Solid State Power Amp Reviews

Midmorning of day five of the break-in period, I took my first critical listen; I chose a jazz selection from pianist Cyrus Chestnut's debut album, Revelation (16/44.1 FLAC, Atlantic Jazz 82518-2). This is a trio date, and on the closing track, "Cornbread Pudding," you're witness to incredible interplay between Chestnut, bassist Christopher Thomas, and drummer Clarence Penn. The session was engineered by Jim Anderson and mastered by Joe Gastwirt, and the realism of the instruments and the solid presence of the players in the soundfield has made this disc one of my reference evaluation tools for many years. Midway through the track, there's a great acoustic bass solo by Thomas; on a first-class system, you get a really good sense of the woodiness of the plucked bass and its incredible depth. It's a really good tool for assessing a speaker system's ability to portray bass and midbass content accurately: I know this record thoroughly.

I was struck by several things almost simultaneously. Image specificity seemed greatly improved with the Bel Canto e1X; it became easier to identify the positions of each player in the soundfield. As drummer Clarence Penn pounded the skins and tapped the cymbals, it was much easier to aurally "see" the placement of the tom-tom and kickdrum; his rapid-fire snare and cymbal work blazed across the middle of the soundstage. Chestnut's pianism flowed from the LRS loudspeakers more fluidly and with a greater sense of ease. And Christopher Thomas's bass fairly jumped out of the speakers. The overall tonal palette of the performance went from exceptionally good with my Emotiva amps to, well, almost Technicolor through the e1X.

And the e1X exerted a level of control over the Maggies that I'd never before experienced. Magneplanars—especially the smaller ones—are notorious for exhibiting some degree of mid-bass panel flap: Magneplanar bass panels are riveted at a number of points to control excessive panel flexure, which also restricts the panel's free movement when relatively strong bass content is present. Lesser amplifiers will allow enough panel movement to cause a relatively loud "thunk" around the rivet location; I've heard this countless times with almost every pair of Maggies I've ever owned—and it can be particularly obvious with plucked acoustic bass content. (Think: Jimmy Garrison's powerful acoustic bass solo on "Lonnie's Lament" from John Coltrane's classic Crescent [16/44.1 FLAC, Impulse 1764902].) No matter how close to or beyond reference levels I pushed the e1X-driven LRSs, they responded with absolute authority and zero driver-induced distortion.

The Bel Canto e1X was undoubtedly also the quietest amplifier I've ever had in my system. With the LRS speakers being so very inefficient, you generally need to really crank the volume knob to get to SPLs approaching normal levels. Full-blown orchestral passages from sources with tremendous dynamic range require an even further twist; it's not unusual for the volume on my PS Audio preamp to reach 80 or 85 on a scale that maxes at 100. With every other amp I've used in my system, I could always hear some residual noise in the background, even with the most well-engineered recordings. Not so with the e1X—nothing, not a peep: It was absolutely, perfectly, completely silent.

Listening with the Zu Audio Omens
Zu's loudspeaker designs (footnote 1) are almost all based on a single 10" (approximate) full-range driver that's adapted from a Harry Olsen design from the 1930s (footnote 2). That driver is then augmented by a compression tweeter loaded with a shallow aluminum horn; a single, high-quality capacitor placed ahead of the tweeter forms the high-pass filter. The Omen ($2250/pair) is rated at 12 ohms, with a sensitivity of 95dB. I regard the Omen as one of the best bargains currently available in high-end audio.

After days of marveling at the Bel Canto amp's interaction with the Magneplanar LRS, it was time to swap in the Zu Omens, to see how well the e1X addressed the peculiarities of a high-efficiency design. I've found that lower-quality amps can assign a certain "chestiness" to the Zu's full-range driver, often accompanied by a slight increase in grain in the treble coming from the compression tweeter. I chose the track "Drown in My Own Tears" from Soul Serenade (16/44.1 FLAC, Columbia 89013), a 2003 release from the Derek Trucks Band that features Gregg Allman on lead vocals. The song begins with a searing slide guitar intro by Trucks, with Hammond organ accompaniment, then segues into Gregg Allman's whiskey-drenched vocal—minus some of the rawness of tone from three decades earlier with the Allman Brothers Band, although on this 2003 release it nonetheless retains all of its power and effectiveness. With the Bel Canto, that chestiness was gone.

I followed this with a track from DTB's next album, Joyful Noise (16/44.1 FLAC, Columbia 86507), "Baby You're Right," which features a stunning, blues-drenched love call from Susan Tedeschi, the future Mrs. Trucks. Tedeschi's gut-wrenching vocal delivery is matched only by the intensity of Trucks's astonishing slide guitar technique—Duane Allman would have been impressed! When she shouts out, "I wanna love you, I wanna hug you!," you'd believe it (obviously Derek Trucks did, too). With the e1X in the system, this music sounded even less compressed, and the Omens remained perfectly mannered while delivering a brute assault on the senses. The apparent clarity of the e1X made it easy to appreciate the strengths of the Omens, which are good at portraying the dynamics of jazz and orchestral music but can also rock with the very best. They can't match the hyper-holographic spatial performance of the Magnepan LRS, but they definitely imbue Gregg Allman's growl with a certain rightness that the LRS misses.

Conclusions
I admit some expectation bias: I would have expected a high-end stereo amplifier with a $6000 price to outperform my $1600/pair Emotiva monoblocks. But I wasn't expecting the e1X to be this much of an improvement. I didn't expect to be so completely gobsmacked by the level of clarity and musicality I'm hearing now from the e1X, with both the Magnepan LRS's and the Zu Omens.

I'm smitten with the wide and deep soundstage that I get from my Magneplanar LRS loudspeakers and how they disappear before me. And I love the muscularity and purity of tone that I get from my Zu Omens. And now, here's an impeccably musical amp that makes it easy to have both.

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Footnote 1: Stereophile hasn't reviewed the Zu Omen but has reviewed the conceptually similar Zu Essence and Zu Soul Supreme.—Ed.

Footnote 2: Harry F. Olsen was a prominent engineer at RCA Victor and an early pioneer in the field of acoustical engineering.