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Equipment Review

October 2004

Nightingale ATS-90 Mono Amplifiers

by Tim Aucremann

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Review Summary
Sound "Cover all the desirables and then some" -- great speed, soundstaging ability and "tonal depth"; but "no one aural attribute stands out at the expense of others"; "let you hear deeply into tonal structures that ultimately breathe life and immediacy into the music."
Features "The ATS-90 is a pure class-A amplifier using a push-pull topology to deliver 90 watts with a frequency response from 10Hz-45kHz. A Sovtek 6922 dual-triode amplifies the input signal. This is coupled to a single Phillips JAN 6189 phase splitter that provides low-impedance input to six NOS Phillips 7581A power tubes."
Use "After initial power-up, I never turned these amps off, preferring to use the Standby setting that allows them to reach proper thermal conditions within ten minutes." "The tubes are biased electronically -- there are no manual adjustments."
Value Their $12,595 price "pushes the ATS-90s into cost-no-object, super-amp territory," but their "aesthetic has an easy-on-the-eyes, timeless character, and the ATS-90s' performance is wholly satisfying."

He lived in a porcelain palace -- the most remarkable in all the world. And when the Emperor of China took a stroll, he walked paths lined with flowers, silver bells upon their stems. Beyond the gardens lay a noble forest with lofty trees, and beyond these, boats of fishermen toiled the waves at evening tide in a sea of deepest blue. As they spread their nets on moonlit nights, the fishermen could not help but stop their work to hear the most wondrous of sounds. In the trees offshore there lived a tiny gray bird, a nightingale, who sang to them her beautiful song.

The nightingale came willingly when she learned the Emperor wished to hear her. In the center of the great hall she sat upon a golden perch and tears came to the Emperor’s eyes as her song touched his heart. Offered great honors, the nightingale declined. "I have seen tears in the Emperor’s eyes," she said. "That is my richest reward." Twelve servants were appointed to attend her. She sang willingly whenever called upon, though her leg was bound by silken string and she was allowed to leave her cage but twice a day.

One day a package arrived from across the sea. It contained a mechanical nightingale covered in jewels, and when it was wound it sang as truly as the living. Replaced by the jeweled bird and unhappy in captivity, the nightingale escaped to the forest where she sang again for the farmers and fishermen. For the song to be sweet, the singer must be free. On his deathbed the emperor heard the call of the nightingale and went into the forest where her singing restored his life.

But what of the artificial nightingale that matched the real bird note for note? The ancient scrolls tell us little. That might be another story. Or perhaps it is this one.

Show us your bird!

Nightingale audio products are manufactured by Simetel Corp., an Italian firm based in Rome. Founded in 1959, Simetel’s primary work is in the field of professional and military telecommunications. Their expertise in telephones and computers brought a solid understanding about the negative effects of electronic noise on sound definition. In 1995, a shared passion for music led a small group of engineers and technicians to begin building high-definition audio products, and the line now includes amps, preamps, speakers and line conditioners. The Nightingale brand is successful in Italy and growing in Europe. It is relatively obscure in the US, but I expect that to change once more audiophiles get a chance to experience Nightingale products.

The Nightingale ATS-90 is a mono amplifier that measures 14 1/2"W x 9"H x 19 3/4"D and weighs 70 pounds. A pair arrived at my door, each in its own sturdy wooden shipping crate. The amps were intended to be nestled protectively in their boxes but, alas, the rigors of cross-country shipping played havoc with the heavy contents as they shifted against their rigid but crumbly Styrofoam packaging. Upon initial setup neither amp proved functional. A few quick e-mails led to diagnosis and an easy fix. Transformer connector plugs on the primary circuit board of each amp have an inverted mounting and had loosened in transit. After removing the amp’s top cover, and loosening the screws on the main board to reach its underside, I easily reattached the plugs.

Nightingale’s cordial designer, Luciano del Rio, assures me that future releases will have all plugs secured to their sockets. As the Hans Christian Andersen fable teaches us, you can’t always possess what you love -- but for those who can afford a pair of ATS-90s at $12,595 USD, expectations will be high. Simetel states that its products are constructed under ISO 9001 QA standards, and for the remainder of their visit, the amps performed flawlessly.

When I think Italian I think beautiful design, and the Nightingale amps do not disappoint. Each cabinet is made from solid walnut with a metallic, champagne-colored non-conductive top panel. Gloss-black-enamel transformer covers sit behind the tube array. The tubes are exposed, so you’ll want to give the amps plenty of breathing room. White ceramic tube sockets are a nice visual touch. The front is adorned with a single knob with indents for On, Standby and Off. Backside fitments include large WBT 0763 speaker connectors for ground and both 4 and 8 ohms, along with an IEC power-cord socket and single NUVAL RCA input. I was struck by the understated, almost organic elegance of the Nightingale amps, especially compared to amps that look like black metal boxes.

According to Simetel, the ATS-90 is a pure class-A amplifier using a push-pull topology to deliver 90 watts with a frequency response from 10Hz-45kHz. A Sovtek 6922 dual-triode amplifies the input signal. This is coupled to a single Phillips JAN 6189 phase splitter that provides low-impedance input to six NOS Phillips 7581A power tubes. The 7581A is an industrial-strength version of the 6L6GC. Electronically stabilized anodic and 6922 filament voltages aid tube life and improve signal-to-noise ratio. A minuscule 2.5dB negative-feedback loop reduces distortion. The tubes are biased electronically -- there are no manual adjustments.

Aside from the loose-plug glitch, setup was happily simple -- no manual is included. Install the tubes and generic power cords, connect the cabling, and go. For critical listening sessions, I like to let tube amps warm up for at least half an hour. After initial power-up, I never turned these amps off, preferring to use the Standby setting that allows them to reach proper thermal conditions within ten minutes. On fire-up, each 7581A exhibits a hazy blue aura surrounding the tube.

The bird cage

The majority of playback for this review originated from a Teres 255 turntable with SME V tonearm and Shelter 901 cartridge. An FMS Blue II cable connects the tonearm to a Camelot Technologies Lancelot Pro phono stage. Since my last review I mounted the Teres on a large 20"x 20" x 3" maple block from Tony's Woodshop, which in turn sits on Mapleshade Isoblocks. This combination of large maple block and Isoblock feet gets my vote for the biggest-sonic-payback-for-little-wampum audio tweak. It lifted the entire soundstage off the floor, improved the Shelter’s already fine bass definition, and generally yielded more information from the grooves. If you’re among the vinylista who want an inexpensive way to learn the value of turntable isolation, try this setup.

The phono stage feeds a Conrad-Johnson Premier 16LS preamp to drive a Conrad-Johnson Premier 140 amplifier. The 16LS sits on Walker Valid Points, which in turn rest on Art Audio Q-Dampers. The front-end analog chain uses FMS Zero cabling. The Premier 140 drives Audio Physic Avanti Century speakers via Shunyata Lyra speaker cable. Speakers sit in the middle of my 18' x 22' x 10' listening room in the recommended Audio Physic configuration. Red Book playback arrives via a Parasound 2000 CD player mounted on Symposium Rollerblocks and connected to the Premier 16LS with Shunyata Aries interconnects.

Lacking a matching brace of golden perches, I placed each Nightingale amp on a custom maple amp stand from Mondo Designs spiked into the floor. An original six-port Shunyata Hydra hosts all electronics; however, for this review, amplifiers went straight into the wall sockets.

Nightingale, sing us a song

I had no idea what to expect from the ATS-90s -- no one I knew had ever heard of them, much less listened to them, and the distributor said the pair sent to me was the first in the US. I didn’t even know exactly what they cost. But it did not take long for my early listening sessions to give way to the obvious -- these amps cover all the desirables and then some.

Frankly, during these initial listenings it was hard to take notes, to be analytical -- the ATS-90s drew me away from themselves and toward the music. What that told me is they have neither obvious flaws nor emphatic characteristics, deflecting attention from themselves without singular distinction. They are well balanced and eminently listenable.

However, to say no one aural attribute stands out at the expense of others is not to say the ATS-90s are without virtues. Audio Physic speakers are renowned for their capacity to establish a precise soundstage. If a component placed into my system has any weakness in this area, it is immediately noticeable. I’m not a soundstage nut; it’s just the price of admission. Listening to "Homeless" on Paul Simon’s Graceland [Warner Brothers 25447-1], the amps accurately laid out the Ladysmith Black Mombazo singers in an arc -- speaker to speaker, yet behind the speakers -- with Simon in the middle and just slightly to the front. Each singer’s voice is clearly individuated within that arc and much to my delight, the Nightingale amps reveal each singer’s voice inflections and subtle note bendings. The original London-cast recording of Charles Strouse’s Nightingale [Polydor 820 248-1 Y-1] portrays each singer nicely arranged -- close your eyes and see the stage, with individual players moving credibly upon it in three dimensions -- across, fore and back. Though created at Abbey Road studios, the performance is presented as it would sound on stage.

One of my de rigueur reviewing albums is Kraftwerk’s Electric Café [EMI EMD 1001]. On "Telephone Call," the ATS-90s gave me the classic audiophile experience of "hadn’t heard that before!" Electronic instruments electronically controlled can generate astonishing transient snap, and I’ll confide that the ATS-90s are perhaps the best-regulated, fastest-sounding tube amps I’ve heard. And yet these electronic notes were so exactingly precise and clear. It was as if time slowed and I could hear harmonic detail across the leading edge of a transient, then bzzzt -- in an instant it’s gone, into the black. Beyond notes popping in and out of space, zipping three-dimensionally about the soundstage, I heard the incredibly tight control the band has on reverb -- applying it as if reverb were itself a musical instrument. And for the first time I had the sense of Kraftwerk as individual musicians playing instruments.

Throughout my reviewing sessions I was mesmerized by the limpid tonal presentation of the Nightingale amps. "Clarity" seems a simple enough term, and while true regarding the ATS-90s, it doesn’t quite describe what I’m after. We audiophiles have oft heard (perhaps too oft) discussions of tonal purity. Not blessed with perfect pitch I can’t say the ATS-90s display tonal purity, but they do yield what I’ll call tonal depth. And across the Nightingale amps’ many strengths, if some are more equal than others, this goes near the top of the list. To mix metaphors -- you "see" deeply into a tone as it begins, unfolds and dies within time -- that twenty-hand-rubbed-coats-of-carnauba kind of richness. To cash out tonal depth in other terms, I could say it is the harmonic (or inharmonic) richness of a sonic meme across time. Got that?

In quiet passages, drummers often mark a beat by laying a drumstick across a snare with the stick’s head resting on the skin and the other end on the snare’s rim while striking this drumstick with the other -- wood on wood with empathetic vibrations into the drum head. To give an example, I’ll choose an album you may know. Consider the title track from Dire Straits' Brothers in Arms [Warner Brothers 1-25264]. The ATS-90s present each stroke precisely. You hear the initial snick as one stick bites into the other, then the resulting resonance through the stick into the drumhead and the air within, and then it fades away. It happens very fast. I sensed this tonal depth on hearing the sonic variation between one drumstick striking the other slightly closer to the rim versus closer to the drumhead. These are fine-spun differences, yet the ATS-90s pull them from the groove to give an incredibly realistic picture of a musician at his instrument. And the Nightingale amps let us hear how the drummer’s beat takes on a different overtone when one stroke is harder than another. The faintest of high-hat touches have a crisp initial strike as wood meets brass, then a satisfying resultant tizz and decay. You can hear the decay from the Hammond Leslie horns rotating in their cabinets for what seems like forever after finger is lifted from keyboard. Amid everything else going on in the tune, wherever your ear is drawn, the Nightingale amps let you hear deeply into tonal structures that ultimately breathe life and immediacy into the music.

Consider this almost-molecular level of sonic complexity as revealed in a single drum stroke applied en large as a capacity to define and reveal differences among instruments, voices, and entire orchestral sections. On Finzi’s Intimations of Immortality [Lyrita SRCS 75] I heard layers upon layers of voices, each choral line clear and distinct against the backdrop of the orchestra. I sensed both individuated and multiple choristers standing together, diaphragms controlling air. I knew these were people standing and singing together, wholly lacking that unpleasant discontinuous presentation of bodiless floating heads. Bass runs are tonally and temporally distinct -- no sluffy, one-note bass here. Marimbas, triangles, and shaken bells are rich in harmonic detail. Clarinets and flutes are breathy yet focused as each holds fast to its position in space. I hear that flutey metallic sound of air across an open hole in metal -- a quality rarely captured by all but the best equipment. Instruments of similar timbre become delightfully differentiated -- yes, even trumpets and cornets.

As hinted at above, when listening to music without thinking componentry, the Nightingale amps gave me a sense of time slowing down. They allowed my appreciation to wander between taking in the whole and following different portions of an orchestra across a complex piece as the composer lets each section receive its due. For a big piece with lots of movement, consider the excellent 45rpm Speaker’s Corner reissue of Mendelssohn’s Third Symphony, the "Scotch," along with a side devoted to "Fingal’s Cave" [Decca SXL 2246]. Ambience abounds. Textural sweeps across sections are fleshed out with the air and definition of massed strings and immediately you know this is an orchestra in space in a hall. Woodwinds burble up the leading edge of an orchestral swell. One hears lower-frequency undercurrents as a well-delineated substructure supporting lots of movement. Basses are light and fast -- not light in weight, but quick and distinct. The ATS-90s yield depth of tone with delicacy of touch. Celli playing pizzicato are gorgeous.

Draw your ear to where you will -- the music is there. Lines from instruments and sections are easily followed. I think to myself that Mendelssohn’s Third must be a fun piece to play; everybody gets a workout. And all the while there is an easy flow of continuity -- the Nightingales hold it all together across the frequency spectrum, no sonic character conspicuous by its absence nor spotlighted in overemphasis. I never had a sense of the amps breathing hard, their 90 watts drawing from a deep well.

Comparo de Janiero

I’ll use the $7000 Conrad-Johnson Premier 140 stereo amp for comparison because, at the moment, there are no other $12,000 tube amps lying about my listening room. Doesn’t it just irk you when company comes and you’re caught short of five-figure equipment?

I heard no sonic surprises. Listening to "Canzone e Danze," the third piece in Resphigi’s Brazilian Impressions [Mercury Golden Imports SRI 75023], you immediately realize that Nightingales buy you a seat much closer to the orchestra. They are more forward, but not brighter -- they simply bring an impressively natural focus and clarity. Throughout my listening sessions when switching to the Premier 140, I found myself turning up the volume four or five clicks to approximate the same output I heard from the Nightingale amps.

Both amplifiers do a top-notch job of throwing a three-dimensional soundstage with back- and side-wall ambience in abundance. Oddly enough, soundstage width varied between the two amplifiers with the recording. In the first part of Resphigi’s composition -- the "Notte Tropicale" -- there is a tambourine player who, with the Nightingales, sounds like he is back, back, back behind the rest of the percussion, and yet his instrument displays an almost count-the-clappers authority. The same tambourinist rejoins his section when heard with the C-J amp. The Nightingale amps reveal a slightly crisper strike and a deeper view into the tonality of decay, as hammers lift off the celesta’s metal bars.

Both of these amplifiers are well balanced within themselves; neither has overt strengths or weaknesses, and one amp's sonic attributes don't overshadow all others. Searching for an analogy, it is as if I hear the same performers or orchestra under different lighting. The C-J amp is incandescent to the Nightingale’s halogen. The ATS-90s have a lower noise floor, are faster-sounding and tonally more resolving; they reveal truer colors. And likewise with the lighting differences, the Premier 140 is warmer and sweeter, whereas the Nightingales are drier and more neutral -- in comparison their highs are slightly more extended and their lower midrange is leaner yet clearer and more focused. Keep in mind, however, that these are strictly relative comparisons. Each amp is capable of solid, punchy bass. Bass from the ATS-90s is better defined, both in terms of speed and tonal definition; bass from the Premier 140 has a wee bit more heft. The Nightingales’ splendid bass tonality really enhanced my appreciation of big symphonic works.

Nightingale amps playing Norah Jones’ "Nightingale" (Come Away with Me [Classic Records JP 5004]) bring her lips closer to the microphone -- at the intro her voice is mapped onto the same space as the guitar. Her voice is slightly more fragile, with the faintest lack of mid-lower-end weight as compared to the way it is with the Premier 140, where it is smoother, more homogenized. The ATS-90s reveal that her drummer is really at it fast and furious, though quietly. Microdynamics are superb -- you hear a lot of different licks. While all the drumming is still there with the C-J amp, it is not as prominent and not as clear. Each amp lays out the players well, but the ATS-90s draw tighter edges around the space between instruments, in turn better defining the performers within it.

Are the Nightingale ATS-90s, like the Conrad-Johnson Premier 140, deserving of the Reviewers' Choice appellation? That additional $5600 is the sticking point -- it pushes the ATS-90s into cost-no-object, super-amp territory. There's no question that both amps offer an equally valid sonic view, with differences in perspective. I own the Premier 140, so my vote is cast. But it is election season here in the US, and the ATS-90s are very persuasive.


Earlier I noted difficulty wrenching myself away from the music and back to considering the Nightingale ATS-90s as components -- I’d get out, and the amps pull me back in. My notes are peppered with comments such as "I could live with these" and "a music-lover's amplifier." The aesthetic has an easy-on-the-eyes, timeless character, and the ATS-90s' performance is wholly satisfying. To give you their best, they deserve to be surrounded by quality equipment.

Although the Nightingale brand is new in the US, if these amps fit your price range, you should put them on your short list. It is heartening to recognize there are music lovers throughout the world whose passion drives them to build components that bring truth to reproduction. To Signore del Rio, I say, "Bravo! Bravo!" The Emperor would be pleased.

...Tim Aucremann

Nightingale ATS-90 Mono Amplifiers
$12,595 USD per pair.
Warranty: Two years parts and labor (except vacuum tubes).

Simetel S.p.A.
Via Pieve Torina 42
00156 Rome, Italy
Phone: +39064121091
Fax: +39064110557

E-mail: welcome@nightingale.it
Website: www.nightingale.it/english/home.html

North American distributor:
O. S. Services, Inc.
10153 1/2 Riverside Drive, #159
Toluca Lake, CA 91602
Phone: (818) 632-0692

E-mail: randy@ossaudio.com
Website: www.ossaudio.com

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