LKV Veros PWR+ power amplifier Page 2

In jazz, the chief protagonist of the berimbau is, or was, Brazilian avant-garde composer Naná Vasconcelos, an especially inventive virtuoso who played with Gato Barbieri, Don Cherry, and the Pat Metheny Group. His 1979 album Saudades (16/44.1 FLAC ECM/ Qobuz) is a tsunami of percussive reverb and a good reviewing tool. Vasconcelos died in 2016.

Compared to Bel Canto
Switching from the Maggies to the Harbeth M30.2 monitors and using the Denafrips Terminator DAC, I began my comparisons of the LKV Veros PWR+ to the Bel Canto REF600M mono amplifiers—also class-D—using Saudades's first track, "O Berimbau." This piece seemed perfect for comparing how the LKV and Bel Canto mono amplifiers handle the berimbau's extreme transients and high-energy bursts of harmonic expansion.

The Veros PWR+ passed this test with an A+ by delivering a succinct, vibrant space wherein the berimbau "spoke" with musically effective acoustic power. Think strong, minutely detailed, and surprisingly wet. Almost tubelike. There was a radiance to the sound that I'd never experienced with class-D.

In comparison, with the Harbeths driven by the Bel Cantos, Vasconcelos's berimbau seemed flatter and drier. With the REF600Ms, it was playing in a smaller space, with less atmosphere.

The REF600Ms have long been my reference for properly implemented—fundamentally musical—class-D. But today, for the first time, in comparison to the Veros PWR+, their limitations were exposed. With the Bel Cantos powering the revealing M30.2s, this Vasconcelos recording sounded clean, quick, and detailed but also austere. In contrast, the LKV rendered berimbau notes with a more complex palette of overtones and showed infinite variation in string attack. With the LKV, soundstage depth was dramatically deep. With the LKV, the marginally annoying ECM compression seemed less noisy and more tolerable. What the LKV was doing seemed inexplicable.


Alternating wires
Every recording I played via the LKV Veros PWR+ was sounding richer and wetter (atmospherically) than class-D is supposed to. It occurred to me that perhaps the LKV's un–class-D atmospherics were, in some small way, being enhanced by the Cardas Clear Cygnus loudspeaker cables, which, in most systems I've heard them in, I would characterize as slightly warm, microscopically detailed, and exceptionally effective at preserving reverberant atmospheric data—all traits I was ascribing to the LKV.

As an experiment, I swapped in a pair of AudioQuest GO-4 speaker cables, which use solid-core conductors. In my experience, solid-core wire tends to make instruments and voices sound distinct and solidly outlined while sacrificing atmosphere. Generally, the GO-4's presentation is sharper, more toned, but less atmospheric than the Cardas's.

With the GO-4s, the LKV's sound became drier and more distinctly drawn. And because it was more distinctly drawn, the sound became more 3D. The soundstage was better mapped, especially with the Denafrips Terminator DAC set to oversampling.

With the GO-4s, the aforementioned berimbau became more tangible as a one-meter-high stick-and-wire sound-generator in front of a microphone. The AudioQuest cables better defined the room boundaries where the berimbau was recorded. The change to AudioQuest cables directed my attention to dynamic contrasts—jump-factor moments—and to the reverb specifically added to "locate" the berimbau in space. With the GO-4s, the LKV Veros PWR+ now sounded more normal class-D than it did with the Cardas Clear Cygnus.

The reverb tails appeared longer when I switched back to the Clear Cygnus. The room boundaries I noticed with the GO-4 became softer. The front edge of notes became less distinct. But the music sounded fuller and more engaging.

In for a penny, in for a pound: I tried Triode Wire Labs' American Series loudspeaker cables, which struck a neutral, extremely transparent balance between the Apollonian AudioQuest GO-4 and the Dionysian Cardas Clear Cygnus. The Cardas made the LKV amp sound liquid and atmospheric, but I was afraid it was adding something to the Veros PWR+'s sound. The AudioQuest provided definition and excitement but dried up the sound too much. The Triode Wire Labs cable seemed to add or subtract the least from what I believe to be the Veros PWR+'s natural character.

Driving the Falcon Acoustics LS3/5a
The LKV Veros PWR+ amplifier did a spectacular job of powering my current-hungry, 4 ohm Magnepan .7s and my resolving, 6 ohm Harbeth M30.2s. So naturally I wondered how it would do with my BFF, 15 ohm Falcon LS3/5a, which previously had not played well with class-D amplifiers.

After a long day playing King Tubby's dub (to ease my blues and loosen up the Falcons' voice coil assemblies), I played The Beauty That Still Remains and spied into the vast, intricate soundstage of the Norwegian Girls Choir and Anne Karin Sundal-Ask performing compositions based on the diary of Anne Frank (24/44.1 FLAC 2L/Qobuz). It kept me up late with its sympathy for, and faith in, humankind.

The Falcon LS3/5a's specialize in natural tone and high-definition soundstages. They have an uncanny facility for drawing focused pictures in the space around them. They take detail down to dust-particle size and separate individual voices in choirs. With the high-powered LKV amp driving the high-impedance Falcons, The Beauty That Still Remains seemed unusually 3D with a room-filling soundstage that reached the ceiling and penetrated the walls.


The LKV-Falcon pairing produced nuanced vocal dynamics with good transparency. The next day, though, I realized that the sound on some recordings was a little off: occasionally vague and low on boogie factor. Ultimately, the LKV Veros PWR+ and the Falcon LS3/5a loudspeakers were not a great match.

Compared to Rogue Audio ST-100
Next, I played The Beauty That Still Remains and Eriks Ešenvalds's Translations through the Rogue RP-7 preamp driving Rogue's $3495 push-pull, KT120-tubed Stereo 100 amplifier (footnote 2) powering my reference Harbeth M30.2 speakers. In only a few weeks, I had forgotten how open and fully described the ST-100's high frequencies sound. Now there was real space and genuine air. The midrange and bass became less dense than they were with the Veros PWR+. On every recording, the ST-100 delivered a lighter, brighter, sunnier—but less solid—presentation than the LKV.

Switching to sublime female vocals, Norwegian opera singer Kirsten Flagstad sounded serene and enchanted with the Rogue's tubes (Kirsten Flagstad Edition: The Decca Recitals, 16/44.1 FLAC Decca/Qobuz). Flagstad's singing was goose-bump magic with the Rogue amplifier but less magic with the LKV, which made her voice sound thicker and darker than the Rogue's tubes did. Each amplifier presents its own interpretation of transparency. The LKV colors its transparency with a kind of golden-honey quality. The Rogue's transparency was brighter and fresher and more natural—more transparent?

The ST-100 driving the Harbeth M30.2s is my primary reference setup. The 30.2s remind me of Quad 57s: electrostatic-quick and neutral of tone. Nevertheless, the LKV Veros PWR+ amplifier showed me how much weight and instrumental body the Rogue-Harbeth combo was losing through the bottom octaves. I wondered if I needed a "beefier" reference amp.

Sound quality and music enjoyment–wise, the LKV Research Veros PWR+ amplifier sits on a higher mountain than any other class-D amp I've encountered. It seems like Bill Hutchins made a slew of listening-inspired design decisions which, in concert, led to this extraordinarily natural-sounding power amp. I will be surprised if it measures super-low THD-wise, but, rest assured, I smiled contentedly every minute it was playing music in my room.

My thatched-roof stick-hut sencha-tea mind says $10,000 is a lot of money for three transformers and a few circuit boards in a not-fancy box. But is it?

With this LKV Research amplifier, you are getting something extra of unusually high value: Bill Hutchins. I have talked to him at length, and I can vouch for his character. He is humble and patient. He is a small, well-established audio manufacturer who builds phono stages, line amps, and big-system amplifiers in his shop with his own hands. I admire Mr. Hutchins because I once did what he is doing. Therefore, I know: $10,000 is underpriced for an amplifier built entirely in New Hampshire with the love and determination of one person. Long nights under fluorescent lights.

Today, most commercial loudspeakers feature reactive, low-impedance loads. Why? Because watts are cheap? Unfortunately, cheap watts often sound like crap watts. Fortunately, Bill's watts sound like limitless, sensual, tactile, luxury class-A watts. On the speakers I used, the Veros PWR+ put minnows, crappies, and my favorites, bass and catfish, into the once-empty class-D pond. Gleefully recommended.

Footnote 2: I used the 8 ohm taps and Ultralinear mode.
LKV Research
19 Randall Farm Rd.
North Conway, NH 03860
(603) 730-7400

Bogolu Haranath's picture

May be HR could also review the new PS Audio Stellar M1200 mono-blocks, hybrid tube/class-D amps, $6.000/pair :-) ........

dashendorf's picture

Class D suffers from power pumping. The cure is for the left and right channels TO SHARE the power supply. In other words, beautiful dual monoblocks are SUBOPTIMAL! Yes, heresy, but it is what it is.

Bogolu Haranath's picture

PS Audio another class-D mono-blocks, Stellar M700 are Stereophile Class-A rated ....... Bel Canto class-D mono-blocks, REF 600M and Black system are Stereophile Class-A rated :-) .......

a.wayne's picture

How is sharing the same supply gonna improve “ power pumping “ or is it pimping ..? :)

Ric Schultz's picture

How about a 3000 watt power supply for each channel.....choice of discrete input amp, Air core inductor on Purifi module....and tons of other tweaks.....including binding post bypass system. However, the air core coil is what is really something new. All class D amps till now used ferrite core inductors.....You would never use a ferrite core inductor in a xover of a speaker for the midrange and tweeter......this is common would wreck the sound. How come all class D amps have a ferrite core inductor on the output?.....for practical reasons....not sonic ones. Read more here:

I was reviewed July 1990 in Stereophile Mag. by Robert shunt attenuators were class A rated for 7 I bean around the block.

Bogolu Haranath's picture

The new NAD M33 uses Purifi modules ...... I don't know whether NAD uses 'ferrite core' inductors or not :-) ........

Several class-D, stereo and mono-block amps are in the Stereophile Class-A list :-) .......

Michael Fremer's picture

Five minutes ago

Bogolu Haranath's picture

Objectivists are Apollonian and subjectivists are Dionysian :-) .......

Lars Bo's picture

Maybe they're really both "subjectivists"? That's my understanding.

As an aesthetic pattern of "an accent" to sound and musicality, Apollonian and Dionysian "accents" both seem to clash with an objectivist-ideology of no "personality" in sound, verifiable by numbers, and, I gather, if so, musical honesty.

In any event, I applaud Herb for using these concepts (thanks, Herb).

Bogolu Haranath's picture

There is an interesting article, recently published in TAS about objectivism vs subjectivism (point/counterpoint) :-) ........

Ortofan's picture

... one of the amps from Nord Acoustics which also use the Purifi 1ET400A modules.
Their prices seems to be on the order of one-fourth of the price of this amp.

Is it Nextel binding posts, or should it be WBT nextgen binding posts?
Isn't Nextel that faux suede finish once used on various speakers?

Is the predominance of third harmonic distortion an artifact of the Purifi amp module itself or is it generated by the input/gain/driver stage that LKV adds?

Bogolu Haranath's picture

Third harmonic distortion almost similar to Krell K-300i? :-) ........

Bogolu Haranath's picture

One more ..... Similar to PS Audio Stellar M700? :-) ......

Bogolu Haranath's picture

One more again ...... Similar to Classe Delta monos? :-) .......

BillNH's picture

The distortion is, as JA observed, very low. The third order character is an intended characteristic of the LKV line level circuitry we have spent 8 years perfecting through seemingly endless listening and measuring sessions and innumerable circuit modifications. That circuitry is, I believe, largely responsible for the character of the sound Herb appears to have liked and found to be somewhat class A-like. The Purifi module does its job (principally current amplification) without adding or subtracting (almost) anything at all to or from the signal it is sent. It is simply the best, most accurate way I know of to get the signal from the line level circuitry to the speaker with the appropriately high level of power.

[[Bill Hutchins is chief designer at LKV Research--Editor]]

Thanks for adding that. I was about to do so.

Ortofan's picture

... LKV line level (input) circuitry, did you ever consider a design that might have its distortion characteristics dominated by the second harmonic, rather than the third?

If so, what made you choose the version with predominantly third harmonic distortion?
Or, if not, why not?

For that matter, and given that you're using the Purifi amp modules, why not develop a line/input stage with as little distortion as possible?
Would that approach result in an amplifier whose sound quality was somehow less "musically accurate"?

BillNH's picture

Yes, in developing the design for the phono/line level circuitry used in most of our designs, including the PWR+, we considered, tested and listened (almost to the point of distraction) to numerous circuits and topologies, including some that produce predominantly second order harmonic distortion. There were several goals we wanted to achieve, including very low noise, very low distortion (harmonic and slewing induced) throughout the whole audio frequency range (20-20KHz), natural sounding detail and dynamics. And, beyond everything else, we wanted reproduced sound that was as close to the sound of real voices and instruments as possible. Ultimately the circuit that gave us the best balance (at least to my ears) of these somewhat conflicting goals was a class A folded cascode, differential (balanced) amplification topology executed with hand-matched jfets, stiff current sources and no loop feedback (local or overall). As I you know, the 3rd order harmonic distortion is characteristic of the differential amplification. I hope this answers your question.

Bogolu Haranath's picture

JA1 compares the sound quality of JC1+ with Classe Delta monos, in his review of Classe Delta ...... JA1 says JC1+ has more 'tube like' sound quality ....... JC1+ has 2nd harmonic distortion and Delta monos have 3rd harmonic distortion :-) .......

Bogolu Haranath's picture

Seems like KR also likes the sound of 2nd harmonic distortion in the Parasound A21+ ....... Surprise, surprise, even the mighty Benchmark AHB2 has mild 3rd harmonic distortion :-) ........

dashendorf's picture

Ortofan's questions are very appropriate. The extra cost in the PWR+ versus other systems using Purifi or Hypex or ICE modules is due to using Class A, zero-feedback, matched components in the input circuits and using custom linear power supplies.

LKV's competitors are the 20 k$ & 30 k$ amplifiers, not the 2.5 to 3 k$ amps which use switch-mode power supplies and off-the-shelf input circuits.

Audiophiles generally seek the best quality and adjust for cost. The words "best value" are tricky. Best value? How about your phone connected to a pair of self-powered speakers? Claiming that other companies offer better value creates snickers from non-audiophiles (most of your friends and my friends): "3 k$ for an amp? What a moron. 10 k$? Yikes."

Bill Hutchins in an audiophile. He would claim: "The PWR+ offers BETTER quality at a LOWER cost than dual-mono blocks."

As for binding posts, Bill is an electronic designer primarily. He didn't hear the alleged differences. I do know that when a customer asks for WBT, for a small-charge he's installed them. Not a real issue.

Ortofan's picture

... various configurations, including mono-block, stereo with a single power supply and dual-mono stereo.

Also, they offer a choice of input stage op-amps, including a discrete class-A version.

dashendorf's picture

I know of many Class D amps. I know of $130 models that are good. LKV Research doesn't use opamps (many internal feedback loops), but does use differential Class A circuits and zero-feedback. Read the review. The sound is natural. LKV thinks of the PWR+ as Class A+D. The 1ET400 provides excellent output circuitry, LKV addresses other issues. Great sound results.

Bogolu Haranath's picture

As an industry veteran said it, 'the increasing importance of smaller differences' :-) ........

Ortofan's picture

... in the input/driver stage is somehow detrimental, do you hold that same position regarding the use of feedback in the Purifi power amp module?

dashendorf's picture

Ortofan, Again, a great question. The output stage requires a great deal of feedback - speakers are very physical and current demands are high. Getting the signal from a source to the output stage at the correct level while minimizing noise and distortion is the value of AZF Circuits, but the output stage is an entirely different animal.

Bogolu Haranath's picture

One could probably get the same results by using tubes in the input stage ...... See, Rogue Audio Sphinx V3 tube/class-D integrated amp measurements :-) ........

dashendorf's picture

Dear Bogolu,

Bill expects CLASS A tube amps to use Class D output. Obviously Rogue is. LKV expects the future of audiophile amps to Class A+D. LKV wasn't the first Class A+D, but Bill would believe he offers the best Class A input circuit. People can debate that. It's fun being an audiophile.

The second issue is adopting the Purifi 1ET400. It's quite simply the best Class D output. Not much debate.

Bogolu Haranath's picture

By using the Rogue RP-7 tube pre-amp, HR is getting some of that tube sound anyway :-) ........

Ortofan's picture

... whose circuitry does not employ any feedback?

dashendorf's picture

The Class A signal circuits in Bill Hutchins's designs employ zero-feedback which requires matched components. He believes this helps minimize a SOURCE of distortion. Many agree.

Ortofan's picture

... misunderstood.

What source(s) - such as a pre-amplifier , digital or analog disc player, tuner, recorder or streamer - are you connecting to this power amplifier whose circuitry does not already employ any feedback?

Or, are you possibly suggesting that the circuitry in this amplifier somehow reduces the distortion in signals from devices that are connected to its input?

In regard to the comment that "many agree", who are these "many"?
What quantity of these amplifiers has been built and sold?
Where would one go to audition this amplifier?

tonykaz's picture

Sound Engineers like Bob Katz, who is a real world perfectionist, favors Class D amplification.

Class D has had a successful future for some time already.

Personally, I love and admire Tubes from Russia despite them being fragile and having a rather short Half-life. Outstanding Solid State devices can seemingly last forever ( according to Nelson Pass ).

Tony in Venice

Ortofan's picture

... whatever happened to the Komuro 845 tube amplifiers?

Herb Reichert's picture

Komuro is an old friend
I gave those PP 845 monos back so he could sell them

He is still building triode amps at the leading edge of what is possible.


Ortofan's picture

... the Icon Audio MB845 MkII Mono, which is a push-pull 845 type tube power amp:

Alternatively, there is their Stereo 845 push-pull integrated amp:

Bogolu Haranath's picture

May be HR could also include the new Harbeth P3ESR XD speakers in the short list of products to review :-) .........

dashendorf's picture

tonykaz. Bill Hutchins has had a c-j tube power amp for decades. Loves it, but wanted to do better. He had to wait for a great Class D.

On the other hand, Class A amplification at low power with highly sensitive speakers remains wonderful. See:

tonykaz's picture

Low power with sensitive transducers is glorious.

I'm rather niche in my agreement with your statements.

I have felt the immenseness of powerful amplifications and tri-amping capable transducer systems, like being used in large theatres for iMax type installations.

One of my finest Music Systems fits in my shirt pocket and plays beautifully on any park-bench, Gulf Coast Beach, Air Travel seating. ( even during 20 mile bicycle rides )

Tony in Venice

Bogolu Haranath's picture

Please don't steal any mail-boxes, while during those bicycle rides ...... Just kidding ...... Just kidding :-) .....

a.wayne's picture

Hello ,

Maybe you can offer an explanation as to why Class D is so squarewave adverse , how is this instability overcome in music operation and as it should be audible is this possibly the class D sound most have an issue with ..?


tonykaz's picture

I can't offer any sort of design insights.

Personally, I'm at the point of embracing these efficient designs but not at the point of debating their limitations which seem rather minor.

There are a wide range of Analog lover's complaints.

Functionally, music reproduction advancements ( my opinion ) enable improved access to the dopamine that great music triggers the release of. We no longer need to sit square in front of a well tuned record playing set of planer loudspeakers and Class A tube gear.

How do Square-waves fit into our needs ?, I think I'm missing something from your question.

Philosophically considering, I suspect that electronic design and development is now in accelerated modes. I keep feeling that this next Decade will transition us to....??? . I recall being at RMAF2011 and having the feeling that the Audio Industry was mostly unrecognisable compared to the Audio Industry I participated in the 1980s with this last 10 years bringing amazing advancements i.e. iPhone11 ( for example ).

Fortunately, a person can still own and enjoy a beautiful traditional Tube based, VPI Koetsu Audio System and a state of the Art shirt-pocket traveling High End Audio System w/SD memory of zillions of music. All that wonderful Audio Research & Conrad-Johnson gear is still out there and widely available on eBay.

Wishing you well,

Tony in Venice

tonykaz's picture

Once again, this reviewer paints beautiful pictures.

I can see how a used book store will have a curious youth browsing (in the year 2075 ) this issue of Stereophile, stumbling across and reading this review taking him back to Mr.HR's Bunker Listening room and reliving this review experience.

Mr.HR creates amazingly wonderful art.

Thank You!

Tony in Venice

Kursun's picture

When you gaze at the pond and feel something is missing, it is distortion that is missing. The horrible crossover distortion that class AB amplifiers produce...

Class D is only second compared to Class A

JHL's picture

...a random commenter has graciously delivered the kernel of wisdom and insight our motley reviewer's ears and decades of acute experience had missed.

Why thank you random internet commenter. You have saved audio from hearing and indeed from ourselves.

michelesurdi's picture

stereophile is reviewing diy products now?

AaronGarrett's picture

The amp under review and the Bel Canto use different Class D modules. Isn't the difference in sound more likely due to the difference in the modules -- the newer Purifi module being touted by Putzey as much superior to the NCore -- than its particular, expensive implementation in this amp? But maybe that is what Herb is suggesting. Anyway thanks for the tip on the Nana Vasconcelos record! Great music! And the beautifully written review.

dashendorf's picture

AaronGarrett, you hit one of the main reasons:

  • Purifi provides better linearity above 15 kHz than competitors.
  • Linear Power Supply designed to prevent power pumping
  • Class A, Zero Feedback Differential Input Circuits
  • Matched components

There are many great designers. Bruno Putzeys may be the best. Bill Hutchins has leveraged Bruno's genius better than others.

thethanimal's picture

I thought a manufacturer was required to maintain a minimum number of distributors in order to be reviewed in Stereophile? Was this policy change in step with PS Audio’s change in business model? Regardless, it’s a change for the better in the age of internet direct sales. With this policy now changed I can’t think of a better product for Herb to review than the Decware Super Zen Triode SE84UFO, maybe to go along with those Cube Audio full range drivers he’s loved at audio shows.

Jim Austin's picture

Stereophile has long reviewed products from companies that sell direct, with appropriate return policy, as long as they can demonstrate the ability to provide satisfactory after-sales support.

Jim Austin, Editor

thethanimal's picture

My apologies; I have misunderstood the policy then. But I believe by all accounts Decware meets the criteria you have laid out for a review, and I believe such handmade, point to point wired, single ended tube amplifiers they offer would be right up Herb’s, or the late Art Dudley’s, ally. With much love given to Shindo over the years it’d be interesting to hear how an American competitor (or kindred spirit) would compare.

To the review at hand, an electrical engineer coworker insists to me that FET transistors behave in the same way as tubes; perhaps that’s part of the reason this amplifier (and some Pass-designed solid state amps) tickle Herb’s fancy the way they do. I can only offer up that comment for consideration by others without further detail, having gained only cursory knowledge during my own electronics courses while pursuing a degree in another engineering field.

Herb Reichert's picture

and I am preparing to write about Decware now. . . . stay tuned!


Bogolu Haranath's picture

If and when HR gets a pair of floor-standing multi-driver speakers, he could review the Rogue Audio Apollo Dark mono-block amps :-) ......

Bogolu Haranath's picture

May be HR could review the Rogue Audio DragoN, tube/class-D hybrid power amp ($4,000), and compare it with the LKV PWR+ :-) ........

JRT's picture

The listed specifications seem to have an error in the units of measure, "Input impedance: 200 ohms (single-ended), 400 ohms (balanced)."

I suspect that those values should be 0.2 megohms and 0.4 megohms, or equivalent impedance in other units of measure. No?

John Atkinson's picture
JRT wrote:
The listed specifications seem to have an error in the units of measure, "Input impedance: 200 ohms (single-ended), 400 ohms (balanced)."

You are right. I have corrected the input impedances on the Specifications page.

John Atkinson
Technical Editor, Stereophile

Glotz's picture

If I had the dosh, I'd check it out fer sure.

The Denafrips reviews were stellar as well. I want to check out their line more in depth. The Ares 2 looks like an excellent value and might prevent my purchase of a Benchmark DAC3B.

BillNH's picture

I should have said that I am the designer of the Veros PWR+.

Bogolu Haranath's picture

Mr.Bill Hutchins could consider a 5, 7, 9 and 11 multi-channel class-D amp :-) ......