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Viola Audio Laboratories Crescendo Preamplifier and Concerto Power Amplifier

Viola Audio Laboratories Crescendo Preamplifier and Concerto Power Amplifier

It’s both rewarding and disconcerting to regularly discover fabulous albums that have been around for decades yet remained unknown to you until some chance encounter brought them to your attention. The “rewarding” part of that statement is self-evident; the “disconcerting” part is the realization that there must be many other such gems out there that you will never chance upon, but that you would also consider essential.

The same could be said about high-end audio manufacturers. Right at this minute there must be many amazing-sounding products that I’m completely unaware of. There are so many companies and so little time to sample their products that it’s natural that some firms fall off the radar for years—until a chance encounter compels further exploration.

It was just such a chance encounter that led me to this review of the Crescendo preamplifier and Concerto power amplifier from Connecticut-based Viola Audio Laboratories. During a trip to France a couple of years ago to tour Focal and Micromega I visited the home of Micromega’s owner where I heard an extraordinary system of all-Viola electronics driving the Kharma Exquisite Extreme Grand loudspeakers (with Kharma’s massive subwoofer thrown in for good measure). The sound was spectacular in every way. The system’s owner, who was not bound by price constraints, considered many electronics brands before choosing Viola. (The company apparently enjoys a strong reputation in Europe and Asia despite its low North American profile.) At the time, I knew almost nothing about Viola and had never heard its products.

Six months later at the 2013 Consumer Electronics Show I had another positive encounter with Viola, this time with its Crescendo and Concerto preamplifier/power-amplifier pair. The products’ user interface was unlike any I’d seen before, and the new units, while not inexpensive at $22,000 each, were priced lower than other products in Viola’s line.

At the show I also learned about the background of the company’s founders, Paul Jayson and Tom Colangelo. They had been designers at the original Mark Levinson Audio Systems company in the late 1970s, and had contributed to many of that company’s landmark products. In 1984 when Mark Levinson left to form Cello, Jayson and Colangelo went with him. With Jayson as Engineering Manager and Colangelo as the head of R&D, they comprised the engineering team behind that company’s highly regarded offerings, including the Audio Palette, which remains the best product of its kind every created. Cello folded in 2000, leading Jayson and Colangelo to form their own company, Viola Audio Laboratories. Colangelo passed away in 2007 after 30 years designing high-end audio, 27 of them with Jayson.


The Crescendo and Concerto look and operate unlike any other electronics I’ve seen. The identical chassis have no apparent front- panel knobs or controls, just a small truncated-pyramid-shaped display with nothing more than a few symbols illuminating it. The minimalist look is possible because the system is controlled via an included iTouch and dedicated Wi-Fi network. Power-on and -off, source selection, volume, muting, and other functions are all made through the iTouch. The units are supplied with a pre-configured Wi-Fi router that can be plugged into any AC socket within Wi-Fi range. The Crescendo and Concerto are connected by an Ethernet cable, but get their instructions from the iTouch wirelessly via the router.

Via the iTouch interface you can change the display color (globally or by selecting a different color for each input), apply 10dB of attenuation on select inputs, name the inputs, monitor the heatsink temperature, and access other functions beyond those found on traditional remote controls. In practice, I appreciated that the iTouch liberated me from requiring a line- of-sight between the remote and the equipment rack. Of course, Viola’s remote app will run on any iDevice. As much as I like the feel of a heavy machined remote, the iTouch proved a welcome change in daily use. If the iTouch is out of power, the Crescendo and Concerto can be operated by the rudimentary front-panel display. The Crescendo’s display has power and volume up/down controls, and the Concerto a power on/off. These displays are contained within the small “V” shape cut into the front panel, which extends to the top plate and the back of the unit.

The chassis are machined from solid blocks of aluminum and have a monolithic look. Ridges are cut into the top plates that suggest heat sinks, but without the fins and sharp edges.

The power amplifier, housed in an identical chassis, has within this top-plate groove an unusual heat sink integrated into a slot running down the middle of the chassis. The metal work is gorgeous—as good as it gets. Moreover, the aluminum is anodized with a slightly grayish patina that gives the Crescendo and Concerto an elegant, yet businesslike vibe. The visual effect of the whole package is stunning.

The Crescendo is the second model up in Viola’s four- preamplifier line, and the only one to incorporate a digital- to-analog converter. In addition to digital inputs on USB and SPDIF, the Crescendo offers analog connectivity via three balanced and three unbalanced analog pairs. The output choices include balanced or unbalanced connection. The DAC can accept datastreams up to 192kHz/24-bit, with the sampling frequency and word length displayed on the iTouch.

The circuit is based on Viola’s discrete operational-amplifier module. Op-amps needn’t be integrated circuits; they can be built from discrete components into a module that functions as an op- amp but without the sonic compromises of an integrated-circuit op-amp. Viola’s discrete op-amp is built from a low-noise FET input stage, a differential voltage-gain stage, and a low-output- impedance voltage follower. Volume control is realized with a discrete thin-film-resistor network controlled by switches (in 1dB steps—2dB steps below -50dB). The integral DAC section is built around an XMOS processor running on Viola’s own clock circuit and a BurrBrown PCM1794A DAC. The DAC section had no trouble locking to any sampling frequency and word length I fed it. Finally, the power supply is housed in a separate subsection within the monolithic chassis.

The Concerto is the entry point in the Viola power-amplifier line, with four models above it. The amplifier delivers 100Wpc into 8 ohms, and commendably, can double that output power into 4 ohms. The dual-mono design extends to the power supply, which employs a choke just after the transformer. This technique, developed many years ago for Cello products, is deployed throughout the Viola line. According to designer Paul Jayson, the choke smoothes the current spikes that charge the reservoir capacitors, keeping them more fully charged at all times. It’s intuitive to think of a power supply as drawing current from the wall on a consistent basis, but in fact current is pulled from the wall in spurts during the peaks of the 60Hz AC power waveform. The choke, with its inherent energy storage, spreads this energy out over a longer time and keeps the capacitors fully charged between the peaks in the 60Hz AC waveform. Incidentally, the power supply for both the Concerto and Crescendo automatically configures the transformer for the correct line voltage.


The Concerto’s output stage is built around a fairly new transistor technology from Motorola called ThermalTrak. The transistors have five leads rather than three, and incorporate a diode within the package that reacts to the transistor’s temperature. Specifically, the voltage drop across the diode changes with temperature, and this voltage drop fine-tunes the bias current on a moment-to-moment basis. Viola has taken this idea to the next level by including a microprocessor that adjusts the overall bias level within which the ThermalTrak system makes fine, short-term adjustments.

The only chink in Viola’s armor is its woefully inadequate owner’s manuals. Products of this price, sound quality, and execution deserve professionally written and produced documentation, not a few photocopied pages inserted into a plastic Office Depot cover that falls apart. More importantly, the quality of the writing and the organization of the contents of the manual are sadly lacking. For example, the first two sentences of the “Quick Start Guide” are: “Prior to crescendo version, any crescendo leaves the Viola facilities with the default factory setup to create its own network named ‘crescendo’ and assumes a network IP of with an IP mask of On a point to point network on versions prior to, all IP addresses on the network are to be static.” This doesn’t appear buried in the back of an owner’s manual, but is the first paragraph on the first page of the Quick Start Guide. Oy.

The owner’s manual, however, is a microcosm of a larger picture I garnered of a company that is totally engineering driven. Viola has no consistent look among its products, offers only very-high-end preamplifiers and power amplifiers (no integrated amps, CD players, DACs, or other products to “round-out the line”), has never pursued the entry-level or even mid-level customer, seem to relish its low profile in the market, never advertises its products, and creates the kinds of components Jayson is interested in designing rather than what the market asks for. The picture that emerges is of a designer, Paul Jayson, who has dedicated the last 35+ years of his life to perfecting cutting- edge amplification circuits—to the exclusion of all else.

But as we’re about to discover, that path has its own glories.

I hinted in the introduction that these Viola products were quite a discovery, and indeed they are. Starting with analog input signals (we’ll get to the Crescendo’s DAC performance later) from a dCS Vivaldi or Basis Inspiration/Air-Tight PC-1 Supreme/Simaudio 810LP, the Viola pair was startling in its speed, transparency, and resolution. Instruments and voices were right there, vivid and alive in ways that rivaled any amplification I’ve heard. The treble, in particular, had a realism and tangibility that were simply sensational. This was the result of an extreme transparency and clarity that seemed to strip away all sense of anything imposing itself between me and the music. Listening to music through these electronics was like taking one significant step closer to the original performance. Here’s an analogy. I live near the California coast and walk every morning. When I leave the house the rolling hills and vistas are often softened by a light shroud of moist ocean air. By the time I get back and the sun has ascended and burned off the moisture, the same landscapes appear more vivid, with greater clarity of detail and a richer, denser color palette. That’s what the Viola electronics sound like; lifting the electronic haze renders an immediate increase in clarity and palpability.

This quality was particularly pronounced in the treble, which was simply sensational, among the best I’ve heard from a small handful of the best electronics. I’ve been listening lately to a terrific hybrid SACD from 2003, Roy Haynes’ Love Letters with Christian McBride, Dave Holland, David Kikoski, Kenny Barron, John Scofield, and Joshua Redman. It’s a musical triumph, made all the better by the stunningly great sound quality (it’s an original DSD recording). The Viola electronics rendered Haynes’ cymbal and snare work with such clarity and precision that they fully conveyed the measure of his genius. He creates very fine gradations of dynamic expression that perfectly complement the melody or the soloist’s expressions. Moreover, the drums and cymbals have a sonic tangibility that’s breathtaking. I heard a new wealth of subtle inflections and nuances in his performance through the Viola electronics, not to mention a far more convincing illusion of the drum kit appearing in my listening room. The top end was finely textured and highly nuanced, conveying a fresh abunance of inner detail.


This brings me to another of the Concerto and Crescendo’s great strengths, its rendition of transient information. These electronics are lightning-fast—Spectral and Constellation fast— yet they have no artificial etch that would impart a mechanical or sterile character to the sound. The Viola reproduces transient sounds the way instruments do in life, with sometimes startling attacks and quick decays. Some electronics can sound fast through the treble, but exhibit a kind of discontinuity because the midrange speed doesn’t match that of the top end. The Viola electronics totally avoid this pitfall. In fact, they exhibit a degree of transient coherence, from top to bottom, that is as startling in its sonic achievement as it is in the musical result. Drums fairly jump from the presentation. Even low-level transients sound highly realistic through the Viola. Midway through Joe Pass’ great solo on “Contractor Blues” from the LP 88 Basie Street, the drummer sets the rhythm with gentle rim shots. Through the Viola these are not just undifferentiated transient noises, but instead sound like wood hitting the rim of a snare drum.

This transient performance served piano particularly well, highlighting the fact that the piano is a percussion instrument. The explosive dynamics from, say, Bruce Katz’s instrument on the superbly recorded AudioQuest CD Crescent Crawl or Minoru Nojima’s Hamburg Steinway on Nojima Plays Liszt were nothing short of sensational. Again, this electrifying transient speed was not the result of an artificial hype that quickly grows tiring. Rather, the Viola electronics simply had the speed and wide dynamic envelope of the real thing.

Speed, resolution, and transparency are often accompanied by a tendency toward leanness, lack of body, thinning of tonal colors, and a bottom end that favors precision over visceral weight. That was not the case with the Concerto and Crescendo. In addition to a full-bodied tonal balance, the Viola pair’s bass was phenomenal. These electronics combined deep and effortless extension at the extreme bottom with a visceral muscularity in the midbass that created a powerful physical involvement with the music. The huge left-hand chords in the previously mentioned Nojima Plays Liszt were thunderous and spine-tingling. The Concerto seemed to have an iron-fisted control over the Magico Q7’s woofers, showcasing this speaker’s remarkable combination of pitch precision, lack of overhang, extension, and sheer bottom- end verve. Despite its rating of “only” 100Wpc, the Concerto sounded like a powerhouse, with no softening of bass drum impact at high playback levels or any sense of dynamic compression. The only other amplifiers I’ve heard in my own system with this quality of bass were the Jeff Rowland 725 monoblocks I reviewed in Issue 228.

These impressions were made listening to the Concerto and Crescendo being fed analog signals from a dCS Vivaldi, Aesthetix Romulus CD player/DAC, and my LP front end. How does the Crescendo’s integral DAC sound? I connected my MacBook Pro running iTunes and Pure Music to the Crescendo via USB, and alternately to the dCS, and Aesthetix, with the dCS and Aesthetix feeding the Concerto’s balanced analog inputs. I found the Crescendo’s integral DAC to be excellent, but not at the same level of achievement as the Concerto and Crescendo’s analog circuits. The Concerto and Crescendo are so good that anything less than a superlative source prevents them from achieving their full potential. The Crescendo’s DAC was fairly dimensional, clean in timbre, and wide in dynamics, but it did impart a bit of hardness and sheen to the treble, along with a reduction in transparency and immediacy. The exquisite, finely filigreed top end which sets these electronics apart as special was still apparent, but not to the same degree as when the Crescendo was fed an analog signal from the Aesthetix or, especially, the dCS. If the Crescendo and Concerto weren’t so spectacular, the DAC wouldn’t have come under such a critical ear.

The Viola Audio Laboratories Crescendo and Concerto are simply stunning musically, and among the best electronics I’ve heard. The transparency, the sense they convey of nothing coming between you and the music, their sensational treble resolution without a touch of the analytical, their wide dynamic expression, and their absolutely sensational bass vault the Viola electronics to world- class status.

Throughout this review I’ve felt the urge to temper my praise of these electronics only because these are the company’s “entry- level” components—what are Viola’s $69,000 Spirito preamplifier and $59,000 Legacy 100W pure Class A monoblocks capable of? It’s mind-blowing to consider that one of the following statements must be true: 1) the Crescendo and Concerto are very close in sound quality to Viola’s reference-level products; or 2) Viola’s top- of-the-line electronics are in a league that I’ve never experienced.

Whatever the case, you should seek out and listen to these extraordinary electronics for yourself. Viola products may be difficult to find, but you may consider them to be as great a discovery as I do.


Inputs: Three balanced on XLR jacks, three unbalanced on RCA jacks, one SPDIF, one USB
Outputs: One balanced on XLR jacks, one unbalanced on RCA jacks, tape-out on RCA jacks
Network connection: Wi-Fi
Viola Local Network (link bus): CAT-5
Gain: 16dB or 26dB (switchable)
Supplied accessories: Apple iTouch, pre-configured Wi-Fi router, Ethernet cables
Dimensions: 17.5″ x 3.5″ x 15″
Weight: 25 lbs.
Price: $22,000

Concerto Stereo Power Amplifier
Power output: 100Wpc into 8 ohms, 200Wpc into 4 ohms
Inputs: One balanced on XLR jacks, one unbalanced on RCA jacks
Viola Local Network (link bus): CAT-5
Dimensions: 17.5″ x 3.5″ x 15″
Weight: 53 lbs.
Price: $22,000

By Robert Harley

My older brother Stephen introduced me to music when I was about 12 years old. Stephen was a prodigious musical talent (he went on to get a degree in Composition) who generously shared his records and passion for music with his little brother.

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