while hanging with my hi-fi running buddies Michael Lavorgna (now editor of Twittering Machines), Jules Coleman (former 6Moons.com contributor and a professor of philosophy at Yale Law School), John DeVore of DeVore Fidelity, and Tone Imports' majordomo Jonathan Halpern, we headed to a downtown loft where Halpern had assembled a rig comprised almost entirely of Shindo Laboratory equipment: a Shindo-modified Garrard 301 turntable with Shindo-modified Ortofon SPU cartridge; Auditorium 23 T1 step-up transformer; Shindo Giscours preamp, Shindo WE300B Limited amps, and Shindo Latour speakers supported on a platform of rare tonewoods sourced for a rack.

This all-Shindo rig was a game-changing experience for me. I'd never heard such beautiful tonality, natural drive, textural authenticity, and palpable immediacy from a hi-fi system. Later, I'd head to Halpern's home, where he played classical LPs on an EMT 927 turntable, with Shindo separates. Each recording immersed me in effortless dynamics, tangible textures, and rich tone. I purchased the Shindo Allegro dual-mono preamplifiers and Haut-Brion stereo power amplifier, and they remain my reference components (footnote 2).

Them's my tastes, my biases. Keep them in mind as you read.

Listening
The Zesto Audio Leto Ultra II preamplifier is one of very few preamps I've had in house that in some ways equaled my Shindo Allegro—indeed, in some ways surpassed it. The two amps are cut from different sonic cloth, with dissimilar origins, but both are capable of propulsive drive, excellent imaging, and musical realism.

The Shindo is the tone king, with superb immediacy and tactility, producing music that just always seems right. The more modern-sounding Leto Ultra II offered superior transparency and resolution, blacker backgrounds (after flipping the dual ground switches to remove some hum), impressive microdetail, and knockout clarity. The Leto Ultra II presented livelier music; the Shindo was lusher, with more tonal color, midrange-focused mien and presence, with a darker demeanor. The Zesto seemed to propel music more forcefully as I raised the volume via its palm-sized remote. The Zesto was perpetually clear, light-filled, dancing. I could happily live with either preamp.

Record after record, the Leto Ultra II's neutrality, transparency, and recovery of the last iota of sustain gave fresh insight into familiar recordings. Though it lacked the ultimate warmth and liquidity of my Shindo gear, the Zesto did its part to produce a large soundstage with good imaging, first-rate resolution, and focus.

At first, I was wary of the Presence option; it seemed like a gimmick. Maybe so, but if so it's a useful gimmick: Dialing it in two clicks (–2) benefitted some 1970s recordings with especially nasty treble. On prog-rock quartet U.K.'s eponymous 1978 debut (LP, Polydor 6146), Bill Bruford's splashy cymbals and pinched-sounding hi-hats grate like sandpaper; those two Presence clicks smoothed it out. I bought the late Art Dudley's copy of the Faces' A Nod Is As Good As A Wink... (LP, Warner Bros 2574), which didn't need treble-taming as much as U.K. but benefitted from it anyway: Adjusting the Presence control by two clicks made the music more musical and listenable without removing anything essential; it could also reduce surface noise on noisy LPs. More than two clicks, and the music lost some vibrancy and sparkle, two key traits that make the Leto Ultra II so much fun. Still, the Presence control is a useful option that cured the hashiness of some older recordings (footnote 3).

Moving beyond the Presence control and continuing on with vinyl, Sonny Rollins's epic Volume 1 (LP, Blue Note BLP 1542) blasted sweetly through the Zesto. Rollins's tenor was dead-center—it's in mono—grand, and airy, carved in space, the Zesto's high-rez, midrange-to-treble illumination making the performance communicative and joyous.

Returning after my review of the Cambridge Audio CXA81 integrated amplifier to the remastered version of Radiohead's OK Computer, 2017's OKNOTOK (3LP, XL Recordings XLLP868), the new disc(s) sounded cleaner, without the distorted climaxes of the original LP. The Zesto played "The Tourist" with increased bass weight, more nuanced layering of Thom Yorke's vocal harmonies, and better realization of instrumental lines in recorded space. Greater texture from vocals, drums, guitar, and keyboards gave increased insight to this landmark rock disc. Though the Zesto's portrayal was slightly less enveloping than that of the Shindo, its greater resolution, clarity, and note sustain were irresistible.

Similarly, the Zesto lacked the first-row presence of the Shindo when playing saxophonist Steve Coleman's trio outing Triplicate (LP, ECM 1373) with bassist Dave Holland and drummer Jack DeJohnette, but it resolved the character of the performance in more detail, with more air on drums and a tighter grip on acoustic bass notes. It performed a similar feat on Frank Sinatra's 1954 release, Swing Easy! (mono LP, Capitol W-587), every instrument focused, the master's voice big and well-defined.

The Leto corroborated my preference for original pressings and early reissues of jazz LPs—rarer and more expensive though they may be—over their modern, high-rez counterparts. Through the Leto Ultra II, the soaring, nasal notes of John Coltrane's tenor on Traneing In (1958 mono LP, Prestige 7123) echoed off the walls of Rudy Van Gelder's Englewood Cliffs studio, supported by Art Taylor's perky ride cymbal and Paul Chambers's resonant, deep-throated acoustic bass. Classical LPs were also reanimated—or perhaps I should say that their life was not obscured—via the Zesto, including the grand, brilliant piano of Vladimir Horowitz on The Studio Recordings New York 1985 (stereo LP, Deutsche Grammophon 419 217-1), the purity and refinement of André Previn's London Symphony Orchestra in a concert performance of Ravel's opera L'Enfant et les Sortilèges (1982 LP, Angel Records DS-37869), and the tonal clarity and beauty of Karl Böhm conducting Tristan und Isolde at Bayreuther Festspiele 1966 (1968 LP, Deutsche Grammophon 136 433). The Zesto's refined, neutral character, apparent low noise floor, big soundstage, and clarity made the most of these and other classical recordings.

I was less thrilled with music streamed from Tidal and Roon. It's hard to blame the Leto for that when it sounded so good with other sources. Perhaps the Zesto's transparency exposed a certain sameness to the sound of streaming, even when using the Denafrips Ares II DAC, regardless of genre or era.

Conclusion
When your reference preamplifier regularly bests all comers, ticking off the reasons why lesser equipment can't compete becomes commonplace. The Zesto Audio Leto Ultra II preamplifier was a welcome deviation from that pattern. It blew out my preconceptions and expectations. For textural viscosity, tonal purity, first-row presence and overall naturalness, it couldn't quite match my Shindo Laboratory Allegro preamp—chosen precisely because Shindo is the best in those respects—but it brought its own important virtues. Superbly clean and transparent, the Leto Ultra II's midrange-to–upper treble focus and lucidity was off the charts, giving fresh insight to familiar LPs. Silky and smooth, its tone was also good. With its user-friendly, logical options, the Leto Ultra II is among the very best line preamplifiers I've heard, and it comes with a useful, innovative, fully defeatable tone control (the Presence feature), wrapped in an unusual, cosmetically striking frame.

Must be heard to be fully appreciated. Highly recommended.

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Footnote 2: That's a slight oversimplification. Art Dudley and I both had Haut-Brion amps, but they were different versions. (Shindo designs sometimes change over time.) I preferred his, he preferred mine, and so, a couple of years ago, we traded Haut-Brions.

Footnote 3: Having had a good, long listen to the Leto model that preceded the power-supply upgrade at the Toronto Audio Fest, I would argue that the Presence control is good for taking the edge off some more recent recordings, too. And when it isn't needed, it's completely bypassed, so it does no harm. I'm happy to see this rigorous rethinking of the traditional tone control.—Editor