darTZeel NHB-108 model one stereo amp

Specifications:

Type: Solid-state stereo amplifier
Output power: 100 watts RMS @ 8 ohms, 160 watts RMS @ 4 ohms
Gain: 26 dB @ 8 ohms
Input Impedance: RCA: >100 kohms, 5 Hz to 200 kHz
Output Impedance: < 0.33 ohms, from 20 Hz to 20 kHz
Frequency Response: 10 Hz to 100 kHz, +0, -0.5dB
THD: < 1%, 7 Hz to 77 kHz
Signal to noise: > 105 dB
Serial Number: TZ-UA1081.004
Dimensions: 440mm W X 335mm D X 170mm H
Weight: 30 kg (65 pounds)
Price: $9,898.98 introductory price, soon to be $12,121 because of exchange rates

Distributor Information:
Delétraz Engineering
5, chemin des Halliers
CH-1234 Vessy / Geneve
Switzerland
Telephone: 004122-784.3393
Fax: 004122-784.4394
Email: info@dartzeel.com
Website: http://www.dartzeel.com

This is an interesting amplifier. Hervé Delétraz, the designer and manufacturer of the darTZeel NHB-108, is known to be an unconventional engineer, and this is the singular fruit of his labor over a sixteen-year period in the consumer audio arena. Two lengthy and, at times, quite humorous user manuals are provided. The Owner’s Manual is mandatory reading to learn about features and correct usage. The Audiophile’s technical manual explains the designers’ goals and delves into the theory behind the numerous circuit innovations and design choices. Highlights of these choices include: no DC servo compensation or current limitation, no negative feedback at the outputs, and only two bipolar output devices per channel. This is a purist/minimalist design regarding the integrity of the signal. The designer feels the timing of musical events carried in the virgin signal is a fragile thing, and is easily compromised when circuits are “improved.” A heroic effort is made to avoid this. Beyond those two bipolar output devices nothing touches the signal: all fuses, switches and contacts are outside the signal path.

Fit-n-Finish

The more I look at the darTZeel, the more I appreciate the highly evolved design aesthetic at work. Every detail appears to have been thought out and fitted into the overall idiosyncratic concept, with quality and aesthetics being foremost in mind, rather than an eye on the bottom line. The sensibility at work here reminds me of Italian autos from the ‘50s and ‘60s, with the emphasis on attractive colors, rounded edges, overbuilt engines and a bit of whimsy.

The EYES have it

The face of the NHB-108 is anthropomorphic in a cartoonish way. Aside from the 24k gold-plated Identification Plate on the top left front corner with your name and the serial number engraved on it, there are two large indicator ‘Eyes’, one for each channel, and the push button on/off ‘Power Nose’. Again that sense of humor is at play. Those Eyes tell you a lot about the health of the amp. In normal operation, the Eyes are lit an orangey-red color, which complements the gold chassis nicely. If an Eye blinks at you it probably indicates the presence of stray DC voltage in that channel. Likewise, they’ll start to glow brightly if you crank-up the volume too much and soon activate the protection circuit. On the other hand, if the signal is below a set threshold of 10mW under 8 ohms for 45 seconds the Eyes dim as the amp goes into idle. This happened occasionally while listening to a quiet passage. Then the music gets loud and they instantly go bright. However, this is only a visual cue. There is no change in the amp’s operation and no sonic effect, but I found it a little distracting. I’d say idle mode comes on too quickly, and the signal threshold is set too high. Maybe make idle mode optional, via a switch. The over-sized ‘Power Nose’ operates smoothly and securely, and matches the gold of the chassis.

Around back, there is one set of XLR inputs, one set of RCAs, and one pair of special darTZeel BNC inputs (these are for use with darTZeel cables). The WBT speaker binding posts with clear plastic screw-down locking mechanisms were easy to use and made for secure connection, but they could be bigger to accommodate larger spade lugs. I appreciated the two sets of formidable, matching gold-colored handles, front and back, every time I experimented with a new footer, etc.

Looking down through the smoked-glass top gives an interior view of immaculate build quality. Each amp is handmade, but you’d never know it from its looks. Inside are four quadrants, symmetrically laid out to support the dual-mono design. There is a veritable kaleidoscope of colors, with gold-colored, crescent-shaped, metal bus bars, blue capacitors, red resistors, along with two large transformers. It even coordinates with the exterior gold-colored high quality anodized aluminum chassis and dullish red heatsinks on either side. All those critical parts are decoupled at different frequencies by tuned rubber suspensions.

I situated the NHB-108 on the floor about 2-3 feet away from any other component, a good idea because the amp is not fully shielded. Hervé feels fully shielded systems sound blurred and fuzzy. That is also why a glass cover is used – to allow residual magnetic fields to escape. In operation, the amp itself was totally free of mechanical noises and there was just an average amount of noise from the speakers when there was no signal playing. If noise is a problem, a jumper wire is provided to connect both output speakers’ grounds to kill the residual noise. The amp got barely warm after a few hours of use.

So how does it sound?

Enjoyable and non-fatiguing, tonally well-balanced and warm, satisfying and a bit soft, these are all characteristics of the sound of the darTZeel NHB-108. Another way to put it is that the amp invites you to relax and put your feet up. You’d probably swear there were tubes somewhere, because you won’t hear the usual solid-state artifacts. I was repeatedly amazed that only a small mental shift was necessary when I swapped between the Master Sound 845 SET monos, my reference tube amp, and the NHB-108. It promoted extended listening sessions and so made a mess of my daily schedule.

On source material with difficult treble, like Swingin’ and Burnin’, by the John Cocuzzi Quintet [Wildchild! MS 06652], track two, ‘Broadway’, has a very prominent ride cymbal. Its image is large and forward, and can easily get out of control to the point that it’s all you hear. This never happened with the darTZeel. The treble is present in proportion to the other bands and all of the cymbal’s events were audible and finely differentiated, but it never got in your face. This has to do with the tube-like warmth and sweetness of the highs and lack of hardness or edge. On track three, ‘What Did I Do To Be So Black and Blue?’ a clarinet joins the ensemble. Allan Vaché does not play in a timid manner. His clarinet bursts forth and quickly lets you know about the health of your system’s high frequencies and dynamics. The clarinet’s treble forte can pierce right through you and possibly cause that stunned, glazed over expression you sometimes see audiophiles sporting at listening sessions. These guys are suffering from treble slash and burn. This happened much less with the NHB-108 in the chain, and a footer or wire change was all that was required to take care of it. But even when the treble was piercing, it avoided the grainy break-up and iciness of other amps, and had more of the startle quality of a shout.

The NHB-108 actually does a superb job with Elizabethan viol music. This is a difficult task under the best of circumstances and generally I avoid playing this musical genre with SS amps, the results being less than engaging. It demands convincing string tone, an area that has always been problematic in reproduced sound.

I’m listening to Goe Nightly Cares, music of John Dowland and William Byrd, performed by Fretwork, the pre-eminent viol ensemble [Virgin Veritas CDVB 7243 5 61561 2]. I’m somewhat shocked to find that the NHB-108 manages to pull this off quite acceptably with the correct tonal balance, full overtone complement and the removal of what we commonly call a solid-state signature. I’ve already mentioned the treble. The mid-range comes from the same origins. The NHB-108 has got the sweetest, most naturally detailed mid-range and treble of any SS amp heard hereabouts. I could almost swear I’m hearing that tube byproduct effect of even order harmonics being injected into the mix. This means that string tone on classical music is the best I’ve gotten from solid-state. It also means the NHB-108 deviates from neutral in a euphonic direction, just like many fine tube amps.

By the way, if you like this early music, check out The Spirit Of Gambo, music of Tobias Hume [Glossa GCD 920402], played by the Labyrinto viol quintet. The compositions are equally sophisticated and performed with excellent ensemble playing. This CD has the added thrill of soprano Emma Kirkby on a few tracks. Some people feel her best years are behind her, but on this 1995 recording she’s audibly in very good form. The recording is more closely miked than Goe Nightly Cares and has better sound overall. You can hear the guys grunting and snorting: after all, playing a viol is hard work, no? Our aesthetic sensibilities have traveled far in the 400 years since this music was popular, circa 1600. Today we find its intervals and meters eccentric, unfamiliar and modern sounding. Personally, I find it has an otherworldly, ethereal quality and it transports me to a place far from my usual GPS location.

When I don the critic’s hat, it occurs to me how excellently the NHB-108s treble is integrated with the mid-band, to the extent that you’re not aware of the treble, per se. These two bands blend so harmoniously they seem to be organic.

The bass is proportionally represented and shares the warm, sweet, soft qualities. The NHB-108s 100 watts/channel give you adequate dynamics for most orchestral music. Crescendos come across very well without breakup or strain. Transient performance is also very good. It’s interesting that Hervé managed to get good dynamics and speed yet still keep the overall soft quality. Mind you, it’s not the slam factor or speed of the YBA Passion 1000, my reference for SS slam. The real finesse of the NHB-108 is in its mid-range and treble tonal reproduction. Elizabethan viol music demands excellent string tone, not cutting edge slam and transient speed.

The sound stage has excellent width and depth and is continuous from left to right. There are no artificial holes between instruments and those instruments have soft boundaries. Detail retrieval is high up there, in spite of the soft-edged images. You can discern the hairs on the bow apart from the sound of the instrument, if that’s your thing.

Speakers, wires and tweaks

Relatively simple, 8-ohm load speakers like the EgglestonWorks Rosas and the Kharma Ceramique 3.2 were the best mates for the NHB-108. The Ayon Signatures, a 4-ohm load, also sounded good. 

I found the Von Gaylord Live Performance AC conditioner energized the amp’s performance. The residual grain and edginess were further diminished, instruments put on weight and were fleshed out, and the bass improved. There was more liquidity overall with the Live Performance. However, the NHB-108 was more revealing and gave a bigger soundstage plugged straight into the wall. 

This is one of those components that will appeal to the set-it-and-forget-it audiophile because it’s very easy to setup. I did try several different footers. Best results were achieved placing it on a Mapleshade maple slab, sitting on a set of Mapleshade IsoBlocks, or using the IsoBlocks alone.

The Golden Sound Red power cord lent its usual performance boost. For the most part, Harmonic Tech Magic interconnects and speaker cables were employed.

There’s just that very long break-in time to get through, which I’ve read elsewhere, can extend for a month or two. My unit came from another reviewer and so had plenty of time on it. Initially, it sounded good after a few hours, but a bit closed in. It required a full week of 12-hour days to really open up.

Conclusion

Well, here it is finally, a solid-state amplifier that truly captures that tubey sound.
Such a commingling of qualities, we might have to invent a new category.

The darTZeel NHB-108 possess the best treble of any solid-state amp I’ve encountered. The mid-range is also first rate. I haven’t come across a solid-state amp that does small group classical, acoustic music or jazz combos as well. 

The one thing that does bother me about the darTZeel NHB-108 is the cost. The $9,898.98 introductory price(!), soon to become $12,121, is a lot of cash. However, if you love the sound of tubes but won’t venture there, for whatever reason, the darTZeel NHB-108 is the closest you’re gonna come to filament bliss.

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