darTZeel NHB-468 monoblock power amplifier

What's the point of reviewing a pair of monoblock amplifiers that costs more than most people spend on two or even several cars— and far more than most audiophiles spend on an entire music system? That's a good question. Another is: Why should I write this review when, just seven years ago, I reviewed a pair of darTZeel monoblocks that look exactly like this new pair?

I realize that products such as the darTZeel NHB-468 ($170,000/pair) are for the very few, but the very few include far more people throughout the world than you may realize— people who can afford such costly audio products and who do buy them. I know, because in my travels I've met a lot of them, and they deserve to read reviews of products they're considering buying—things most of us can only dream of owning.

What also makes this product worth reading about is that the man who created it admits to being directed more by sound than by measurements—within the boundaries of competent electronic engineering, of course. That takes him to some unusual, thought-provoking places where the measurements-oriented people often don't go . . .

Description
Last spring, before the High End 2019 show in Munich, I made a side trip to Switzerland to tour darTZeel's factory and machine shop, and to visit the listening room of founder and chief designer Hervé Delétraz. His speakers of choice are Klipschorns: not at all what I was expecting— I'm not sure what I did expect from the man behind this quirky brand—nor was the sound what I thought I'd hear.

In that system, driven by either the darTZeel NHB-108 Model 2 amplifier or the new 468 monoblocks, those corner horns delivered a steady stream of "I've never before heard that!" revelations from every high-resolution file and vinyl record we played. I came away understanding Delétraz's transducer choice. On the other hand, the obviously bumpy frequency balance, lack of deep bass, and "last century" spatial presentation—like listening through an open window—left a great deal to be desired compared to what I hear at home. "You can't have everything—either at home or in the concert hall," I thought while listening at Hervé's, though what these speakers did correctly kept me seated for quite a long time!

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Soon after my return to the US, a pair of NHB-468s arrived at my house. They look very similar to the NHB-458 monoblocks, which I've owned and enjoyed since I reviewed them in 2012, and which I had no desire to replace. As I like to say about my similarly quirky 2008 Saab 9-3 Turbo X, "I'll drive this car to the nursing home!" (hopefully no time soon), and I have felt the same way about the 458s. (Unlike Saab, at least darTZeel is still in business!)

Outwardly, the 468 differs from the 458 only in the richer and more gleaming gold finish on its front panel—that and, on its rear panel, a 20A IEC jack that replaces the 458's 15A one. (According to Delétraz, 458 owners can get the guts upgraded and keep the old chassis.) The new amplifier's operating system, feature set, and front-panel controls and display screen remain unchanged from those of the 458—I describe these in detail in that 2012 review—although much of what's inside (though not all) has been completely redesigned and is very different. The biggest change to the audio circuitry involves a patent-pending technology/circuit design darTZeel calls CP2C, an acronym for Constant Power to Current. According to Delétraz, he and his design team have invented a "physically contradictory" circuit that "mimics a current source with the output impedance of a voltage source." The circuit design is said to deliver appropriate power to the loudspeaker on demand, with the proper speed and timing, while correcting in real time the loudspeaker drivers' counter electromotive force (back EMF).

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The instruction manual avers that the amplifier should not be considered as either a theoretically ideal voltage source or an ideal current source, both of which, in addition to many flaws, have good qualities. To paraphrase the manual's "Franglish," a perfect voltage source has zero output impedance and in practical terms requires 100% negative and global feedback, which produces temporal (phase) distortion. An ideal current source has infinite source impedance, which is good for controlling a speaker's back EMF, but produces poorer measured performance and sound quality that is overly speaker-dependent. The company claims that the CP2C circuit produces an amplifier-to-speaker connection equivalent to the matched impedance links—the 50 ohm "transmission line" Zeel connection—that darTZeel uses between their NHB-18S preamp and its amplifiers.

The amp is biased into class-B "as much as possible," allowing for cooler operation, longer component life, and no negative sonic impact, because darTZeel claims faster rise/fall times than with higher-bias designs, suggesting that class-A is only useful in asymmetrical circuits, not push-pull.

The 468 is rated as outputting 475W RMS (550W peak) into 8 ohms, 625W (700W peak) into 4 ohms, and 222W RMS (300W peak) into 2 ohms. That's bound to raise some eyebrows, especially considering the massive power supply, with 750 joules of available energy. Power measurements for its predecessor, the NHB-458, are 530W into 8 ohms, 800W into 4 ohms, and 1025W into 2 ohms. Note that both amps use the same massive power supply, featuring one of the biggest power transformers I've encountered in an audio product, which floats on a suspended platform that's tuned to absorb frequencies between 40Hz and 70Hz.

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The 468 retains the 458's zero global negative feedback, fully open-loop output stage, which means no output impedance compensation (Zobel network, etc.), so if you accidentally short the amplifier it's likely to blow up in a cloud of smoke. That's the price paid for purity.

According to Delétraz, the NHB-468 can drive "any speaker and you can go down to 1 ohm and even below (and the amp will still produce great, undistorted music)," and he suggests the amp "was not designed for electric welding but for hysteric goose bumping."

More hysteric goose bumping
In my room, driving the Wilson Audio Specialties Alexx speakers, my darTZeel NHB-458 monoblocks were rarely required to produce more than a few watts—although when called on to reproduce some bass-heavy material, and where I wanted it loud, they peaked out at a few hundred watts.

But I prefer having the wattage on reserve for reviewing other speakers. For instance, I was happy to have the added current when I reviewed the Sonus Faber Aidas.

For seven years, the 458s have kept me sonically satisfied. Sure, the recently reviewed CH Precision M1.1 amp, configured as a monoblock pair, definitely produced more bottom-end weight and punch, just as the Ypsilon Hyperion hybrid monoblock amps demonstrated that greater harmonic expression and bloom could be produced in the mids and upper-mids (and being a hybrid design with solid-state output, they were no slouches on bottom). While I wouldn't mind having me some of that, I found more to my liking the rest of what the 458s do.

Then the 468s arrived.

A friend helped me install the new monoblocks, and I ran them with my NHB 18NS preamp for many weeks, using the original darTZeel 50 ohm cables I'd received with the 458s in 2012 (although a new and supposedly improved set of 50 ohm cables came packed with the 468s).

COMPANY INFO
darTZeel Audio SA High End Audio Manufacture
US distributor: Blue Light Audio
2725 SW Sherwood Drive
Portland, OR 97201
(503) 221-0465
ARTICLE CONTENTS

COMMENTS
Bob Loblaw's picture

Oh man are those ugly. The build quality looks incredible, but if there was an award for tackiest gaming PC, these would win it.

Graham Luke's picture

...you're the kind of guy who keeps a Ferrari in the garage, these things make perfect sense, n'est ce pas?

Bogolu Haranath's picture

Spectacle de richesse :-) ........

Long-time listener's picture

They need to stop letting engineers design the boxes...or whatever is producing visually unappealing equipment. Like the ATC P1 amplifier. Or the Cambridge Audio Edge amplifier--please don't put the knob right smack in the middle, and don't give me those broadly rounded edges. Or those wall-eyed Chord DACs. Just give me a clean, rectangular black box and I'll be very happy. And not that eye-piercing silver stuff either...

RH's picture

"They need to stop letting engineers design the boxes...or whatever is producing visually unappealing equipment."

Eye of the beholder.

I'm groovin' with the Iron Man look of those amps. Pretty cool.

JRT's picture

I like the aesthetic of "champagne" dyed anodized aluminum faceplate and rosewood panels. Sadly, the hardware that I want is not dressed like that, and form follows function in the priorities.

wilco's picture

in Audio are all over the map: from boring to ridiculous to just plain ugly.

I actually think the Darts are beautiful.. Maybe bordering on ostentatious, but they do "look" like $175K amps!

The most prominent high end speaker design that I could not stomach be in the company of-- no matter how heavenly they may sound-- are the Wilson Speakers. Robotic, clunky, aggressive-- clearly the work of a design-impaired engineer.

Long-time listener's picture

Butt-ugly. Once, years ago, I heard a pair of them in a showroom. I didn't think they sounded good either.

Bogolu Haranath's picture

Conclusion (or, summing up) ..... MF is gonna upgrade and buy the new darTZeel NHB-468 mono-blocks :-) .......

Bogolu Haranath's picture

'cause ..... there is more there, there :-) ........

tonykaz's picture

just kinda shows that his $1,000,000 system wasn't all that dam good in the first place.

Who will pay for it? we subscribers or the Manufacturer needing some Publicity? and other manufacturers.

We at General Motors regularly supply our "Advocate" Reviewers with Long Term Loaner Cars for their families, we consider the practice pervasive, we would even "help" them write their reviews.

Tony in Venice

Ortofan's picture

... a Toyota made in the previous century instead of a new GM car.

tonykaz's picture

Thanks for the referral, I just had a quick look at one of his "explanations" and was delighted.

His Garage is "FILLED" with hoarding Junk so he must have important opinions on things.

I Subscribed Immediately! ! Scotty will be one of my 121 YouTube Subscriptions of interesting people with things to say and the natural ability to say them. He's Loquacious

And...

You're right, GM would NEVahhhhhh let this guy near any of our New Cars or old ones if we could help it. We have a rather rich field of serious quality gaps that need forgetting.

Since we are talking about GM's embarrassing....

Adios,

Tony in Venice

JRT's picture

(edited toward something more suitable for comparison)

Like a pair of Wavac SH-833 power amplifiers, these seem to be more focused on ostentatious conspicuous consumption rather than high performance. I would expect to find better performance at very much lower price point.

Wavac SH-833 subjective review and measured performance (MF seemed to like these too):

https://www.stereophile.com/tubepoweramps/704wavac/index.html

Performance: I want amplifiers that provide adequately clean and load invariant gain, with output capability that is well suited to the application, and with balanced inputs and internal grounding schema compliant with AES48.

Bogolu Haranath's picture

That Wavac SH-833 has about 4 bits of resolution and costs $350,000 ....... This darTZeel-468 has about 11 bits resolution and costs $170,000, which is less than half the price of that Wavac amp ....... So, the darTZeel amp is a better deal :-) ..........

supamark's picture

I have one (a power supply cap finally failed about 2 years ago, haven't had it fixed/recapped yet). Just one would be needed (it's power output was VERY conservatively rated - think Pass XA25 conservative). It would certainly win in 1 area - power output, and probably win in bass control (almost certain - it's the thing the amp does best, and does it exceptionally well). might beat it on macro-dynamics due to greater output power. would otherwise likely get its clock cleaned.

jtshaw's picture

Mr. Fremer does a fine job of describing the sound of this amplifier. And I was thinking, why not just buy a pair of Wharfedale Dentons or Lintons, which to my ears are voiced to sound pretty much the same at comparatively miniscule money? I have a pair of Dentons attached to an AVM CS 2.2 all-in-one unit in a bedroom system, and the sound is so good I never feel deprived.

chuckles304's picture

Never could understand the name "darTZeel".....only now, upon learning the founder's name, do I see that it is simply a re-ordering of the name "Deletraz"....

Hmm

Bogolu Haranath's picture

They have all the 'Zeal' of Delétraz :-) ..........

drblank's picture

Then you should have a room like this.

https://www acousticfields com/state-of-the-art-acoustics/

ChrisS's picture

You don't recognize the color scheme?

Bogolu Haranath's picture

Yes ..... Great observation ........ Those are Iron Man colors :-) ........

Bogolu Haranath's picture

Crimson & Gold :-) ...........

ChrisS's picture

...Stark's "arc reactor" on the side.

ChrisS's picture

All you need is a "Tony Stark/MCU" signature...

tonykaz's picture

After all, Wilson $750,000 Loudspeakers have been featured in this Magazine.

What the hell are the Top 1% supposed to buy? , NAD you say ???

Of course, having pricy eye-candy on the Cover will sell Magazines at Book Stores. ( won't it ? ) Do these things look like something from Toys-R-us?

But still, can we expect any sort of relevance to Mainstream Stereophile Readership??

This Manufacturer murmurs about the quality of the Reviewer's Mains Voltage, I wonder why the Reviewer doesn't even have a PS Audio P20 Power Plant to insure adequate Mains Supply if trying to accurately evaluate the World's finest Amplification System. Or, why didn't the Manufacturer take steps to insure Review integrity ? ( Price no Object Reviews call for going all the way ).

Most of us will never meet anyone that "could" own this type of gear, insomuch as we are on the poor side of the Velvet Rope.

It's said to be a beautiful review. I might suggest that the Amps are as strikingly or purposely grotesque at those $750,000 Wilsons that Mr.JVS had his daringly embarassing picture taken from behind.

Maybe if I owned a Gold Toilet and a $5,000 Shower Curtain I could ....

Ok, lets make our Choice: these Amps or a Loaded Tesla S with about $60,000 Cash in the Glove Box for Impulsive Purchasing , can we have a Show of Hands?

Tony in Venice

ps. Dam good Journalism shows us how outrageous things can get.

JRT's picture

I have zero desire to own anything Tesla, and have more disdain for Tesla products than Bose products.

Unreliability:

https://www.consumerreports.org/car-reliability-owner-satisfaction/car-reliability-issues-models-lose-cr-recommendation-car-reliability-survey/

Invasion of privacy:

https://www.forbes.com/sites/kashmirhill/2013/02/12/teslas-elon-musk-reminds-media-his-cars-can-spy-on-them/

Monitoring and data logging is so excessive that some Teslas are now bricking due to flash memory chips are failing from too many write cycles.

https://www.vice.com/en_us/article/qvgxqp/worn-out-flash-memory-is-suddenly-bricking-tesla-cars

tonykaz's picture

Well, Okey, No Tesla for you

or me, I'll be riding 500 miles per month on a Cargo rigged Bicycle for the rest of my Life.

Tony in Venice

Bogolu Haranath's picture

FYI ....... Bose Model 700, Bluetooth, noise cancelling headphones ($400), were one of the 'Top-Picks' by the Sound & Vision magazine, recently :-) ........

Robin Landseadel's picture

"Of course, having pricy eye-candy on the Cover will sell Magazines at Book Stores. ( won't it ? )"

Not if people don't go to Bookstores in this age of Amazon/Kindle or aforementioned bookstores decided that said magazines weren't moving. About 15 years ago I worked at a "Borders", we had all the usual audio subjects on the Magazine racks, had to strip the covers to send back to the publishers and toss the 'zines into the dumpster most of the time. About a year ago, went to my local Barnes & Noble, they had only two "audio" titles on the racks. Used to find audio magazines in the magazine racks of supermarkets, those have been replaced with Gun magazines. I'll bet most folks reading Stereophile never encounter it in a Bookstore.

There's gonna be, say, a couple hundred people in this world who would even consider buying this ultra-pricy stuff. So I suspect it's really more about the magazine's writers getting their jollies at this point than anything else.

tonykaz's picture

Schiit just released Three Important NEW Products.

Audiophile Candy for Everyman.

1.) Made in USA ,

2.) Uncompromising Good product and performance,

3.) built by a group of loyal employees,

4.) sold at fair prices.

5.) Substantial Warrantee of 5 years.

6.) Company with a History of Integrity

7.) Schiit gear retains 80% Value for eBay re-selling.

Audiophile Readership have never been taken care of like today.

Tony in Venice

ps. I've owned a range of Schiit products but I'm not "rewarded" in any way by Mr.Stoddard or the Sr. Mike.

ps. Stereophile Staff were the ones that introduced me to Schiit back in 2011.

Ortofan's picture

... Schiit Sol turntables, yet?

tonykaz's picture

I'm not Turntable since I stopped Selling & Servicing every Brand of TurnTable Made, in 1985ish. Esoteric Audio had a compete Turntable Lab. with Tektronix Scope and critical Mechanical instrumentation for precision Set ups. We even did Cantiliver compliance measurements, suspension evaluations and Arm Mass matching. We were and are Scientists from General Motors Research Laboratory.

I embraced digital when Tyll & Steve G introduced me to Schiit & Sennheiser at RMAF2011.

I still own a considerable collection of Vinyl that I'll eBay at some point in the future.

My Psychiatrist and I have both had our Synapses rewired for the Great Digital Sound Quality. ( just like the Pro Audio people have done 100% )

Now, a presentable Vinyl System seems to electrify the Either in the Listening Room. That is it's magical power but I'm like Jabba the Hut, it doesn't work on me, I still see it's many flaws.

Tony in Venice

Bogolu Haranath's picture

Seems like Mr.Tony got tired of all the 'Stitching' and 'Non-Fill' on the vinyl records ....... (see AnalogPlanet) :-) ........

Faulty-thesaurus's picture

Michael claims that the mere existence of a (relatively) small number of wealthy people who purchase absurdly expensive audio equipment is a convincing reason to review this product. I’m not swayed by that argument.

supamark's picture

If you consider the market for this sort of thing as the "the 0.1%" in wealthy parts of the world (US, Canada, The EU, Australia, parts of Asia, etc) that's conservatively about 1 billion in population total. 0.1% of that (1 billion * 0.001) is about 1 million people. cut out 90% as not interested in audio/part of same household/whatever and that's still about 100,000 people who can easily afford this and might be in the market. Who do you think buys all that silly expenisve Nordost cable (who advertise quite widely in the audio press)? same folks (I know I ain't spending 10x my system price for speaker wire lol). I assume Nordost would not continue to widely advertise if it wasn't bringing results.

Add to that number those who like to read about crazy expensive gear and you've got a big chunk of this magazine's audience.

Plus, it's an interesting and unusual circuit design which carries its own appeal.

dial's picture

In the past there was Swiss Physics, FM Acoustic (I think it still exists) or Goldmund (originally french), all expensive. Here measurements, and looks don't please me. But I like the WBT cinch, beautiful color...

jeffhenning's picture

Ridiculous.

Not because of it's aesthetics... Personally, not a fan, but just fine if you are.

Ridiculous because this over-priced Lego-blocked POS can't outperform the best amps in the world that cost from $3K to $6K each.

darTZeel should be ashamed, but, hey, I guess there are consumers that truly don't care about ultimate sound quality at these prices. Wilson Audio proves that.

This amp is a bad joke.

To it's owners, "Even though your heart is breaking, laugh, clown, laugh!" (Think of the great Daffy Duck version)

Ortofan's picture

... (with the exception of KR, who uses Benchmark amps) seem to have an expressed preference for overpriced and under-performing amps?

(Wait for this month's "Listening" column from AD.)

ok's picture

At the time of the original NHB-458’s release I remember Deletraz stating that he was perfectly happy with the sound of his NHB-108 stereo amplifier though constantly pressed by some well-heeled, mostly Asian, customers to make for them something ..bigger. So let’s not blame the man for trying to keep his customers satisfied. I'm not even sure that hi-end audio customers nowadays are virtually outnumbered by the almost extinct but still noisy mid-fi ones –certainly not profitwise or else manufacturers would have never turned their backs to the latter in the first place. In the meantime ordinary people are mostly content with smart/phones or active solutions and for good reasons no doubt. By the way I have only heard the CTH-8550 integrated twice and save for some wooly bass it sounded truly magnificent.

dfh's picture

On the article's lead photo of the amp (angular view & front-face), the brass tag at lower center appears to end with "Michael Fremer" in script font (and has 4-lines engraving). In the front-face photo later in the article, the brass plate has the serial number (and 2-lines of engraving). Mr. Fremer's article states that externally the NHB-468 (review) and NHB-458 (Mr. Fremer's own amps) are very similar styling. Is the lead photo of Mr. Fremer's NHB-458, and the later photo actually the review NHB-468? Or as Mr. Fremer stated in the review, while he had no intention of purchasing the NHB-468's, was he seduced & gave-in to their enhanced performance! In any case an enjoyable read and thorough review (as always) by Mr. Fremer. Not only are my ears well trained, so are my eyes!

A_Stone's picture

Strange claim on the part of Dartzeel manufacturer:

Dartzeel claims:
A (Current)-Source with voltage source characteristics.
That is contradiction in terms and therefore incorrect.

A current-source with voltage-source output characteristics is a VOLTAGE SOURCE.

Good review and set of measurements.
However, simulated-speaker loading would have been appreciated.

Trevor_Bartram's picture

As someone who has just suffered a second sudden hearing loss event (was it the head cold or flu shot at fault?) I'm still amused when Mikey waxes lyrical about expensive gear, must be the masochist in me. However, he's really shot himself in the foot this time, who will buy his $140K amp now the $180K amp reigns supreme? Perhaps, like us mortals, it will be confined to the bedroom/kitchen/office system, ha, ha.

David Harper's picture

which would include me I always suspect that the economies of scale will dictate that this kind of gear will, in reality,turn out to be technically unreliable and not particularly better performing, much like the venerable Delorian or the aformentioned Tesla. I recently bought a new honda civic(a two-door sport with a 6 speed stick) which has turned out to be the best handling and driving car I ever drove for less than 20K brand new. And I've owned or driven far more expensive "high performance" cars. Economy of scale is an awesome and underappreciated thing.

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