As much as I admire Belgian amplifier designer Bruno Putzeys’s accomplishments, I have harbored some misgivings about class-D amplifier sound. I do not believe it represents the future of perfectionist audio. Despite the fact that today’s active loudspeakers depend entirely on class-D’s free horsepower, light weight, and low-temperature operation, I think it sounds vacant compared to class-A. Class-D’s primary engineering virtues are its extreme power-to-weight ratio and power-efficiency, as well as its high damping factor. Class-D’s chief audiophile virtue is its uncanny transparency, especially in the six lowest octaves, ie, below 1.3kHz. When I listen to good class-D (with a fat, stable linear power supply), I feel like I am gazing into a clear, glass-smooth pond. I can see all the way to the bottom. But (sigh) there are no fish in the pond.
As you already know, I am the Prince of Serendip. For this month I discovered, almost by accident, a power amplifier that puts live fish (and tadpoles and turtles) into a class-D amplifier pond.
The amp I’ve stumbled on is LKV Research’s $10,000 Veros PWR+ stereo amplifier. I first experienced it at Capital Audiofest 2019, where the sound in the LKV room—with the Sonner Audio Legato Unum loudspeakers—struck a remarkable balance between analytical and romantic. I knew something unusually good must be causing that. After a long audition, I told LKV Research’s chief-of-everything, Bill Hutchins, that I thought his Veros PWR+ amp sounded more class-A than class-D and asked, may I please review it?
Description
I went to the LKV Research website and clicked Products, then “Veros PWR+ Power Amplifier.” The first words I read were: “The Most Musically Accurate Power Amplifier Output Stage Available.” I stopped, read it again, then smirked at the expression “musically accurate.” I am pretty sure the author is trying to celebrate the fact that LKV Research founder Bill Hutchins uses Purifi Audio’s 1ET400A class-D power amplifier modules, designed by Bruno Putzeys. Further down the webpage, the author states that in the Veros PWR+, the 1ET400A modules are driven by a voltage amplifier stage consisting of differential pairs of matched JFETS operated in class-A with no feedback and current-source biasing.
The Veros PWR+ stereo power amplifier is specified to deliver 200Wpc into 8 ohms, 400Wpc into 4 ohms, and 220Wpc into 2 ohms, the maximum power assessed at 1% THD.
A little farther down, the author explains that the Veros PWR+ is equipped with a linear power supply energized by three toroidal power transformers. A 1kVA mains transformer, weighing over 12lb, provides abundant current to the class-D output stage. A second, smaller toroid powers a “floating” +15V DC source that feeds the driver circuitry in the Purifi module. A third toroid “feeds the class-A input/gain/driver stages.” All that heavy coiled wire is bolted inside a thick aluminum chassis. The Veros PWR+ weighs 50lb.
The chassis front is plain, with only the LKV logo and an illuminated power button. The rear is nondescript, with an IEC power socket, a screw-in fuse holder, a pair of WBT binding posts, a pair of single-ended RCA inputs, a pair of balanced XLR inputs, and a pair of minitoggles for switching between balanced and single-ended operation. The Veros PWR+ is hand-built by Bill Hutchins in North Conway, New Hampshire.
Setup
At first, I positioned the Veros PWR+ amplifier on the suspended hardwood floor in front of my equipment rack and connected it to my Magnepan .7 panel speakers with Cardas Clear Cygnus loudspeaker cable. I hooked it up to my Rogue Audio RP-7 preamp with Cardas Clear Cygnus interconnect. Straight out of the box, the LKV amp sounded fast, liquid, warm, and inviting, just as I remembered it from Capital Audiofest.
The next day, between music tracks, in the midst of pandemic-shutdown silence, I noticed a faint Lutron-dimmer– type buzz that seemed to be emanating from the LKV’s chassis. Checking first for hum, I put my ears to the speaker panels and heard only silence. When I examined the chassis with my stethoscope, I realized the sound was originating from behind the front panel, where the 1kVA transformer is bolted. I presumed the buzz was caused by the natural magnetostriction of the transformer coils being amplified by the amp’s chassis and the diaphragm of my 1920s wood floor.
Seeking a quick cure, I placed the Veros PWR+ on a Harmonic Resolution Systems M3X-1719-AMG GR LF isolation platform, whereupon the buzz was reduced to a point of serene inaudibility. With the LKV amp on the HRS platform, the sound of music recordings became noticeably purer, with sharper focus. A few days later, on a whim, I switched from the LKV-supplied generic power cord to an AudioQuest Tornado cord, which added bass punch, presence, sharper focus, and more silent silence.
Eriks Ešenvalds’s Translations (24/96 FLAC Naxos/Qobuz) is a high–dynamic-range recording with extended passages of extreme quiet. The added silence and clarity produced by these two (not-inexpensive) audiophile “accessories” increased my ability to observe, in a relaxed, focused manner, the nuanced inner workings of the Ethan Sperry–conducted Portland State Chamber Choir (footnote 1).
Listening
John Atkinson knew, as he was recording it, that this Eriks Ešenvalds Translations album would rev me up and engage me on a multitude of levels. He knew I’d recognize the nature poet in Eriks Ešenvalds’s compositions. And of course he knows how I relish the sound of choirs in sacred spaces and their vibrating masses of air. He knew how much I enjoyed his previous recording with Erick Lichte (producer) and Ethan Sperry conducting the Portland State Chamber Choir on Eriks Ešenvalds’s The Doors of Heaven (24/88.2 FLAC Naxos/Qobuz).
From the Qobuz liner notes: “The Oregon Poet Laureate Paulann Petersen, whose poetry is set on the first two tracks of Translations, stated: ‘Art is translation. Art translates mystery for us without destroying that mystery.‘” On this recording, “translates mystery without destroying that mystery” describes very well the serene, humanist spirit conductor Ethan Sperry elicited from his choir as well as the spatial acuity of Atkinson’s six-microphone recording. Everyone involved with the Translations project apparently demonstrated proper respect for choral sound, church chapel sound, and the intensity of Ešenvalds’s art. That respect makes this Naxos recording a gift to the ear and a sacred inspiration.
The LKV Research Veros PWR+, powering the Magnepan.7 quasi-ribbon panels, exposed all the delicate volumes of activated reverberant air that are held by this transcendent recording. Average class-D amps could never convey the full dreaminess of this type of choral poetic. Why not? Too much information would be missing in the upper octaves. But the class-D LKV amp played equally rich and atmosphere-soaked through the entire audio band. It did atmospheric dreamy like class-A does atmospheric dreamy. Surprising and impressive.
Bye-bye Portland, hello Brazil
The berimbau is a single-string percussion instrument that migrated from Africa to Brazil. It is fashioned from a meter-long stick, hollowed-out gourd, and a steel string, frequently one salvaged from the belting inside an automobile tire. Holding the gourd against his belly, the berimbau player strikes the metal string with a small stick called a baqueta while adjusting the wire’s pitch with a stone in his other hand. The berimbau’s sound is delicate—all buzz, snap, and resonance. Like a harmonica or jaw harp, the berimbau radiates full-spectrum harmonics, filling my listening room with buzzing, animated aural textures.
Footnote 1: All the observations below were made with the Veros PWR+ on the above-mentioned HRS platform and the generic, LKV-supplied power cord.
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COMPANY INFO
LKV Research
19 Randall Farm Rd.
North Conway, NH 03860
(603) 730-7400
lkvresearch.com
ARTICLE CONTENTS
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Specifications
Associated Equipment
Measurements
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