Steve Hoffman, mastering engineer

Steve Hoffman, Zeth B System

Pass Labs XP-17


Pass Labs XA160.8 – $27,300/pr.

The 160W, Class A XA160.8 monoblock is yet another inspiring and undisputable success from the mind of Nelson Pass—a man who for the past four decades (his first commercial product was released in 1975) has consistently risen to the challenge of besting himself.  At the frequency extremes, the XA160.8’s transient speed and pitch definition are superb, while its mids are simply extraordinary, possessing a purity, texture, and bloom that reminded reviewer GW of the best tube designs. Its paramount strengths are engaging resolution and transparency, with no vestige of glare or the faintest hint of edge.  A genuine triumph that earned GW’s highest recommendation. (259)

Pass Labs Xs 300 – $85,000/pr.

AHC has been using Pass amps as one of his references for years, and he had real doubts whether this new design from Pass could sound all that much better than what he was used to. Well the devil lies in the details, and the Xs 300 monoblocks provide those details in as neutral and accurate a manner as any amplifier he’s heard. Outstanding in all the usual areas for a reference-quality amplifier, but the deep bass and transition from the upper bass and midrange truly enhance the musical experience. So does a level of dynamic life and detail that has to be heard rather than described in words.  The Xs 300 brings out the very best in good recordings and will inevitably be limited by the quality of your speakers. Capable of driving even the most demanding speakers, it produces 300 watts into 8 ohms and 600 watts in to 4 ohms and has a maximum power output of 60 amps. (243)

Pass Labs INT-150 – $7150

Pass Labs’ first foray into the integrated amplifier arena has brought to market sixty pounds of 150Wpc, solid-state, aluminum-machined majesty. This powerhouse, which doubles its output into 4 ohms, offers neutrality tempered with pleasing warmth. It has an ease and fluidity that are not euphonically tube-like but emblematic of solid-state with a strong Class A bias. The INT-150 fleshes out vocalists and reveals the full physicality of power-singers, from deepest bass-baritone to lilting coloratura. Bass response is well-defined and highly controlled. Audiophiles who maintain LP and SACD collections will be especially rewarded by the INT-150’s wealth of micro-dynamics, fluidity, and a spatiality that really play to the strengths of these enriched formats. It’s a musical force of nature—a powerhouse design with a heart that should make anyone re-think the “separates” option. (184)

Pass Labs INT-250 – $12,000

A force to reckon with, the muscular INT-250 with 250Wpc (and 500Wpc into 4) embodies effortless dynamics, ultra-wide bandwidth, superb low-end control and grip, and effortless, unpretentious highs. Optimized for greater flexibility with grunt-worthy speaker loads of 86dB efficiency or less, its soothing and seductive sonics are an ideal companion for analog LP playback—this Pass integrated just makes you want to spin vinyl endlessly. Remarkable, too, is the amp’s lush midrange that pushes a loudspeaker to the very edges of its performance envelope. With musicality that is second to none, it operates at the outer limits of what is currently possible in today’s integrated-amplifier market. (263)

Pass Labs XP-30 – $16,500

Here you have two monaural line preamps sharing a single power-supply chassis—a stacked deck that crushes the competition when it comes to traditional solid-state virtues such as transient attack, bass control, and detail resolution. But the real magic is in bridging the great divide between the sound of tubes and transistors. Image focus and soundstage dimensionality are tube-like, as is the big tone and dynamic integrity. Microdynamic nuances and rhythmic drive are also convincingly reproduced. Orchestral crescendos expand from loud to very loud with absolutely no compression. Consistently faithful to the recording, the XP-30 refuses to dish out the sort of euphonic camouflage some solid-state amps do. A supremely musical line preamp that may well prove to be all things to music lovers and audiophiles alike. (223)

Pass Labs Xs – $45,000

An all out challenge to the state of the art and every other preamp available.
Pass Labs’ Wayne Colburn and Nelson Pass have truly outdone themselves in
producing this massive two-unit preamp. It does every right in every aspect
of sound quality and is so revealing of musical and soundstage detail that
you virtually have to listen to realize how good it actually is. Reviewer AHC
could not find any flaws even in comparison with other top preamps, and its
extraordinarily low noise floor and natural, detailed deep bass have few, if any
rivals. Male and female voice were excellent, and open and natural. Complex
organ passages were exceptionally clean, and so were complex orchestral
dynamics, opera, recordings of large jazz bands. Good form follows
functional styling, excellent features, and good ergonomics. AHC’s current
reference preamp. (243)

Pass Labs HPA-1 – $3500



The first headphone amp from Pass Labs, and hopefully not the last, the HPA-1 produced backgrounds that were as black as staring into black slate. Resolution was seemingly without limits, and low-level dynamics conveyed a playful sense of surprise each time they emerged from that dark space. In classic Pass fashion, the HPA-1 has been designed more like a power amp than a headphone amp, so there’s a lot of Class A bias from its hefty transformer, giving the amp ability to handle large voltage swings. It’s also a very capable line preamp that can output two sources—perfect for smaller spaces and systems. (273)

First Watt F7 – $3000

First Watt F7
First Watt F7

For over fifteen years First Watt has served as Nelson Pass’ creative playground, allowing him to explore unusual low-power designs with an emphasis on sound quality. The F7 is intended as an improved version of the popular F5, a 25Wpc stereo push-pull Class A amplifier. What makes the F7 so special is its inherent textural sweetness and warm tonality. There are many solid-state amps out there that manage to sound smooth and refined yet lack the organic character of live music. The F7, on the other hand, manages to sail through reproduction of violin tone with superb upper-register sheen and transient finesse—a rare feat for any solid-state amplifier. The F7 delivers far more incisive transients than tube amps, while its command of space is competitive with the sort of 3-D spatial presentation tube amps excel in. Simply put: one of the best low-power amps money can buy. (263)


Tone Audio issue “84” PASS Xa-200.8 TONE84_PassLabsXA200.8

Review from Steven Stone at Axpona High End Audio Show in Chicago in “the absolute sound”   July / August 2017


Innous’ new Zen MkII music server ($3499) was making gorgeous music in Room 504 coupled to the Aqua La Scala MKII Optologic D / A ($7000)… and Rethm Bhaava loudspeakers ($3900/pr.)… The Zen employs a linear power supply populated with ultra-low noise regulators and Nichicon MUSE capacitors, and has an anti-vibration treatment on its chassis.  It includes an independent floating optical drive and an internal hard drive platform.  The two gigs of dedicated internal memory allow music files to be loaded and played without having to constantly engage the internal hard drive.


Review from Julie Mullins at Axpona High End Audio Show in Chicago in “the absolute sound”   July / August 2017

Voxativ T-211 Integrated Amplifier

Based on the 211 output tube, the elegantly and thoughtfully designed, pure Class A T-211 single-ended integrated amplifier ($20k with remote) offers some remarkable features.  The latest brainchild from Voxativ‘s Holger Alder, this 12Wpc amp is handmade in Germany and its output transformers were custom-designed and made by Japanese artisan Masaaki Oshima, who views the transformer as a kind of musical instrument.  All the internal circuit paths are direct and there’s a 48-step attenuator volume control accessed by the remote control that –unexpectedly–makes adjustments by moving / rotating one of the two motorized dials on the front panel in a great mash-up of old school and new.  The second large dial is for input selection.  Through these dials dominate the front panel, their aesthetics and ergonomics are rather pleasing as a bold design statement.  They feel nice to operate, substantial yet easy to turn.  The chassis is milled from a 150-pound solid aluminum block with a smooth anodized surface–when the finish is this perfect, who needs paint?


“The INT-60’s dominant trait was to suck me in and glue me to my seat as it continued to reproduce music with so much low-key flavor, natural color, and more-ishness that I could never play just one record and go to bed early. ”      – Steriophile

“I strongly recommend that you check out this remarkable audio achievement.”                  -Positive Feedback

“if you want to hear beautiful music produced by an integrated amplifier that is built to last a life time and is one handsome-looking beast without constantly messing with your system, the Pass Labs INT-60 integrated amplifier is for you.”

Reviewers' ChoiceRethm’s polymath founder, CEO, and designer, Jacob George, is based in Cochin, in southwest India. He brings to loudspeaker design a nontraditional vision informed by his love of wide-frequency-band, high-efficiency, single-driver speakers, vacuum tubes, his trainings as an architect and engineer, and a musician’s ear. His passions for audio and speaker design were driven by his pursuit of a type of sound reproduction that existed in his imagination: fast, coherent, highly detailed, yet nonfatiguing. The products of that pursuit have been steadily refined, and have culminated in the latest Rethm loudspeaker, the Maarga ($9750 USD per pair).

Maarga in detail

In the competition for the attention of audiophiles in a seemingly endless sea of rectilinear box speakers, the modernist lines and shapely curves of the Rethm Maarga catch the eye. My wife and my mother, neither of whom is known for her fondness for high-end audio components, murmured appreciatively during the Maargas’ pre-Christmas unboxing ceremony — the first of several unusual listening experiences I had in the two months the speakers stayed with us.


Jacob George’s prototypes of his very first speaker were birthed in the early 2000s in Southern California, and were inspired by his being a music-loving artist and a relentless tinkerer. As he told me:

I was looking for a good, inexpensive speaker that could be powered by a low-power amp — not valves (tubes), at that stage. My first amp was a headphone amp-preamp built by Steve McCormack, and he agreed to build me a custom power supply that took the power up to something like 5 watts per channel. I started researching and read about “high efficiency” speakers. Somebody suggested Lowther drivers as a good DIY option and that is where it all began. Got my first pair of Lowthers, put [them] into an enclosure I made with tubes in my friend’s garage, and despite a lot of frequency issues, its immediacy, “realness” and ability to “connect” blew my mind. I was hooked into wide-banders. Being an architect gave me the ability and the confidence to “problem solve” and resolve the design issues. I have always done product design as well, but of course here the added functional element of dealing with acoustics became a fundamental design criterion. Design is a “process” . . . and can be applied to anything. It is about resolving the functional and the aesthetic into one harmonious and seamless whole.

Over the past decade, George dropped the Lowther 5” wide-bander in favor of a custom-designed, 6” driver made in-house. According to him, it’s much smoother in frequency response, and lacks the Lowthers’ infamous peaks while retaining their high efficiency, dynamics, transparency, and immediacy. In addition to the full-range driver, the Maarga has a powered bass section — two woofers housed internally in a sealed chamber, mounted in an isobaric configuration. George began with a custom-built, 75Wpc, class-AB amp and a passive filter, then moved to an active filter, then to a Chinese digital amp, and finally to a Hypex class-D amp rated at 400W. Late last year, he increased the size of the woofers “to get more punch and headroom in the bass. We went from a pair of 6”-diameter bass drivers to a 6” x 9” pair. This meant major changes as we had to redesign the enclosure, which ended up being 2” bigger in depth.”


I ended up being one of the first US listeners of the revised Maarga. It’s slim and deep, measuring 42”H x 7.5”W x 22”D. The bass unit forms a pedestal on which sits the enclosure housing the 6’ 8” labyrinthine horn. The pedestal is steadied by four easily adjustable outriggers. The metallic candy-flake enclosure has several finish options. Mine came in an attractive silver coat with beautiful side panels of sycamore.

The main, wide-band driver fires from the top of the enclosure. The downfiring woofers are hidden from sight in the base, with their volume and crossover controls (variable from 75Hz to 150Hz) on the rear of the base, along with the terminals. George believes that the shape of the cabinet is a critical design issue, and that a rounded cabinet sounds better than an angular one. Sensitivity is rated at 97dB/W/m at 1kHz, or “mean averaged from 200Hz to 2kHz.”

I am strictly a “form follows function” guy — even with my architecture. So the whole premise of the design of Rethms, from the very beginning, has been driven by how the sound waves emanating from the driver [are] best delivered to the listener. And this has two parts to it. One is the external propagation of the waves and how it interacts with the exterior of the enclosure, and the other is the internal behavior of the sound waves. Starting with the former, waves reflect off the first surface it encounters. And when these reflections “beam” at the listener from a uniform flat surface, it will compromise the pristineness of the original signals being produced by the driver because the listener is going to be hearing multiple waves milliseconds apart. So what I did was minimize any flat surfaces on the front of the speaker and that is how the “signature” curved shells of the Rethms [were] born. You will also note that the bezel around the driver is the only flat surface, and even that has holes to break up the waves that hit it. Now the second part is what it does for the back wave of the driver — which travels through the inside of the enclosure. Curved surfaces and volumes do not support standing waves. So the sound the listener gets at his seating position is extremely “clean.” The net effect is a complete lack of any “fuzz” and therefore great transparency and phenomenal soundstaging.

Given that I had several choices of amplifier to use with the Maargas, I asked George what he preferred. He responded, “I started with solid-state but, just like my first experience with wide-banders, I fell in love with valves (tubes) the very first time I heard one. I bought a very inexpensive EL34-based push-pull amp from Jolida, and the sound was an eye opener. SET’s were the culmination of that progression.”


I understand his preference for tube amplification. I, too, am a devotee, having fallen hard for a Shindo Laboratory Haut-Brion amplifier nine years ago, and three years later for a Shindo SET, the Cortese.

Test system

My listening was conducted with a Schiit Audio Yggdrasil DAC with the Analog 2 upgrade, an Innuos Zenith Mk.II Std. music server streaming Tidal and using Roon and an Apple iPad interface; a Garrard 301 turntable with Hana SL low-output moving-coil cartridge, Bob’s Devices Sky 30 phono step-up transformer, and Bob’s vintage-style phono cables; Shindo Laboratory’s Haut-Brion and Cortese power amplifiers and Monbrison preamplifier; Auditorium 23 and Skogrand Ravel interconnects and speaker cables; and power conditioning by a Shindo Mr. T. The only tweak I used was an Acoustic Revive RR-888 ultra-low-frequency pulse generator.

Behind the Rethm philosophy

I’m a practicing psychiatrist with more-than-passing interests in music and neuroscience, and my conversations with Jacob George revealed that his intuitions about listening to music align with my own, and are consistent with an explanation of brain activity found in Daniel Kahneman’s wonderful book Thinking, Fast and Slow. According to Kahneman, the brain processes information with two systems that operate simultaneously. System 1 works automatically, with little conscious effort or voluntary control. System 2 involves effort, concentration, and conscious choice. From this I extrapolate that if you find yourself thinking that a stereo sounds too “analytical,” chances are that it requires too much System 2 brain activity and not enough System 1: Cognitive strain mobilizes System 2. Stereos that put your mind at ease are likely stimulating more System 1 activity. System 2 involves your frontal lobe, the area of the brain devoted to attention and focus, while System 1 likely involves deeper limbic-system activity. Stereos that put your mind at ease are more likely to produce positive emotions, which is why most of us listen to music in the first place.

Gottfried Wilhelm Leibniz (1646-1716), a German mathematician who was one of the inventors of calculus, said that “Music is the pleasure the human mind experiences from counting without being aware that it is counting.” Contained in this observation is the idea that the pleasure of listening to a coherent, ordered series of sounds and harmonies is the pleasure the brain takes in engaging in an unconscious mathematical exercise. The precise reproduction of timing cues by highly resolving stereo systems reproducing performances of great music presents the brain with an exercise in parsing the mathematical relationships among rhythm, melody, and harmony, and that act of parsing gives the brain great pleasure because of this natural function of the mind. When the brain performs these pleasurable calculations effortlessly, they are by definition nonfatiguing and so tend to maximize pleasure, relaxation, and reward. Therefore, the best kind of speaker to come home to, to soothe our inner savage beasts, would be one that strikes a balance between resolution and the effort required to process that resolution. A single wideband driver per channel is an elegant way to achieve this psychoacoustic balance. A speaker with a single wide-band driver placed at the height of the listener’s ears is bound to be easier to listen to than a speaker with multiple drivers, each at a different height and each made of different materials, and requiring crossovers active in the midband, where most musical information occurs. George’s position is that the multiple wavefronts emitted by multi-driver speakers produce distorted harmonics and out-of-phase spatial information, as well as the potential for the smearing of low-level musical information. Phase accuracy theoretically leads to a more realistic, more informative, less fatiguing sound.

How did it sound?

Listening impressions

Juilliard-trained alto saxophonist Braxton Cook blurs the lines between musical styles while retaining elements of the traditional jazz he was educated in. His latest release, the fittingly titled Somewhere in Between (16-bit/44.1kHz, Fresh Selects/Tidal), is a startlingly fresh mashup of rock, jazz, R&B, funk, and electronica. With “You’re the One,” the Rethm Maarga strutted all its core strengths. A surging staccato synth line dropped me into a swirling vortex of sound. As Cook’s voice introduced the storyline — he’s found his perfect love — the Maarga masterfully choreographed and fleshed out the partners in the relationship: a fiery energetic electric lead guitar tamed by smooth, sultry sax counterpoint, until both dissolved into a soft percussion outro.

The Maarga’s uncanny ability to clarify the various musical lines and provide incredible detail for the sound of each instrument was also evident with “Hayati (My Life),” from Elwan, the latest from the Tuareg desert-warrior band Tinariwen (16/44.1 FLAC, Wedge SARL/Tidal). A single djembe pulled me in, then the fat bass groove, followed by an electric guitar as the singers begin a captivating call and response. It was remarkable to be provided with so much musical detail, and to be able to listen to it with no feeling of fatigue from information overload. Each instrument and voice was painted separately on the aural canvas, locked in to a specific area of the Rethms’ immense soundstage.


It was pure serendipity to stumble onto the music of virtuoso Shahnawaz Ahmed Khan. Acoustic guitar is an uncommon instrument for Hindustani classical music, but when I heard Khan’s bent notes, I thought it a match made in heaven. In “Placid Dreams,” from his Classical Guitar (16/44.1 FLAC, Worldwide/Tidal), Khan’s solo guitar lays out the outer borders of the melody in methodical fashion, marking the territory of the exotic scale, a swirl of ancillary fretboard squeaks providing just the right amounts of presence and detail. Halfway through, the tabla enters to provide rhythmic support to Khan’s soothing, soul-stirring guitar lines. The combination of the Maargas and my Shindo Cortese was especially luscious here, the amp’s single-ended-triode topology combining with the Rethms’ strengths to provide an ambrosia of natural harmonics. Acoustic instruments made of wood are a great test of any speaker’s realism because they create harmonics that are primarily even-ordered, and which tend to sound pleasing and soothing; odd-ordered harmonics tend to be more fatiguing.

The midband was in the Maargas’ wheelhouse, and women’s voices sounded special through them — seductive, mellifluous, never bland or cloying. In “Imagining My Man,” from Aldous Harding’s Party(16/44.1 FLAC, 4AD/Tidal), the voice of this goth-folk New Zealander is unique and mesmerizing. The Rethms and SET amp beautifully combined to communicate the longing and disappointment in Harding’s tone and phrasing, but what was really stunning was the depth of the soundstage: Her sultry voice seemed to hover in midair, and when the smoky exhalations of Enrico Gabrielli’s tenor sax takes the melody, it was as if he’d stepped into the spot just vacated by the singer as they performed in some intimate venue. Similarly captivating was “If the Storms Never Came,” from Joan Shelley’s eponymous 2017 release (16/44.1 FLAC, No Quarter/Tidal), her voice gently suspended over the gentle throb of bass guitar and delicately fingerpicked acoustic and electric guitars.

Male voices, too, were compelling, whether Sampha’s lilting falsetto in “Plastic 100°C,” from his Process (16/44.1 FLAC, Young Turks/Tidal), or Matt Berlinger’s smoky baritone telling the story of “Humiliation,” from the National’s Trouble Will Find Me (LP, 4AD CAD3315). And the Rethms were masterful with “God Shall Wipe All Tears Away,” from Ladilikan (16/44.1 FLAC, World Circuit/Tidal), a brilliant collaboration by the Kronos Quartet and Trio da Kali, the latter a remarkable Malian ensemble comprising singer Hawa Kassé-Mady Diabaté, balaphonist Fodé Lassana Diabaté, and bass ngoni player Mamdou Kouyaté. Heaps of harmonic information are contained in the fascinating interplay of the West African instruments, the European strings, and the majestic and spine-chilling singing, and the Maargas’ attention to these overtones will leave those of you with any religious leanings feeling as if you’ve just had an extraordinary spiritual experience. And if that last sentence leaves you feeling left out, don’t worry — you’ll feel the dopamine too; you’ll just interpret it differently.

Before hearing them, I was concerned that the Maargas would be hard-pressed to do justice to rock. I was wrong. The Rethms could indeed rock — not with the usual in-your-face, concussive, frontal assault, but in a more subterranean, earthquake kinda way when I turned them up loud. The flabbergasting thing was when I used them to listen to rock at low volumes. It’s hard to imagine that a speaker could deliver utterly compelling rock at a level of only 60dB, but that’s exactly what the Maargas did, and like no other speaker I’d heard.

With “Endless Ways,” from Anathema’s The Optimist (16/44.1 FLAC, Kscope/Tidal), the Maargas did a remarkable job of preserving the weight and scale at low volume. The wideband drivers conveyed all the dramatic tension of the gradual buildup, and boatloads of microdetail and ambient cues, particularly in the bottom end, let me enjoy “Endless Ways” in the living room with my family as they read. That’s no small achievement.

I asked Jacob George to comment on this feature: “Yes, low-level listening is one of the Rethm’s side benefits, thanks to its high efficiency. The added advantage the Rethms have is that the bass can be adjusted. I am sure you have heard of the Fletcher-Munson curves that plot the sensitivity of the ear between the variables of frequency and loudness. At lower listening levels, you will have to compensate by turning the bass up.”

Indeed, I’d turned the woofers’ volume pots almost all the way up, and set the bass crossover to 120Hz. The woofers added enough drive to provide surprisingly compelling low-volume sound. This was also true with “Hula,” from the Icelandic band Sólstafir’s Berdreyminn (16/44.1 FLAC, Season of Mist/Tidal). There’s a brooding intensity as the music crescendos into a full-on Icelandic avalanche, and layered piano, brass, strings, and operatic background voices transport me into a frigid and beautiful Arctic winter. Think icebergs crashing under the Northern Lights, and Sigur Rós on steroids. The Rethm Maargas seamlessly articulated the rich, deep bass guitar and drums; the thick, realistic guitar and piano tones in the midrange; and all the nice, tinkly high-frequency bits. Loads of drama will leave you playing air baton with this one.

Cueing up “When the Levee Breaks,” from Led Zeppelin’s IV (LP, LDL65778), I looked forward to hearing how the Maargas would handle John Bonham’s devastating bass-drum groove, a great test of bass reproduction. They didn’t shirk the task. Although with rock I preferred the Shindo Haut-Brion’s swagger and crunch through the Rethms, Shindo’s Cortese 10W SET was no slouch, due to the Maargas’ remarkable efficiency. What was even more magical was the reproduction of the special effects in this track. The sound of the Maargas plus Shindo Cortese or Haut-Brion was unusually engaging, revealing nuances in a long-familiar recording I hadn’t expected to hear anything new from.


Vanessa Fernandez’s cover of “When the Levee Breaks” is the best track on her album of that title, a collection of covers of Led Zeppelin songs (16/ 44.1 FLAC, Groove Note/Tidal). Yes, naysayers and purists, it’s not Led Zep, but it’s a pretty rendition, and the Maargas did a remarkable job of re-creating the depth and space surrounding and between her voice, Luis Conte’s lively percussion, and Tim Pierce’s slide and acoustic guitars. Listening to Stanley Clarke’s revolutionary electric-bass technique in the title track of his classic School Days (16/44.1 FLAC, Epic/Tidal) was particularly illuminating — not only were Clarke’s bass tones an incredible panorama of sound, but the Maargas were so revealing of his playing that I could visualize his virtuosity — slaps, strokes, tickles, pulls, hammers — as he coaxed unusual new sounds from his Alembic bass. The Rethms’ remarkable separation, lack of smearing, and imaging made each note easier to follow and “see.” And in Ray Gomez’s Strat-guitar lines I heard levels of sear, crunch, and bite that also served to correct my faulty presumptions about Rethms and rock.

I don’t often listen to large-scale orchestral music, but decided to play an LP given me by a client who’d found it at a Salvation Army store — an unopened copy of Shostakovich’s Symphony No.13, “Babi Yar,” recorded in 1970 and performed by Eugene Ormandy and the Philadelphia Orchestra (LP, RCA Living Stereo LSC-3162). This ancient recording of Russian symphonic music proved a fascinating test of the Maarga’s virtues. Tom Krause’s rich baritone commanded my attention despite the language barrier, convincing me of the tragedy and injustice of the slaughter, by German soldiers and Ukrainian collaborators, of 33,771 Ukrainian Jews in January 1941, near Kiev. When I closed my eyes, I heard a wealth of spatial cues that produced an enormous soundstage: a convincing simulacrum of the concert hall.

I then cued up soprano Kathleen Battle and guitarist Christopher Parkening’s delightful collection of duets, Pleasures of Their Company (LP, EMI Angel DS-37351), which has a more intimate sound. With the Brazilian composition “Boi-Bumba,” the Maargas revealed a wonderful liquidity and purity of timbre in Battle’s voice that sounded just right, and continuously interesting. Moreover, the Rethm’s coherence, lack of phase artifacts, and production of true harmonics combined to give me the illusion that I’d just flipped a switch on a digital surround-sound processor and had been transported from a large concert hall to a small salon. This was also evident when I listened to something evidently recorded in a venue of more medium size: a performance by the chamber ensemble Lautten Compagney of Philip Glass’s The Windcatcher, Pt.1, and Melody for Saxophone No.12, from his Recent Recordings (16/44.1 FLAC, Sony Classical/Tidal). What I heard was haunting, deeply evocative, and true to life: the Maargas reproduced each instrument’s tonal richness, as well as its distinct positioning on the soundstage.


The Rethm Maarga is a unique speaker with little competition. Yes, there are other speakers based on wideband drivers, but none that I know of that offer its combination of high efficiency, low-frequency performance, and value. The Maarga is an extraordinary combination of sound and vision. I found it well suited to music lovers such as I — those whose stereos are in the living room, not tucked away in a dedicated listening space. When they weren’t turned on, they were lovely pieces of furniture with high Wife Acceptance Factor. When they were turned on, they provided lively, enthralling sound that was immersive, real, and completely nonfatiguing. Given the Maarga’s fantastic sound quality at low volumes, it should also be well suited to the music lover who wants to listen late at night as the family sleeps. The Maarga might also be the ideal speaker for the music lover already smitten with low-powered amplification and/or tubes and who seeks a high-efficiency speaker at a moderate price (for the high end). The Maarga positively bloomed on that first watt, and needed no more than that to fill my living room with sublime sound.


That’s not to say that owners of high-powered solid-state amps couldn’t also fall in love with the Rethm Maarga, but such overkill would miss the point. If a big, beefy power amp is your thing, the Maarga’s allure will likely escape you. Think of a pair of mature, well-broken-in Maargas driven by a high-quality, cleverly designed, small-batch, low-watt amp as a long, complex, and magical marriage — a wonderful, many-layered mystery tour to your favorite musical places. I found that the Maarga’s strengths — microdetail, speed, soundstaging, coherence, layering, nuance, presence, depth — came alive with just the tiniest bit of power. With a pair of Maargas wisely driven by such an amp, prepare to exit the audio-upgrade merry-go-round.

Maarga is Sanskrit for path; the word is often used in the context of seeking the path to enlightenment. Is the Rethm Maarga your path to audio nirvana? I’ve found it to be mine. A must-listen for the music lover with worthy amplification.

. . . Tom Mathew

Associated Equipment

  • Integrated amplifiers — Luxman L-590AX, Spec RSA-F33EX
  • Power amplifiers — Shindo Laboratory Cortese and Haut-Brion
  • Preamplifiers — Bob’s Devices Sky 30 step-up transformer, Luxman EQ-500 phono preamplifier, Shindo Laboratory Monbrison preamplifier
  • Digital sources — Aurender X100L music server, Innuos Zenith Mk.II music server and Zen mini, Luxman DA-06 DAC, MHDT Havana DAC, Schiit Audio Yggdrasil DAC
  • Analog sources — Garrard 301 and 401 turntables on Chris Harban custom plinths
  • Cartridges — Hana SL, Miyajima Shilabe and Zero mono, van den Hul Crimson Stradivarius
  • Speakers — Horning Eufrodites Ellipse, Jamo R909, Vivid Audio Oval K1
  • Speaker cables — Auditorium 23, High Fidelity CT-1 Enhanced, Skogrand Ravel
  • Interconnects — Bob’s Devices Vintage phono, MG Planus 3, Sablon Panatela, Skogrand Ravel
  • Power conditioners — Shindo Mr. T, Silver Circle Audio Tchaik 6
  • Ancillaries — Symposium speaker stands, Kanso Audio Furniture, Acoustic Revive RR-888 low-frequency pulse generator

Rethm Maarga Loudspeakers
Price: $9750 USD per pair.
Warranty: Three years parts and labor.


Innuos Zenith MKII :  Can one call it stealth design when four facets mix it up on a component face plate? Perhaps that overstates but I must admit, this design trick did add dynamic flair to disguise an otherwise plain black box. Here’s looking at you, kid: the Zenith MkII music server/player, current flagship of Innuos, a brand still new to our domestic German market. Founded in the UK by two Portuguese in 2009, their HQ has since returned home to Faro/Portugal, an area which holiday makers to Agarve will know since it houses the region’s airport. Innuos offer two other models, the €850 Zenmini and the €1’800 Zen.

My pleasingly solid and well-finished loaner brooked zero confusion on matters of use. Aside from the standby switch, the faceted fascia only showed the slot of the internal Teac drive for CD rips. The lid carried the company emblem and things got busier only in the back: power IEC plus mains switch, 2 x USB-A (DAC plus back-up drive perhaps) and 2 x Ethernet (router, network player). Done.

Translated, no Toslink or coaxial S/PDIF output, no Bluetooth, no WiFi like B.M.C. Audio’s Mini Media offers. Querying Innuos’ product specialist Emanual Ey—after all, some listening rooms have no wired LAN—he explained that unlike a renderer, a music server deserved a wired connection to distribute whole-house data reliably. Also, WiFi injects ultrasonic noise into the machine to compromise its sonics as something Innuos would never accept – a dogmatic if familiar reply.

Hardware. During unpacking and setup, you begin to suspect that you’ve been shipped a small amplifier like the recently reviewed Creek Evolution, not a server. At 9kg, this is quite the buff deck. Bonnet popped, the culprit revealed itself as a 160VA toroidal power transformer. The Zenith runs off an old-school linear power supply that’s reportedly overspec’d by a factor of ten. It does not follow fashion with a potentially noise-emitting switcher.

Getting specific, there are three power supply paths with their own rectifier, filter capacitance (each >20’000µF) and voltage regulators. These feed the CPU; the remaining motherboard with optical drive; and the hard drive (1TB SSD option, 2TB/4TN upgrades for a surcharge). This triple separation safeguards particularly the USB and Ethernet outputs from distortion. Furthermore, there’s galvanic isolation and preceding the power transformer, a shielded AC line filter. All of it recalls classic hifi constructions, not computer tech.

Typically positioned in proximity to loudspeakers, a music server takes daily baths in strong vibrations. That equals microphony effects which our Portuguese battle with a maximally rigid enclosure and additional damping material in strategic areas. Here Emanuel Ey pointed out more advantages for SSD drives. They not only offer faster access times—tap on a song in the app and bingo—they don’t suffer moving parts which produce mechanical resonances. The less things vibrate, the better they sound. Then SSD work off lower voltages than classic HDD to allow smaller voltage regulators. Those turned out to be sonically superior. Listening to Ey for a bit and forgetting how we started, I soon suspected that he was on about point-to-point wired tube exotica. Alas, this is a computer with two 4GB RAM buffers, one of them as cache for SSD music data.

Software. Hardware pays only half the rent. To set up shop and do the business, the right software infrastructure is just as important. Ey talked about perfect integration with their hardware. Whilst platform-invariant software across endless computer models might offer similar functionality, code that’s been purpose-written for specific hardware and ultimate sonics pays back in kind. I was familiar with similar arguments from Carlos Candeias, engineer/owner of B.M.C. For their dance, the Innuos experts began coding their own BIOS firmware for the motherboard, continued with a proprietary Linux-based operating system and finally modified the Logitech Media server interface. In use meanwhile, the Innuos Zenith MkII didn’t shout ‘computer’ at all. That was down to its terrific GUI. I’ve never yet hooked up a music server faster. Plug in the LAN cable, power up, type ‘’ into the browser – and vroom.

Precisely because the interface was browser-based, I didn’t have to fire up a PC/Mac or install an app. Any smartphone or tablet can tag/import files, rip CDs and set up backups. So intuitive was this interface that any additional words on my part would only make it more complicated. Still, I want to highlight a few special features.

1/ Backup can be scheduled after, say 10 newly imported albums, rather more useful than timing it by date or days elapsed.
2/ Buying a 24/96 album from for example, the usual MO is to unzip the download, copy it over to the server via the home network, then refresh the latter’s index manually. With Innuos the zip file gets copied to a special folder. Click on ‘auto import’ and presto: unzipping, importing and tagging all unspool in one easy step.
3/ Should a CD rip suffer metadata issues or turn out to be a duplicate (something more common with me than you’d think), it gets quarantined automatically. This keeps the actual library clean and allows one to baby sit problematic imports separately. Regular imports are automatically sorted by quality (compressed, Redbook, high resolution) and issues with over-long names, special characters and such sorted.

During my time with it, playback wasn’t yet integrated into the browser. A forthcoming update will sort that. My loaner still relied on the mobile app exclusively. I tried SqueezePad and iPeng on my iPad. The penguin was decisively faster and friendlier. On look, feel and functionality, it actually stared down JRemote, JRiver’s app which I thought to be the best in the business. Until now. For androids there’s Orange Squeeze whilst Window cleaners have Squeeze Remote. My conclusion for the control interface is two thumbs way up. Competitors should take a lesson. I simply had one wish. I’d like to control the Zenith MkII from inside the Tidal, Qobuz and Spotify apps. These services are otherwise integrated already. iPeng does the biz but half the charm of streaming services is the impromptu discovery of new music. Here the native apps of those services simply work best.

Sonic impressions and comparisons. How does one approach a music server sonically? “It’s just a bloody digital transport” you say? For starters, Innuos’ flagship gets €2’700. Audiophile logic dictates that the DAC or streamer following belong to the same league since that’s, no trifle, where analog conversion will occur. Add an appropriate cable and one quickly hits the €6’000 jackpot for a complete digital source solution. Would that jive within a €9’000 system? I’d say not. Personally I prefer to allocate 2/3rd of my budget to the amp/speaker combo. That should be maximally transparent and lucid or otherwise you won’t hear at the back end what happens upfront. And something else: if you’re the type audiophile who prioritizes tonality above all else to enjoy good soundstaging, resolution and timing as nice to have but not essential… stick to a laptop transport. Invest your discretionary hifi funds into music, not hardware you won’t need. At least for myself, I’ve never yet observed serious tonal alterations by swapping digital transports. On that count, they all sound pretty much indistinguishable to me. Playing it perfectly linear, the big Innuos did nothing to change that assessment.

My first contrary discovery happened by accident. Out of pure habit, I didn’t wire the Innuos directly into my Luxman DA-06 converter but via iFi’s iPurifier2 which docked in its USB port. This thumb-drive gizmo filters and “rebalances” (whatever that means) the USB signal before it hustles over to the DAC. It sounded pretty good but A/Bs are of course best done direct and without intermediaries. Out came the iFi for a reboot. Cue raised eyebrows. Defying convention, ‘direct’ sounded better. Usually it’s the other way. iFi’s little helper routinely contributes greater calm, focus and grip; precisely why it remains plugged into my Luxman. The Innuos on its own had so much body and plasticity that not only couldn’t the li’l iFi improve upon it, it put a minor damper and veil on/over micro resolution. For once, ‘without’ sounded more clear, direct and transparent. Old dog, new trick. I continued in ‘pure’ mode to face off the Portuguese against three other transporters.

The first any deck like the Zenith must wipe the floor with is your garden-variety Computer Emporium laptop. The Zenith MkII aced that test with flying colours. My JRiver-17 fitted Notebook didn’t stand a chance. Instruments got paunchier and flatter, precision diminished, stage visibility fogged up and the depth dimension congealed. I had the impression that the Innuos gripped each tone tautly to banish all seam fuzz and diffusive auras. It also trumped with better timing that didn’t eat into sustains and delineated the bass far better. Even the higher registers on vocals or piano improved. Nothing was indistinct spatially or in the time domain. Soundstaging focused down and beat fidelity went up. Granted, my heroically indestructible laptop sold for less than a quarter but purely on sound, it just couldn’t keep up. Sniff.

The second challenger was Auralic’s Aries streamer. This purist network player without DAC or hard drive must be bundled with a NAS to compete but that combo should still be ~25% less than the Portuguese. Now the blatant gap against the laptop was no more. The Aries is a very good machine. Still, judged by the book, the Innuos had the edge on a few points. Its micro resolution was a bit higher, sounds had more body, the depth perspective gained a tick, bass got grippier and rhythmically more assured. True, I could hear some argue that “though the Aries painted instruments and voices with a bit less grip, it did them bigger and closer up which involved me more”. This I follow in theory but not personally. Rephrased, the sonic offset between Auralic and Innuos was subtle to transcend the purely objective and play to different listener tastes.

Very much the same happened against the Audiodata MusikServer MSII. On price and concept a virtual stand-in, the sonic differences were a replay of the above. Some will favour the half-step forward perspective of the German and its slightly wider if shallower staging. Others will champion the resolution gains, tauter timing and greater focus of the Innuos. This I would call like I did the Auralic. Whilst subjective preferences differ, judged by the book I’d call the Innuos first.

Conclusion. With their flagship Zenith MkII, our newer firm Innuos has a music server/player that’s very solidly made, attractively styled, super fast due to its SSD and a poster child for user friendliness and intuitive use. Particularly the browser interface makes chores like tags, rips, imports and backup scheduling easy as pie. This should be the gold standard. The playback apps I sampled followed suit, including integration with Spotify, Tidal and Qobuz. The integral UPnP server supports multi-room and streaming configurations from Naim, Linn, Moon Mind, B&O, Denon Heos & Co and one button press can even sync the Innuos library with Sonos. Many audiophiles will predominantly rely on player mode as the direct USB connection with a DAC. That interface was executed very well. And… an additional coax and/or Toslink would be lovely. From a sonic perspective, as part of a quality system that’s transparent and highly resolved, a digital transport to stream audio files from makes a difference. Here the Zenith MkII did a terrificjob as a career audiophile of purist leanings: tonally neutral, ultra resolved, rhythmically in the pocket and spatially dimensional. At its price, I’m not aware of competitors which objectively would be “more correct” – merely those that do it different if no better. Chapeau time! Where total packaging is concerned (fit’n’finish, ease of use, sheer access speed and sound), the Innuos ties it up with a bow. Trials and auditions are in order. Given 30-day return privileges, there’s zero involved risk.

• Category: Music server/player
• Dimensions & weight: 70 x 420 x 320mm HxWxD, 9kg
• Trim: black
• i/o: 1 x USB 2.0 (DAC), 1 x USB 3.0 (backup), 2 x RJ45/Ethernet (LAN and streamer), 1 x VGA (service only)
• Format support: PCM to 32bit/352.8kHz, quad DSD, WAV, AIFF, FLAC, ALAC, AAC, MP3
• Power consumption: circa 10 watt at idle
• Other: dealer network under development as of 3/2017, direct sales via maker or Amazon possible
• Warranty: 2 years

– Translated from April 2017 issue of high-end hifi magazine of Germany as seen in 6moons


Step up! Aqua Hifi’s La Scala MKII Optologic DAC

Back in March 2014, Aqua Hifi’s visually unassuming La Scala MKII D/A converter not only took out a DAR-KO Award but landed pole position on the Darko DAC Index, beating out contenders from AURALiC, Resonessence Labsand PS Audio.

Without trading in on vibrant acoustic mass or tonal colour intensity, albums like Fila Brazillia’s Maim That Tune, decoded by the La Scala MKII, maintained their deeply-rooted, sometimes micro-dynamic, rhythmic urgency and inside-out pressurisation without weight loss to basslines or a cooling of the album’s Ready-Brek glow. In a word, bellissimo!

In (under-)scoring this success Aqua R&D man Cristian Anelli bucked modern DAC trends at almost every turn: 1) a ladder R2R decoder with 4 x Burr Brown PCM1704-K silicon laid out in fully-balanced, dual mono configuration with; 2) On-chip digital filters bypassed in favour of the Milan company’s own logic-gated, non-upsampling Direct From Decoder (‘DFD’) circuitry. 3) fully discrete I/V conversion; 4) a hybrid output stage with 2 x ECC81(12AT7), each with two MOSFETs apiece. 5) Optocouplers separating analogue and digital boards.

At €4890, the then top-flight Aqua offered more attainable high-end performance. For pragmatists, a considerably more nourishing take on Redbook material made the hit to broader file format compatibility – no DSD, no PCM above 192kHz – a cinch to absorb.

September 2015. Anelli struck DAR gold again, this time at a lower price point with the La Voce S2: a pair of Burr Brown PCM1704-K R2R ladder chips running in dual mono. The entry-level unit lacked the “true differential” chip config of its bigger bro and sported a less sophisticated DFD circuit. The results once again spoke for themselves; a DAC seemingly built to hold back some of the brutal truths of contemporary (read: non-audiophile) music’s highly variable recording and mastering quality. An ideal fit for Future of the Left, The Hold Steady, The House of Love’s (proper) debut, Guided By Voices and The Mountain Goats.

Also withheld from the La Voce S2, a glass n’ gas / MOSFET output stage, thus highlighting this Aqua-man’s pragmatism – Anelli couldn’t be accused of a singular approach to DAC design.

This pair of over-achievers have since remained references at DAR, deployed according to mood and (especially) music preference. For deep insight into Sandwell District’s intergalactic journeys or Thomas Dolby’s melancholic The Sole Inhabitant or Eno/Hyde’s High Life, the La Scala MKII gets the hook-up. For Suede or Joy Division, the La Voce S2 gets the nod.

January 2016. A tube upgrade to NOS Telefunkens, as suggested by Aqua’s US handler Well Pleased AV and since adopted by the manufacturer, took the La Scala MKII’s audible performance up a notch; between the La Scala MKII and heel-tapping rivals, more distance was driven.
May 2016. The first kink in this (thus far) PCM1704-K-centric narrative. At Munich’s High-End show, Aqua Hifi spilled with news of – and gave a first public outing to – a new flagship D/A converter, the Formula (€12,500).

The big news was that the TI/Burr Brown silicon had made way for in-house developed ladder R2R network boards, once again combined with the optocouplers previously seen in the La Scala MKII (i.e. ‘Optologic’). In one hit, Aqua would sidestep dwindling supplies (and higher pricing) of the long discontinued PCM1704-K chip and potentially better their sound quality by (also) minimising electrical noise interference.

The Formula’s formula: two R2R modules per channel, one for each half of the sine wave, with all incoming digital data marshalled by a proprietary algorithm located on an FPGA chip.

Also new, a revised USB board – XMOS input, i2S output – that would extend PCM compatibility all the way out to 384kHz PCM. That’s twice the ceiling height imposed by the outgoing Burr Brown.

Once again, Aqua’s DFD would stand in for the usual digital filter. According to Aqua’s softly-spoken and camera shy marketing man Stefano Jelo, DFD is one way in which the Italian company maintains a certain degree of house sound.

The Formula’s audible aim? (An even more) vivid reproduction of music.

More info can be extracted from this video:

Like the La Scala MKII before it, modular upgradability would be baked into the design.

Some two years prior to the Formula’s Munich launch, Cristian Anelli wrote of the La Scala MKII: “What is important for a modern DAC is to avoid obsolescence: Aqua’s philosophy allows all previous customers to replace the conversion modules (and new PCB releases) as easy as possible.”

The upshot? The Optologic R2R and Xilink Spartan FPGA housekeeping modules would soon be adapted to the La Scala MKII.

October 2016’s RMAF saw Aqua Hifi make good on this Munich-made promise. Mark Sossa of Well Pleased AV had the Stateside scoop (as well as some DJ Shadow):

Not a full point upgrade to MKIII status but a MKII Optologic revision. Price? €6600. Existing owners could dial up a factory-fitted upgrade for €1000.

January 2017. From the outside, the Optologic and Burr Brown models look identical.

On the front panel of each unit, we see the same power switch, the same source selector, the same digital phase inverting toggle and the same slit window for tube heat dissipation.

Out back, the same inputs (AQ Link i2s, USB, coaxial, BNC, AES/EBU) and the same outputs (single ended RCA and XLR balanced).

To observe real differences, lids would need to be popped. Sitting the open Optologic box next to its predecessor, we see how the Formula’s four separate ladder DAC boards, populated with “low noise precision resistors”, have been distilled into a single slab that sits top right as we observe the Optologic DAC from front to back.

Below that, some minor changes to the analogue board: twice the number of (blue boxed) capacitors; no more trim pots; and the LEDs are now green where once they were red. The tubes are the aformentioned Telefunkens.

Transformers on the new fella’s XLR outputs means a little more daylight sits between balanced and unbalanced listening. At least, that’s the way I heard it with an all-balanced chain from PS Audio BHK 300 monos back to PS Audio BHK pre-amplifier with ELAC Uni-Fi F5 loudspeakers working the business end but confirmed by the PS Audio’s pre’s headphone output driving Sennheiser HD800S: the Optologic’s balanced output seasons its sauce with a little more vitality. The upshot is a little more audible flexibility for the end user should s/he demand it.

Formula trickle-down also meant a revised USB board (top left) with broader file format compatibility; the Optologic La Scala MKII can decode PCM up to 384kHz as well as DSD64 and DSD128 – another reason why Aqua’s ditching of PCM1704-K DAC chips makes marketplace sense.

To its USB socket I connected the newcomer to the Sonore’s microRendu network streamer with AudioQuest Carbon wire and pulled up Robyn Hitchcock’s A Star For Bram via Roon. Then Robag Whrume’s Wuppdeckmischmampflow. Then David Bowie’s Aladdin Sane.

Much has changed in the digital audio world since we first met the original La Scala MKII. Chief among the bigger developments is MQA and its recent landing on Tidal.

Streaming the MQA-d version of Aladdin Sane via Meridian’s Explorer2 (US$299) reminds us that the DAC matters more than file encoding/encapsulation methods. Moving from either Aqua (with ordinary 16bit/44.1kHz streams) to the Meridian with MQA, we lose soundstage height, tonal colours show up as more diluted and layers congeal.

Then there’s the increasing popularity of FPGA-fuelled D/A conversion, most notably from the UK’s Chord Electronics and the USA’s PS Audio. The latter’s DirectStream DAC recently returned to the DARhaus for an extended European vacation. At US$5995, it plays in the same field as the original La Scala MKII and Optologic newbie.

The Optologic La Scala MKII doesn’t play through as much humid warmth as its Colorado born rival. It sounds cleaner and more direct with considerably less obvious transient edge rounding. On large/r scale dynamic drama, particularly with electronic music, I’d rate these two DACs as equals.

Where the Optologic’s presentation deviates further from Ted Smith’s FPGA-er is in two key areas: 1) the Aqua shines more light between the notes – connective tissue isn’t as thick as it is with the DirectStream; 2) there’s a greater sense of speed in Italian hands – we feel as though rhythms drive us faster through the music when in fact we’re just closer the road where surface textures are more palpable.

Which DAC is better? I prefer the Aqua but some of you may not. The DirectStream’s warmer tonal balance makes it better suited for those moving from vinyl to digital world for the first time. The PS Audio also offers gives us more functional opulence than the Aqua: a colour touchscreen, a remote wand, a TOSLINK input (not to be undervalued) and the possibility for in-built Roon Ready network streaming.

However, the Aqua’s talents in clearing space for the subtlest micro dynamic shifts and rhythmic rectitude make for a more invigorating listening experience. Think: sparkling mineral water vs. a milkshake.

Compared to the original La Scala MKII, the Optologic edit’s first fundamental advantage is a deeper inking of tonal colour. One visual touchpoint might be an illustrator’s shift from pencil to crayon.

Secondly, intra-note information enjoys more time in the spotlight at the hands of the in-house R2R-chipped variant. On Mike Garson’s piano playing, we note more abundant ambient decay. The Optologic Aqua is the DAC for those who get off on micro detail extraction and copious amounts of recording space information – ingredients that sum to an altogether more immersive listening experience.

Thirdly – and perhaps most importantly – the updated unit underscores and amps up the original’s inside-out pressurisation. Music positively bursts into life. For the sinister jazz and macabre vocals that dominate Angelo Badalamenti’s score for Twin Peaks: Fire Walk With Me, we hear more deeply etched player outlines delivered with nary a hint of rigidity. The all-important sense of effortless is maintained, especially with microRendu in play.

In other words, the most satisfying DAC heard by yours truly to date just got significantly better. Modularity coupled to a manufacturer upgrade programme brings owners of existing La Scala MKII in from the cold (should they wish to).

In its Optologic incarnation, the La Scala MKII cements further its position at the very top of the DAR-KO DAC Index and DAR-KO Award assignation becomes as easy as it has ever been. In a word, primo!

Further information: Aqua Hifi


Reviewer: Srajan Ebaen
Financial interests: click here
Sources: Retina 5K 27″ iMac (4GHz quad-core with Turbo boost, 32GB RAM, 3TB FusionDrive, OSX Yosemite. iTunes 12.2), PureMusic 3.02, Qobuz Hifi, Tidal Hifi, Fore Audio DAISy1, COS Engineering D1, Aqua Hifi La Scala MkII, Metrum Hex, AURALiC Vega
Preamplifier: Nagra Jazz, Esoteric C-03, Vinnie Rossi LIO (DHT module)
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1, F5, F6, F7; S.A.Lab Blackbird SE; Crayon Audio CFA-1.2; Goldmund Job 225; Gato Audio DIA-250; Aura Note Premier; Wyred4Sound mINT; AURALiC Merak [on loan]
Loudspeakers: Albedo Audio Aptica; EnigmAcoustics Mythology 1; Sounddeco Sigma 2; soundkaos Wave 40; Boenicke Audio W5se; Zu Audio Druid V & Submission; German Physiks HRS-120; Eversound Essence, Rethm Bhaava [on loan]
Cables: Complete loom of Zu Event; KingRex uArt, Zu and LightHarmonic LightSpeed double-header USB cables; Tombo Trøn S/PDIF; van den Hul AES/EBU; AudioQuest Diamond glass-fibre Toslink; Arkana Research XLR/RCA and speaker cables [on loan]; Sablon Audio Petit Corona power cords [on loan], Black Cat Cable redlevel Lupo
Power delivery: Vibex Granada/Alhambra on all components, 5m cords to amp/s + sub
Equipment rack: Artesania Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands [on loan]
Sundry accessories: Acoustic System resonators
Room: 5.5 x 15 metre rectangular space with double-high vaulted ceiling and stone-over-concrete flooring
Review component retail: €6’600 [€1’000 factory retrofit]

The headline reads LaScala MkII. The product photo says Formula. What’s up? Today’s review is a follow-up on the Formula’s feature writeup. Once his flagship DAC bowed, Italian designer Cristian Anelli instantly busied himself to apply his newly minted discretech to the previous range topper. The link gives the full back story. For today’s purposes, we’ll only extract that the optologic makeover of the LaScala MkII replaces its former BurrBrown 1704K multi-bit chips with a discrete R2R ladder board of slightly lower specs than the twice-priced Formula whilst retaining the original’s Mosfet-coupled tube output stage. So what’s up is a good hifi-class grade: an upgrade that may be retrofitted to original MkII. That cashes in on Aqua’s concept of modularity which leaves no man or woman behind. Because this makeover goes deeper than a USB board swap, a return to the factory is required.

Earlier in the year, Sino reader Yu Bai wrote that “recently a famous Chinese audio reviewer compared the Aqua La Scala MkII to the Chord Dave and Prism 8XR converters. He clearly chose the Aqua as the best.” Sydney-turned-Berlin contributor to these pages John Darko lists the same machine on the top spot of his personal DAC index. Yours truly has used it as one of his reference decks ever since its review. German colleagues at gave it top marks as well. In short, with this machine Aqua gained quite universal accolades for sonics, build and relative value.

Now LaScala v2016 turns its back on dwindling supplies of NOS silicon and joins the ranks of discrete ladderists like Aries Cerat, LessLoss, MSB, Rockna, S.A.Lab, TotalDAC, Wagner Audio & Bros. This contingent plays counterpoint to the cadre which converts all PCM to DSD like AK Design, Meitner, Nagra, PS Audio & Co. who clone 1-bit converters from custom-written FPGA code. The far bigger middle ground between these two camps is taken up by the Sigma Delta brigade which, these days, seems to fancy ESS Labs Sabre chips over most others though Asahi Kasei, Crystal, TI and Wolfson remain popular. Finally there is a small group with members like Metrum Acoustics and Schiit who pursue the R2R multi-bit route with on-chip solutions from either the industrial sector or self-rolled; or who do everything by FPGA like Chord.

In my Formula review, I compared the original LaScala MkII to the Formula. Today focuses first on comparing old and new LaScala MkII. This assignment is thus particularly for owners of the original who may wonder what a €1’000 retrofit buys. For starters, let’s look at what changed materially; rather more than a single new PCB module. To avoid charging for face plate swaps or sticking a tacky MkIII badge on the back, Aqua wisely opted against a name change. The MkII remains a MkII. The new opto logic hides beneath the bonnet like grey matter inside a skull: out of sight but responsible for the IQ.

Some quick eye toggling shows four different circuit boards including the output module which remains recognizable but has undergone permutations to adapt to the upstream alterations. Even the USB module is upgraded to now support 384kHz sample rates up from the 192kHz limit of the illogical MkII. With a rebuild, one assumes that Aqua have to scrap the old boards since new production no longer uses them. Whilst a reviewer can’t do da bom—the bill of materials—to break down assemblies into fixed figures, given the extensive overhaul, €1’000 for a retrofit seems very fair against the original’s sell price of €4’890 (ex VAT).

The analog board shows different relays, twice the number of capacitors, no more trim pots and changes to the LED current source parts. Except for a change from orange to green LED, the power supply appears unchanged. “Unlike the older version, the new La Scala MKII Optologic, like the Formula, has transformer-based XLR outputs.”

How do the MkII’s optological bits differ from the Formula? Here is a look at the latter’s R2R module showing three of its four ladder modules…

… versus the simpler single board of the MkII Optological. What remains true regardless is exploded parts density. Where competitors get away with a DAC chip smaller than a postage stamp, these discrete R2R ladders require a lot more.

Hardware. To suss out potentially difficult-to-hear differences, I opted for a deliberately minimalist amp/speaker combo: single-stage single-ended zero feedback FirstWatt SIT1 monos and 1.5-way Zu Druid MkV augmented by the matching Submission sub. Our trusty Esoteric C-03 transistor preamp controlled SPL. Set to zero voltage gain, it acted as a passive, albeit with active buffers pre/post its attenuator for stable impedance regardless of setting. Even though the pre–>amps signal transferred via RCA regardless, I tried both the RCA and XLR paths between converters and preamp. In the Formula review, I’d noted something interesting. Despite the higher output voltage which a volume change compensated, the transformer coupling of the balanced outputs injected a viscous or ‘oily’ texture that was different from the drier RCA.

To be sure, this was a small matter. Still, it would appeal to different listener tastes. It made sense then to repeat the experiment when the optologic MkII had inherited the Formula’s XLR implementation. After I ran the first A/B sets off the Zu Event XLR cable to get a fix on the general scene, I followed up comparing RCA/XLR first on one deck, then the other. Had anything there changed in the new version? Here it’s vital to disregard propaganda. Many ‘balanced’ preamps run single-ended volume controls to not be balanced throughout. Certain XLR inputs are desymmetrized immediately. Etc. Whatever sounds better to you is better, period. No other explanation or justification is required. As always, trust your ears. It’s only them you must please.

Light wear? How much of a difference I’d hear was my primary question. The answer was surprisingly simple. Like those two words, it also sported two ‘s’: spatial specificity. The optologic circuit had more. It unraveled space with more exactitude. Images within the great wash of a given musical scenery were more tacit; as though the silences around and between them were deeper to increase contrast and individualization. In our audiophile lexicon, the catchphrase for it all is separation. A good visual for the effect would be to somehow punch up the value of negative space as the nothing that surrounds objects. It’s the eye’s equivalent for the ear’s ‘blacker black’. That routinely shows up in descriptions of effective powerline conditioners. Its primary playground are the spatial relationships between sounds. They organize into a three-dimensional acoustic map which we call soundstage. With it, sounds progress along the arc that transforms amorphous aural ‘somewhere’ clouds into precisely defined—shaped and sized—miniature events which are fixed with great certainty into given locations. Calling it holography exaggerates. Still, this progression as it is encapsulated by improved separation does move into the direction of that extreme quality. In short, the prime advance of the optologic upgrade had to do with creating more space within the tighter denser weave of the musical fabric which the tubes generate by design. Valve fanciers familiar with tube rolling could easily relate when one steps up from affordable Russian/Chinese 300B to Emission Labs or Elrog variants. Their greater refinement tightens up around the edges. Music doesn’t just flow. It simultaneously shows up as a structure. This structure is very specifically organized. The more this spatial organization grows apparent, the clearer become the underlying melodic, rhythmic and harmonic patterns and their complex interactions between the various recorded contributors.

Like punctuation choices, alternation of short and long sentences, emphasis from repeat first letters and other syntax elements, none of these things must be recognized to understand general meaning. One can read Shakespeare and follow along the emotions and actions of the protagonists just fine without any further recognition of the mechanics behind the bard’s craft. It’s simply that once elements of his craft enter our awareness whilst, back to hifi, we’re carried along music’s flow, we do so with deeper perception and appreciation. It’s a more conscious more illuminated experience than simple elemental drowning. It’s closer to observing architecture or tasting a complex dish and simultaneously seeing how it was done. It’s that extra dimension of participation which elevates our experience. And here the optologic La Scala MkII added more information to help that to happen. I could simply have written more resolution. But where’s the practical upshot in that?

Optologic tussle. Juxtaposing Formula to new LaScala MkII remained on the very same course but pushed closer to holographic lock. The sense of being (able to be) inside the music rather than watch it from just the outside was stronger still. At the extreme, it has us become a quasi performer like the actual musicians. Our participation is so immersive that for the duration, we nearly are a player ourselves. Because there’s more micro data to grab hold of and ride a tune with full involvement, our engagement is active, not passive. Not mere consumers, we become co-creators of our experience. A tech head calls it higher resolution and leaves it at that. He fails at explaining the benefits. And it’s not as though any machine could trigger or guarantee such depth. One still must show up for the experience with all one’s senses on high alert. If one does, this increased access to the musical innards then makes it easier, hence more likely to go deep. That’s the rationale for bona fide high-end gear. It’s also its curse. Because it makes access to music’s inner dimension easier, it quickly trains us to contribute less and less sensory intensity from our end. Soon our depth of experience diminishes. We become turned-off consumers who expect ‘do me’ magic with the push of a button. When magic refuses us, we blame soulless machinery and shop for still higher pixel count. After the initial hit of more raw data which supports easier engagement, we get lazy again. So endless upgraditis feeds upon itself like the Ouroboros.

But that’s separate from the machines. Where those go, the progression of LaScala MkII –> MkII optologic –> Formula was one of higher magnification. Whilst primarily about ambient recovery, hence audible space, there were the usual associated benefits for tonal sophistication relative to its decay action. Trailing fades get more and more ‘micro’ in a bleeding hurry. Obviously increased micro resolution pursues such fades with greater vigor. When such fades aren’t prematurely clipped off, the quality of timbre enriches and the progression of tones over time becomes more elastic and fluid, less choppy and metronomic. Though it’d be natural to presume that the MkII’s valve buffer had timbral advantages, in truth its primary quality versus the tube-less Formula was greater thickness. In a direct A/B, this manifested as minor opacity by contrast on the minus ledger; and as a perception of weightier dynamic transitions on the plus side. The nimbler flagship DAC exhibited the ripplier tiny waves called microdynamics. The ‘lesser’ optologic converter created the heftier macro contrasts. Viewed from a perspective of subjective speed, the Formula was a tad quicker, the LaScala more leisurely. None of it impacted actual clocking. The same tunes played back at exactly the same length of time. Still, a heavier denser less micro-concerned reading often feels just a mite slower.


Balance the balanced. Perhaps not surprisingly, the transformer-coupled XLR of the new LaScala followed in the footsteps of the Formula. They created a small textural difference to the RCA feed. This asserted itself independent of the subsequent signal path where our single-ended preamp desymmetrizes things internally. Users are thus encouraged to try both outputs regardless of voltage and theoretical correctness. If you can hear the difference, chances are you’ll prefer one flavour over the other.

Judgment juggle. As always, resolution enhancements in one stage of the hifi chain rely on sufficient downstream resolution to manifest fully. It’s an alternate meaning of balancing the balance. Put primitively, if out of 100 transparency points, one applied 80 to the source, 20 to the integrated amp and 0 to the speakers, the shiniest most capable new DAC wouldn’t really shine. Anyone upgrading from MkII to MkII Optologic must insure that the associated hardware is translucent enough to upstream improvements. Now the increased visibility of recorded space—that often subtle domain of gossamer reflections/reverb—and its influence on sophisticated tone with more generous decays will be obvious and well worth the conversion fee. Ditto for the more obvious organization of music into three-dimensional mapping, particularly so as music gets architecturally more complex. It’s testament to Cristian Anelli’s customer support ethos that the now middle model in their converter line benefited so rapidly from the R&D behind the flagship Formula and its FPGA-controlled discrete resistor ladders. It’s a very concrete benefit of Aqua’s modular approach. Existing owners get to enjoy the company’s IP advances without the usual sell/buy routine. Keep what you already have; bolt on real not cosmetic go-faster mods as they release. Anti obsolescence protects your valuable hifi investment with more current tech. Especially with fast-moving digital, the Joneses relocate a lot. Keeping up with them requires eyes glued on the ball. Aqua’s policy doesn’t drop it. That deserves applause. An already widely accoladed converter just became even better. It’s a most excellent place to invest your next upgrade grand into!