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November 2019

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Superior Audio Equipment Review

World Premiere Review!
Art Audio Quartet Vacuum Tube Monoblock Amplifiers
Three-dimensional sound staging and sense of scale that will capture your heart!
Review By Dr. Michael Bump


Art Audio Quartet Vacuum Tube Monoblock Amplifiers Review


  The Quartet mono blocks are among a varied line-up of top-shelf SET and Push-Pull amplifiers designed by master artisan-engineer, Tom Willis. Well-respected as one of the top valve designers in the UK, Tom established Art Audio in 1988. Along with a team of like-minded craftsmen, including long time friend, Chris Lucas, the company moved forward with the singular vision of maximizing the inherent musical qualities of traditional tube designs. After a brief hiatus, Art Audio was re-introduced to the US market earlier this year through a distribution agreement with Verdant Audio, Inc (Greenwich, CT).

In addition to power amplifiers, Art Audio offers state-of-the-art designs in preamplification, phono stages, the Phase 1 AC Power Supply/regenerator for turntable speed stability, as well as single and dual arm versions of the Composer Solo turntable (derived from the Claro Clarity 09 table, yet significantly expounded upon). The company also designs exceptional SUTs as well as interconnect cabling.

I was introduced to Art Audio many years ago via a colleague in the Columbus (Ohio) Symphony. Being fledgling audiophiles on a gigging musician's budget, we would often spend many post-rehearsal and/or performance evenings over craft beers in a favorite haunt in German Village. There we would discuss our latest LP find, or wax musings on what new audio design was destined to bring us closer to the recorded venue. On one occasion, Chris brought in a UK audio mag (can't recall which) with a photo and brief technical overview of the "new" Art Audio Adagio monos. Stunning images with these glorious KR T100 output tubes tastefully illuminated in a blue hue against an all-chrome chassis.

Hmmm... At the time, I wasn't entertaining the notion of SET amplification, as my ESS model 8's weren't really up to the challenge (although the Adagios produced a confident 50 Watts). Still, the you-are-there presentation that SET amplification is known for intrigued me (It should be noted that current production Adagios carry parallel 520B output tubes, running at 28 Watts per channel stereo). Through the years I've remained curious, though never had the occasion to actually hear a system powered by Art Audio designs.

Accessibility in the USA has been limited, until now. Fast-forward to this past April's AXPONA 2019, where I had the good fortune of meeting Verdant Audio's President, Scott Bierfeldt. Scott arranged an exceptionally sounding room with an array of impressive new Verdant monitors (designed by Scott), as well as several samplings of Art Audio pieces, including the Composer Solo turntable, Vinyl One Phono Stage, Conductor preamp, Quartet monos, Carissa Copper Reference SET, and Phase 1 Power Supply. To be sure, it was difficult to leave the room, but we did manage to arrange some quality home time with the Quartets for this review, with which I can say it has been an absolute pleasure, but again, difficult to part with.


Art Audio Quartet Vacuum Tube Monoblock Amplifiers Review


The Quartets are an 845 push-pull design, offering a 45-Watt drive, and with the high frequency extension of a 300B. Art Audio has enlisted a few internal design improvements since the initial Quartet specifications, among which are larger/better output transformers, two toroidal type input transformers – one for the low tension voltage heating circuits and one for high tension voltage tube plate circuits (This to provide separate fuse protection, as well as allowing for high tension time delay circuits on the primary windings), and a two-step standby switch located on the front panel (earlier models have this located on the rear panel). The Quartets are fitted with MKP capacitors and carbon film resistors. They also feature automatic biasing and have a solid state, twin choke, filtered power supply (The auto bias is set for 85mA @ 750V), as well as hand-soldered wiring throughout – no clip-ons. The ceramic tube sockets are excellent, providing some of the best grip I've seen.


Art Audio Quartet Vacuum Tube Monoblock Amplifiers Review


An exceptional advantage of acquiring a pair of Quartets, or really most any audio piece from Art Audio, is the ability to work with Tom in customizing many aspects of the build process. Standard upgrades include lums (glass tubes), ambience lights, legs, and chassis color (black or chrome). XLR inputs, additional impedance taps (4 and 8 Ohm are standard), and a preamp out can also be done. The amps ship standard with Shuguang 845A's, although upgrades to Sophia Carbon Plates or KRs 845 are an option. Scott informed me that Tom is working on a "Silver Reference" modification for all Art Audio triode-coupled monoblocks. This would mean an upgrade to silver foil capacitors and 5N point-to-point wiring (pricing TBA). Suffice to say that, because the amps are made to order, everything possible will be done to honor custom requests within the existing chassis.


Set up was a breeze, isolating both pieces in front of the house rack on two Timbernation platforms. Though I briefly used Kimber Kable speaker and single-ended cabling that Scott generously sent along, I spent the majority of my evaluation utilizing the house JPS Aluminata interconnects, power cables, and Superconductor 3 speaker cables. I set the Esoteric K-03 on repeat, walked away, and let everyone in the system get acquainted for a few days.

To begin with, let's go ahead and talk about that elephant in the room. Yes, these are drop-dead gorgeous to look at! They will turn every head that comes into the listening space. The soft blue light surrounding those gorgeous 845s set against a chrome background is over the top. These chassis generate a new aesthetic bar in late-night listening ambience. At times, I found myself distracted from listening, only to soak up the visual beauty of these instruments. To quote one of Art Audio's mantras, "Art for the Ears, Art for the Eyes." Ah yes well, on to the listening...!

Though I experimented with both taps, I found best results congruent with my Daedalus Athena's nominal impedance rating of 8 ohms. As mentioned in an earlier review of the Karan KA S400/KA L Mk3 combo, I love my Daedalus Athena speakers for a host of reasons, but one of them being that, at 96dB efficiency, you can basically run them with a flea Watt SET and they still sing like birds. Put some serious juice behind them, and they will respond like a chorus of nightingales! This was oh so true with the Quartets as, at 45 Watts, they could offer a beefy presentation with surprisingly tight and accurate low frequency support. Though the rest of the audio chain remained constant, I did spend a good deal of the evaluation A/B-ing the Quartets with my reference Merrill Audio Veritas. Vastly different designs, to be sure. However, the experience did provide for many ah-ha affirmations in favor of both.


Art Audio Quartet Vacuum Tube Monoblock Amplifiers Review


I will state again that, for only 45w, the Quartets pack a solid punch and stay in control, pushing out some amazing bass (to quote my initial listening notes, "Beefy low frequencies, though not bloated."). Additionally, anyone seeking that rare synthesis of classic euphoric tube midrange bliss and intimacy, upper frequency extension, firm and exceptional low frequencies, and scary holographic imaging and staging, need look no further than the Art Audio Quartets. Mate them with efficient speakers (such as the Daedalus Athena), and you will enjoy an exceptional audio marriage.

To be balanced, my initial listening noted a slight over-forwardness front/back with front stage sources – backline instruments at times seem unusually distant. On the other hand, stage width is impressive. No hint of smear or compression. Though individual imaging/source placement was initially a bit confused, this seemed to tighten up as the amps settled into the system.

Obviously when compared to the Class D Veritas, the Quartets didn't have quite the same transient speed/immediacy/sparkle. Not as much heft behind them, but of course, by design - Apples vs oranges here. Quartets also had some nominal difficulty getting the Athena to sing in full voice at lower amplitudes, with the highest uppers on certain reference recordings tending to roll off a bit. However, push the preamp up a few clicks, and their tactile flexibility came to life, giving you practically every nuance available in the recorded source. Again, bass in particular really sprang to life and filled out nicely. Ultimately, it's the three-dimensional sound staging and sense of scale that will capture your heart. The space and air the Quartets can provide between sources is also hard to beat.

Though they may not bring the scale of Mahler's Finale to his Second Symphony to your room (but then, my Athena aren't really voiced for full orchestra), they will bring the club or café in surreal ways. The intimate setting with singular or small ensemble acoustic sources is where you'll hear the Quartets at their best. Even though the Veritas can bring out the pop and sparkle with the best of them, they simply couldn't compare with the Quartet's visceral three-dimensionality. In particular, that tactile timbral realism of a small, live acoustic performance is an undeniable forte. Sure, the Veritas provide a slightly blacker canvas and certainly greater speed, but the Quartets draw you in, offering a stage to the innate human qualities of music performance.


A Few Reference Examples
Bill Evans Trio Waltz for Debby [SACD/Universal Japan SHM-SACD]
My "They're in the room!" moment came early in the listening sessions with this reference recording. This is the second (live) album cut from an afternoon session at New York's Village Vanguard jazz club in 1961. Those considered Bill Evans aficionados (I do not profess to be one of them) generally hold this and Sunday at the Village Vanguard as snapshots of the Bill Evans Trio at their best (in addition to the 1961 recording, Portrait In Jazz). As bass player Scott LaFaro was tragically killed in a car accident only 10 days following these recording sessions, both WFD and SVV serve as somber homage, though WFD seems to be a more balanced serving of selected titles. Much has been written as to the stunner this particular SACD pressing is. Suffice to say that, through the Quartets, I found the beautiful reflectiveness of this music all the more real and genuine.

The elements of decay in each envelope offered an anticipation of music to come. A continuing conversation and commentary on something so amazing, it defies traditional language. LaFaro's bass, though typically heavy in recordings such as this, is less so, warm, but with a greater presence to the transient characteristics of actuation. The same can be said of all three instrumental sources. Without exaggeration, the Quartets brought me to the gig. At times, allowing me to move the brushes myself over Paul Motian's snare drum, or stand over Evan's keyboard as he depressed each key.


Art Audio Quartet Vacuum Tube Monoblock Amplifiers Review


Rachelle Ferrell First Instrument  (CD/Blue Note)
Man, what a beautiful recording project! A reissue of her 1990 debut studio project, Somethin' Else, First Instrument is an audiophile's dream in both system/equipment evaluation and just simple listening enjoyment. No doubt, the Quartets greatly enhanced an already beautifully balanced presentation.
Given a similar repertoire of standards, there is some natural comparative interest with many other female jazz artist recordings, where one can quickly hear how Ferrell's unique and versatile treatment of her "instrument" stands alone. Alas, I only wish she had continued to pursue this genre more thoroughly/experimentally rather than crossing over to R&B.

One of my favs on the First Instrument recording is also one of the shortest (literally and figuratively!), "Inchworm" (Just for kicks, I enjoyed running back/forth between hers and Patricia Barber's rendition!). Lenny and Rachelle create a fantastic call/response scat intro that was completely palpable via the Quartet's energy. The subsequent synthesis bet. human voice and instrument is wonderfully represented when Shorter and Ferrell cut loose. Its only when they converge on the highest frequencies of their respective ranges that one hears a slight roll-off/roundedness. The raw talent and versatility of Ferrell's craft comes to bear in the live version of "Autumn Leaves," the Quartets enhancing a realistic stage and reflection of venue. Add a knock-out line up of first-call musicians such as Wayne Shorter, Stanley Clarke, and Lenny White, and this track sends chills from beginning to end.


James Taylor Before This World [Concord Music Group CD]
For as much as I enjoy critical listening and have embraced the music of James Taylor for most of my life, it's strange to realize I've never used one of James' recordings as a point of reference. Better late than never, I suppose, and Before This World provides an excellent example. Besides, one of my dear college friends, Andrea Zonn, is with the band, backing vocals and playing a mean fiddle! The opening track, "Today, Today, Today," keeps this project grounded in its country and blues roots. It's a great welcome to the listener of the immense talents gathered in this project (James aptly bills this gathering of friends as "The All-Star Band").

The mixes are all hot, putting James front and center, yet a clean path is carved right down the middle to allow a crystal view of everyone in the band. The title track, in duet with Sting, is presented almost as a prayer, in all the quartal harmonic splendor of Gregorian chant, while allowing a wide frame for James' quintessential picking style. In spite of the fact there were moments when I longed for the heft, pop, and punch of the Veritas, particularly when Steve Gadd wanted to bring it, the Quartet's forte of visceral three-dimensionality is very much in spades throughout this recording.


Skywalk The Bohemians [LP/MCA-Zebra]
Though I spun other LPs with the Quartets, this one remains one of my eldest references. Back in the 80's, I was obsessed with this little-known Canadian fusion group (Many may recognize one of the tunes, "Jesse James," as an early background for the Weather Channel). Killer talent in every position of the band, combined with outstanding recording and engineering skills behind the board. Kat Hendrikse, in particular, masterfully dialed in an excellent electro-acoustic synthesis of drum kit and early experimentation with loop patches and real-time samplings via Linn Drum programming. "Grandstand" and the title track stand out as spotlights to Hendrikse's virtuosity. But again, talent abounds in all directions within the group, with this recording really giving your system a ride. The Quartets held their own against the Veritas in demonstrating the frequency extremes of "Grandstand." Only a slight bit thin or strident in the extreme uppers, yet otherwise the music never sounded bloated or unfocused when dipping low. Another testament to the amazing bass these amplifiers can provide!

The sense of stage within this recording was something I never fully appreciated until hearing with the Quartets. Crystal clear source placement, space, and depth were outstanding. The closing track, "The Torchbearer," had all the subtle, nostalgic late-night 80s jazz seductions that one might hope for. Again, and without sounding too cliché, just try closing your eyes and not feeling the band in the room... If you have not already been hypnotized by those beautiful blue chassis lights!


Art Audio Quartet Vacuum Tube Monoblock Amplifiers Review


Closing Credits
Spending quality time with these Art Audio Quartets has been an absolute pleasure, and again, difficult to part with. These are truly audio investments of a lifetime for the discerning listener. They do indeed draw you inward to the recorded moment, offering a stage to the human qualities of music performance. Congratulations to Tom Willis and his team on an outstanding design among many in the Art Audio offerings. I must be completely honest in admitting I am indeed tempted beyond my bank account with these. Stateside, Scott Bierfeldt at Verdant Audio was more than generous, and I thank him for the opportunity. Do yourself a favor and take these for a test drive.

Quality time guaranteed!



Reference System
Preamplifier: VAC Signature MKII SE (w/ phono)
Amplifier: Merrill Veritas monoblocks
Digital Source: Esoteric K-03
Analog Source: VPI Scoutmaster Signature (w/ Dynavector XV-1s cart)
Speakers: Daedalus Athena v.2
Subwoofer: Velodyne DD10+
Cables: JPS Aluminata power cables / interconnects (XLR & RCA), JPS SC3 speaker cables.
Also Sampled: Kimber Kable VS Series speaker cables, Kimber Kable Timbre RCA interconnects
Power Conditioning: Running Springs Haley





Sub-bass (10Hz - 60Hz)

Mid-bass (80Hz - 200Hz)

Midrange (200Hz - 3,000Hz)

High Frequencies (3,000Hz On Up)



Inner Resolution

Soundscape Width Front

Soundscape Width Rear
Soundscape Depth Behind Speakers

Soundscape Extension Into Room


Fit And Finish

Self Noise

Value For The Money




Type: Vacuum tube stereo amplifier
Power Output: 45 Watts per channel stereo
Vacuum Tube: Push-Pull 845 power tube, plus ECC 82 and 12BH7 for driver
Frequency Response: 10 Hz to 65 kHz
Input Sensitivity: 700mv
Input Impedance: 180kOhm
Output Impedance: 4 and 8 Ohm
Circuit Negative Feedback: 6dB
Tube Biasing: Automatic 
Rectifier: Solid-state
Chassis Colors: Black or silver
Price: $13,999, as reviewed $17,599



Company Information
Art Audio UK Ltd.

Voice: 0115 963 7795
E-mail: sales@artaudio.co.uk 
Website: www.ArtAudio.co.uk



USA Distributor:
Verdant Audio, Inc.

Voice: 475.350.9876
E-mail: info@verdantaudio.com
Website: www.ArtAudio.us















































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