Tube Preamp Reviews

On the outside, the Zesto Leto Ultra II line preamplifier ($10,900), which Ken Micallef reviewed earlier this year, looks a bit different than most other audio components. The designs on its faceplate resemble ocean waves. Waves are also evoked by the bending mirrored plate above, which obscures transformers and other electronics and, in dim light, reflects the Leto's gently glowing 12AU7 and 12DW7 tubes. Otherwise, the Leto's only important features are three front-panel knobs: one for volume, one for source selection—and a third that Zesto calls its "presence control."

The presence control is a tone control with a very specific purpose: to tame the high end on especially rowdy recordings. Based on my first exposure at the Toronto Audio Fest, Ken's listening, and JA's measurements, it seems to be well-executed. So, after Ken completed his review, I asked if I could hang on to the Leto for a while.

John Atkinson's measurements show exactly how the presence control works (fig.1). When the presence control isn't engaged, the Leto rolls off the high end very slightly, specifics depending on the load and whether the balanced or unbalanced outputs are in use. Setting it to –1 rolls the music off slowly starting at about 1.5kHz, reaching –2dB at 10kHz and –5dB at 20kHz. The next setting, –2, has a knee frequency at about 1kHz, reaching –3dB at 10kHz and –6dB at 20kHz.

The –2 setting is interesting because it's so close to –1; indeed, it isn't easy to hear the difference on most music. It's as if George Counnas, the Leto Ultra II's electronics designer—Carolyn, George's wife and partner, is responsible for the industrial design—decided there was too big a difference between two adjacent settings in the most important region and decided to add another one in between, one that's only slightly more aggressive than –1.

Time to try it out. I plugged the Leto in, connected it up, put on some music, and went off to have lunch while it warmed up. An hour or so later, I judged we were both ready for some music.

Looking at new music in Roon, I immediately noticed the recent CSN&Y Déjà Vu reissue courtesy of Qobuz (24/96 FLAC; there's also an MQA version on Tidal, and I listened to both). I adjusted the volume to a comfortable level and started playing with the presence control just to get a feel for it.

My first thought was: No one would ever use the most aggressive setting; it severely suppresses highs and even mids. My second thought was, well, maybe with very bass-deficient speakers, this could serve as effectively a bass boost, although it would be boosting the lower mids as well. I don't have any bass-deficient speakers here—the Wilson Alexx Vs that I have in for review certainly don't qualify—so I couldn't try it.

The second highest setting (–4) is also very aggressive, but it retains enough treble to be useful. Indeed, this setting's most important qualitative effect was to accentuate the bass. (It's all relative, after all.) It did change the timbre of some instruments and voices (including Stephen Stills's), but not as much as you'd think.

What's really useful here, though, are the top three settings, or maybe the top four.

Surprise: I found I enjoyed –2 or even –3 on several songs on the new reissue of Déjà Vu—the digital, streaming version, whether MQA on Tidal or regular high-rez FLAC on Qobuz. There's a roughness to the highs on some of these tracks—"Everybody I Love You," the last track before the demos kick in, is one—that benefits from a little high-end suppression. Certain moments in "Carry On" benefited, although not as much as "Everybody I Love You."

What genre is Carolyn Shaw's new album, Let the Soil Play Its Simple Part, with So Percussion? Considering the artists involved, this must be contemporary classical. Shaw, after all, won the 2013 Pulitzer Prize for Partita for 8 Voices, written for her ensemble Roomful of Teeth. She has also written music for Renée Fleming, the Seattle Symphony, the LA Philharmonic, and many other obviously classical musicians and ensembles.

And yet, stylistically, this album bears a resemblance to music by Joanna Newsom, who, despite classical training or perhaps because of it, in 2015 found herself perched atop Billboard 's "Alternative Albums" chart. (She topped the "Folk Albums" chart, too, at the same time.) If Newsom could accomplish that, there's no reason this album from Carolyn Shaw couldn't, too. Add a few guitar solos and it would sound like Radiohead. (I just noticed: Roon tagged Soil as "Alternative/Indie Rock" and "Pop/ Rock" alongside "Classical" and "Vocal Music." Good for them.)

I've written it before but not often enough: We're living in a golden era for what used to be called crossover music. Many young, talented musicians, full of enthusiasm and with sufficient musical chops to play anything, are disrespecting boundaries and allowing themselves to be influenced by anything and everything without respect for genre. I used to despise crossover because it always seemed patronizing, but it isn't now.

Shaw's album is gorgeously recorded and needs no presence-control taming—and yet I've listened to it twice now, once with the presence control turned off and once with it set to –1, and found I enjoyed it more with the latter setting. At this setting, the effect is very subtle. Consequently, the presence control could be more widely applicable than I assumed it would be.

The White Stripes' White Blood Cells (Deluxe) just appeared (24/44.1 FLAC, Qobuz). Neither remastering nor a few extra bits could take the edge off of this intentionally raw, but very enjoyable, recording. (There's also a 20th-anniversary Lego kit depicting Jack and Meg.) It took the –3 presence-control settings to fully tame the sibilance in Jack White's voice on "Fell in Love with a Girl," although –2 sounded better overall, since –3 took away too much of the guitar's edge. On this album, though, I strongly preferred –2 to 0.

Some say you should review components only with familiar records. There's wisdom in that, but there's a major downside: Neither you nor your readers get to listen to and learn about new music. Who wants to read about the same songs month after month? And yet: Familiar music must be part of the review process; otherwise, your experiment lacks a control, your experience a point of reference.

Fortunately, there's one album I've listened to repeatedly since I discovered it a week or so ago, with my current, familiar reference system, so the music is both new and familiar: Double-bassist Luis Cabrera's Canto Interno on the superb Dutch label TRPTK. I first heard this album last week as a CD-rez promo download. I liked it so much I paid €25 for the DXD download from the TRPTK website (DXD, TRPTK0072—a rare download with an actual catalog number, another thing in this label's favor). The music—a grab bag from Bottesini, Koussevitzky, Schumann, and Franck—is mostly familiar and yet diverting, and this may well be the most natural-sounding chamber music album I've ever heard. Superb.

With the presence control disabled—of course—it sounded gorgeous and natural through the Leto Ultra II. This is a preamp that wears its tubed nature lightly, imparting a slight creaminess on the sound while giving up little in the way of transparency. Instrumental timbres remained natural and soundstage depth was preserved. At anything close to natural listening levels, there was no audible noise. I've emphasized the presence control here because that's what I set out to do, but please don't go away thinking that's the main thing on offer. This is a great preamp, pleasantly and unusually styled, with a useful and unusual feature.—Jim Austin