May 2005

darTZeel NHB-108 Model One Stereo Amplifier

by Jeff Fritz

Review Summary Sound "Silky smooth in every respect" and "able to reproduce each instrument cleanly and within its own space ." "I never got the sense that the NHB-108 Model One was controlling my speakers with an iron fist," but "the darTZeel amp didn’t force the music…. In its relaxed, laid-back way [it] kept my foot tapping." "Through the NHB-108 Model One, listening was a much more intimate experience than simply hearing the sound would have been." Features "One hundred watts per channel into 8 ohms (160W into 4 ohms) are specified, which includes a small percentage of class-A power. Other design details include the use of only very small amounts of local feedback and no global negative feedback." "Four interior compartments are visible through the top panel. The front two each house a 300VA transformer, while the rear two each contain six large filter capacitors for a rated 230 joules of energy storage per channel -- the NHB-108 Model One is a dual-mono design." Use "darTZeel makes it clear that you must have all of your cables -- both to the speakers and to the preamp -- connected before powering on the NHB-108 Model One." Value "When considered against its current competition, the darTZeel NHB-108 Model One simply costs too much money for what it offers."

I’ll spare you the Swiss-watch comparisons. I’ve used them before, and you’ve read similar in other places, so I think we all know the drill by now. The darTZeel NHB-108 Model One ($18,181 USD) hails from Switzerland, the land of great chocolate and, yes, fine watches, and it was created with the same apparent tender loving care as better examples of those two national treasures.

The seeds of the NHB-108 Model One (NHB stands for "never heard before") can be traced back to 1984, when engineering student Hervé Delétraz designed an innovative device -- a digital amplifier with no negative feedback -- as a school project. The sonic performance of that early amplifier began a quest for Delétraz that has resulted in the amplifier you’re preparing to read about. Through much of the ‘90s the actual circuit for what would become the all-analog NHB-108 Model One was under development. According to darTZeel’s "Audiophile Technical Manual" (available for download on the darTZeel website), on November 11 of 1999 the very first NHB-108 Model One was assembled. The current iteration of the NHB-108 Model One has been available in production form since 2002.

Design

According to darTZeel, the NHB-108 Model One (17 1/4"W x 6 3/4"H x 13 1/5"D and 65 pounds) is the product of three overriding criteria: simplicity, purity, and reliability. Although these intents may seem mundane ruminations at first, the thought of a component that succeeds equally at all three is compelling. Those three objectives incorporate much of what is sought after by audiophiles. To attain those in the context of a single product is a noble goal for a manufacturer.

When you unbox an NHB-108 Model One you will feel compelled to gaze at its form. The NHB-108 appears anything but simple. The anodized-aluminum faceplate is gold-colored with right and left "Eyes" that glow orange. If the eyes are "open" the unit is powered on. A central "Power Nose" serves as the on/off switch. Rack-mount ears -- er, handles -- are located to the far right and left of the faceplate and are moderately proportioned but very functional. In the upper left-hand corner is a rectangular recess that is, upon purchase, fitted with a custom-engraved logo bearing the owner’s name. The top panel is a smoked-glass pane that allows you to peer into the extremely well-organized interior. There are no vents in this glass top panel, making the interior virtually dust-proof (what a welcome design detail that is). The heat sinks are red. Yes, red. You may like the look, you may not, but the heat sinks are one of the defining elements in the visual character of the NHB-108. The back panel is gold, to match the front, and also contains small handles. The look is a bit whimsical, certainly not the stoic form often associated with high-end electronics.

The back panel is fitted with XLR inputs, RCA inputs, and Zeel inputs. The latter are BNC connectors that darTZeel plans to use to interface the NHB-108 Model One with a pending preamplifier. According to darTZeel, the Zeels are ideal for transmitting electrical signals (the "Audiophile’s Technical Manual" goes into detail about this design feature). An IEC socket is available for detachable power cords. Befitting an amplifier of this pedigree, nice gold-plated five-way WBT binding posts, one set per channel, are included as well. The NHB-108 rests upon three rubber-bottomed feet.

Four interior compartments are visible through the top panel. The front two each house a 300VA transformer, while the rear two each contain six large filter capacitors for a rated 230 joules of energy storage per channel -- the NHB-108 Model One is a dual-mono design. The capacitor banks sport another of the defining visual elements of the design, namely crescent-shaped polished brass bus bars that couple the caps. The output stage features some atypical thinking as well. One pair of bipolar output devices are employed per channel instead of the multiple parallel pairs that are commonly seen in expensive solid-state designs. According to darTZeel, this simplification is done to minimize signal-path length, lower output impedance, and obviate the needs for massive heat dissipation and precise component matching.

The specifications given for the NHB-108 are also atypical for an 18-large solid-state stereo amplifier. One hundred watts per channel into 8 ohms (160W into 4 ohms) are specified, which includes a small percentage of class-A power. Other design details include the use of only very small amounts of local feedback and no global negative feedback. The very wide bandwidth is specified as 1Hz-1MHz, +0/-6dB. darTZeel’s technical papers go into great detail about distortion products and how the NHB-108 Model One measures. Delétraz goes to lengths to explain that temporal distortion (another name for transient intermodulation distortion, according to darTZeel) is the cause of much sonic woe, and, of course, the NHB-108 has scant amounts of it. The Crowbar protection circuitry guards your investment from several potentially damaging conditions such as excessive output current and voltage drift.

Matching your loudspeaker’s impedance to the NHB-108 is critical, and the NHB-108 comes with facilities under the top plate to adjust for this. For speakers with impedances over 4 ohms, choose the default Hi position, and for under 4 ohms, choose the Lo position. The nominal impedance of my Wilson Audio Alexandria X-2 speakers is 8 ohms, so I used the amp on Hi.

System

I used the NHB-108 Model One in a system well detailed in my "The World’s Best Audio System" column on Ultra Audio. A Boulder 1010 preamplifier was fed signals from either an Esoteric DV-50 universal audio/video player or the $63,000 combination comprising Esoteric’s P-01 transport, two D-01 mono DACs, and a G-0s master clock. Speakers were the Wilson Audio Specialties Alexandria X-2s, and cabling consisted of Shunyata Research’s brand-new Orion speaker cables and Antares interconnects. Power-filtration duties for the preamp and digital front-end were handled by either an Audience adeptResponse or a Shunyata Hydra Model-8 and the accompanying companies’ power cords.

darTZeel makes it clear that you must have all of your cables -- both to the speakers and to the preamp -- connected before powering on the NHB-108 Model One. Read the owner’s manual and you’ll never forget this instruction.

Music

Positively seductive. I remember one of my first instances of hearing the Wilson WATT/Puppy loudspeakers. The gentleman demonstrating them for me said, "You just have to hear how these sound playing back stringed instruments." He was right. The same can be said of the NHB-108 Model One. Listen to Guitar Heroes from the Los Angeles Guitar Quintet [Telarc SACD-60598] and hear how beautifully the NHB-108 captures the essence of the playing. You’ll feel the ebb and flow of Pat Metheny’s "Letter From Home" as if you were amongst the performers. Through the NHB-108 Model One, listening was a much more intimate experience than simply hearing the sound would have been. I was drawn into the setting, not reminded that it was a recording by any error on the amp’s part. The noise floor was low and the air around the individual players was quite high. This amplifier was brilliant with small-scale acoustic music such as this. I just couldn’t find fault playing back this recording.

A Chesky release from the band Oregon, Beyond Words [Chesky SACD252] combines electronic elements such as synthesizer with piano and classical, 12-string, and bass guitars -- among other instruments. The simple arrangement is beautifully captured in David Chesky’s signature minimalist style. "The Silence of a Candle" interweaves the piano and an English horn along with a bass. The frequency band is spanned by this track in such a way that any spotlighting or discontinuities in any particular area would be clearly audible. The darTZeel amp sounded silky smooth in every respect and was able to reproduce each instrument cleanly and within its own space, yet I heard the performance as one event, cut from one cloth, as they say. Especially on small-scale arrangements, this combination of qualities can produce magic.

The bass was bouncy and rhythmic. I never got the sense that the NHB-108 Model One was controlling my speakers with an iron fist; in fact, the bass was more edge-of-your-seat thrilling, as if the NHB-108 was on the verge of losing control without ever following through with the threat. The NHB-108 Model One did not regiment the music -- a good thing with many recordings -- but let it flow from the speakers with ease and abandon. This amplifier will not give the sense of extending your speakers’ bass response. Buy a Krell for that effect. It works. This amplifier simply does not produce that kind of extreme low-frequency drive. What it will do is issue forth the bass spectrum in a wholly organic, natural way. Steely Dan’s Everything Must Go [Reprise 48435-9] is chock-full of energy, rhythmic playing, and tonal color. The darTZeel amp didn’t force the music, but in its relaxed, laid-back way kept my foot tapping.

The late Jeff Buckley’s "Last Goodbye" (Grace [Columbia 57528 CK57528]) captures the essence of the artist in a fitting manner. He sounds a bit distant and thin, but he lets go of the notes with incredible feeling and heartfelt longing. Through the darTZeel amp, all of these elements were communicated clearly. His voice was perhaps lacking that last ounce of body -- as was the lower midrange/upper bass -- which I’ve heard produced by a handful of other amplifiers. But this is getting really picky. I certainly was able to lose myself in the music. The more intimate "Hallelujah" sounded nuanced and gentle, just as I’m used to hearing it, with excellent retrieval of low-level detail.

Metallica’s "Nothing Else Matters" from the Black Album [CD, Elektra 9 61113-2] had good definition and bite. However, the last bit of weight from the Lars Ulrich’s kickdrum was missing. I couldn’t quite get the fist-in-the-sternum effect that this track delivers at full bore. On the positive side, the darTZeel amp did play at surprisingly loud levels -- the sort I could only reach with our four-month old out of the house with my wife.

The darTZeel NHB-108 Model One is certainly an inspired design, and I can say with complete conviction that the music it made was always enjoyable to hear. However, its price is considerable -- even among top-of-the-line amplifiers from well-known makers. Therefore, its ultimate value is defined by other amplifiers -- by its peers, both in the same price range and below -- as much as by its own intrinsic performance. No audio product exists in a vacuum, and this is especially true for a stereo amplifier whose price approaches twenty grand.

Peer pressure

The NHB-108 Model One handily outclassed the Classé Audio Delta CA-2200 ($5000) and Accustic Arts Amp II-ACHP ($10,500). Both of those units impressed me -- the Classé garnered a Reviewers’ Choice nod because, at its list price, it’s an absolute steal -- but neither were able to fully convey the fine textures of stringed instruments the way the NHB-108 could. Neither matched the darTZeel’s ability to deliver perfectly integrated high-frequency texture, either. The NHB-108 was more refined and made the rough edges of these amplifiers apparent, such was its silky smoothness. Both the Classé and the Accustic Arts amplifiers sounded easily as powerful as the darTZeel, perhaps more so, but then again the NHB-108 Model One is not about unlimited power. Its power is refined in a way that leaves the other two contenders needing polish.

The hybrid Lamm M1.2 Reference mono amplifiers ($19,590) were a different story altogether. They captured music with equal beauty, providing a dead-neutral midrange situated within a perfectly woven musical cloth. Top to bottom, the Lamm amplifiers sound almost like nothing at all. And their power rating (110W) doesn’t begin to hint at the outstanding control and dynamic ease they possess. In this regard they deliver more than the darTZeel. Plus, for your nearly $20k, you get monoblocks instead of simply dual mono. Perhaps that’s important to you. The NHB-108 Model One portrays a slightly less-dimensional soundstage and does sound a bit less powerful overall. The NHB-108 does counter effectively with greater air around stringed instruments.

In the stereo realm, the Boulder 1060 stereo amplifier ($20,750) is almost impossible to fault, either sonically or considering its exemplary build quality. With an extremely natural presentation and gobs of power (300Wpc), it strikes me as almost the ideal amplifier. Its robust-yet-ultra-precise construction is a sight to behold, its incredibly quiet mechanical performance inspires confidence, and its vanishingly low noise floor is sheer perfection when coupled with its absolute retrieval of low-level detail. The darTZeel can’t match the drive, the control, or dead-neutral demeanor of the Boulder. The NHB-108 Model One does, however, have a laid-back quality that is perhaps more intimate with some small-scale music than the Boulder is. But at the end of the day the 1060 drives my Wilson Audio speakers with so much ease and finesse that listening is always a pleasure no matter the style of music I choose.

Blame the weak dollar, blame the high cost of Swiss goods in general, blame whoever or whatever you like. Against the amplifiers it will have to battle for your hard-earned dollar the NHB-108 Model One doesn’t quite measure up. I can think of several similarly priced amplifiers I know I’d buy before this one, including the Lamm M1.2 Reference monoblocks and the Boulder 1060 stereo amplifier. If you are about to put down $18,181 for the NHB-108 Model One, make sure you've heard the Lamm and Boulder amps along with contenders from other makers.

Summation

There's a lot to like about the darTZeel NHB-108 Model One amplifier. It shined with smaller-scale recordings, and it sounded silky and refined with whatever music I threw at it. Music flowed through it. In fact, had I not heard amplifiers like the Boulder 1060 and Lamm M1.2 References, I could perhaps end my review there. But those luminaries stand fast at the super-amp threshold. They’re essentially beyond reproach and surpass the darTZeel amp in some important areas, including ultimate authority and overall sonic acuity.

I wish Hervé Delétraz and the folks at darTZeel all the success in the world. They’ve made a fine product, probably the first of many, including some, I am sure, that will cost less and still take advantage of the design work done thus far. However, when considered against its current competition, the darTZeel NHB-108 Model One simply costs too much money for what it offers.

...Jeff Fritz
jeff@soundstage.com

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