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Pathos Acoustics Aurium Headphone Amplifier

May 2014

Pathos AuriumEstablished in 1994 in Vicenza, Italy, Pathos Acoustics has become widely known as an innovative manufacturer of fine audio electronics with stunning industrial designs that are as eye-catching as their sound is wondrous. Guided by a design philosophy that declares that each new product must have a technical advantage over similar gear in its category, as well as an arresting look that announces it as something unique, every Pathos model exudes postmodern Italian sophistication.

When I visited Pathos for SoundStage! Hi-Fi in September 2007, I saw this rigorous standard applied to each product made, and came away impressed with the company and the leadership of its founders: research-and-development director Giovanni Borinato; Gaetano Zanini, who fine-tunes the products and is responsible for production; and industrial designer Paolo Andriolo. It was a treat to witness Pathos’s meticulous manufacturing processes: the exposed inner complexity of the Endorphin CD player (like a pod of Abu-Dhabi condos), heatsinks being cut and polished, a case being machined for the gorgeous InPol2 amplifier.

So when SoundStage! Network publisher Doug Schneider asked, soon after the 2013 Rocky Mountain Audio Fest, if I’d be interested in reviewing the new Aurium headphone amplifier ($1495 USD), I jumped at the chance, not only already confident in the quality of the product but also intrigued that, after 20 years in mainstream audio, Pathos was now expanding into head-fi. I expected to be delightfully surprised.

Design

According to Enrico Fiore, director of marketing, the idea of the Aurium came from Pathos’s desire to develop its share of the fast-growing market of personal audio among younger listeners by contributing its unique technology of Insequitore a Pompa Lineare (InPol) -- in English, Linear Pump Tracking.

From the start, the Pathos engineering team, led by Roberto Gianotti, conceived of the Aurium as a hybrid design -- as have been all Pathos electronics since their very first amp of 20 years ago, the Twin Towers integrated. The Aurium has tubes and a MOSFET output stage, wedding the natural harmonic wealth of valves to the energy and control of solid-state. In this InPol circuit, the two Electro-Harmonix 6922 tubes don’t merely serve as a preamp, but act as both preamp and power-output tubes. The MOSFET output then acts as a tracker with unity gain for, in theory, a cleaner signal. Pathos takes pains to ensure a shorter signal path and reduces the parts count by omitting any unnecessary components that might contaminate the signal.

Pathos faced some intriguing challenges in designing the Aurium. To enable its relatively high output power, a robust and accurate switching power supply had to be designed and built. Also, an auto-bias system needed to be incorporated in order to prevent thermal drift of the MOSFETs. Then, for efficient cooling, Pathos had to carefully leverage the excellent cooling properties of the Aurium’s fully CNC-machined aluminum case. And to present a clean front panel in keeping with the Pathos aesthetic, the Gain/Impedance and Balance controls are on the rear panel. Finally, the Aurium’s two EH6922 tubes rise from the Aurium’s top panel, each semi-protected by three radial fins of metal, to give the Aurium the overall “nude” look that is so much a part of Pathos design: key elements of inner electronics used as important aspects of outward appearance.

Despite its relative economy of circuit, the Aurium has a long list of technical features: class-A, zero-feedback operation; a special volume control; multiple connections, balanced and single-ended; a claimed frequency response of 10Hz-80kHz; a low total harmonic distortion of 0.1%; and a relatively high output power of 3.6W into 16 ohms to ensure that the Aurium can drive a wide selection of headphones. Pathos feels that class-A is the “main road” to great amplification: it minimizes crossover distortion and renders unnecessary any negative feedback, which can compromise linearity. And instead of putting the controls (volume, gain/impedance, balance, input selector, etc.) one behind the other along the signal path, which can degrade the signal, Pathos uses a microprocessor to control all volume functions, resulting in a much shorter signal path.

Description and setup

The Aurium came from Audio Plus Services, Pathos Acoustics’ North American distributor, wrapped in a plastic bag and nested in foam cutouts in a medium-size cardboard box. Included were a 12V power-supply wall wart with umbilical, a user’s manual, and two pages of operating instructions.

The Aurium is a squarish, compact box measuring 7.8”W x 2.3”H x 9”D and weighing 6.6 pounds. Its case is made of fine-grained aluminum available in silver-gray or black, the top plate perforated on each side with three parallel rows of ventilation holes; toward the rear, the two EH6922 tubes rise from the top plate just over an inch. On the bottom plate are four feet of noncompliant plastic. The warranties are 30 days for the tubes, three years for parts and labor.

On the faceplate, from left to right, are two pushbuttons, for On/Off and input selection, between them an On/Off LED; above these are four vertical slot LEDs to indicate the input selected. To the right is a large volume knob of studded aluminum, and in the bottom-right corner is a 1/4”, single-ended stereo headphone jack.

Pathos Aurium

On the rear panel are, from left to right: two small 12V jacks (one each for the power supply and a remote on/off output, to be added later), knobs for Balance and Gain/Impedance, pairs of balanced (XLR) and single-ended (RCA) outputs, three sets of single-ended inputs (RCA), the serial-number badge, and a pair of balanced (XLR) inputs. This wealth of connections, which permits listening via headphones and speakers without the user having to swap interconnects, makes it possible for the Aurium to function as the center of a complete and flexible audio system. But I used it only as a headphone amp.

Setup was easy-peasy. I plugged the wall wart into my power distributor, connected the wart’s umbilical to the port on the Aurium’s rear, ran a pair of RCA interconnects from my Resonessence Concero HD DAC (connected in turn to my iMac via USB) to one of the Aurium’s inputs, and inserted the single-ended plug of a set of headphones into the jack on the faceplate. My iMac runs OS Mavericks v.10.9.1 and JRiver Media Center 19.0.55. I listened to the Aurium through three sets of headphones: my Sennheiser HD 650s, a pair of Ultrasone Edition 8s (graciously loaned by Dan Muzquiz of Blackbird Audio), and Audeze LCD-3s (in for review).

I had to adjust the Aurium’s Gain/Impedance knob for each set of headphones I used. It’s a 6dB attenuator, and I found it very useful. For the Ultrasone Edition 8s, the most sensitive of the three, I had to turn the gain down. For the Sennheiser and Audeze ’phones, both of which are relatively insensitive, I had to turn it up -- and for the Audezes, all the way up. However, I rarely needed to turn the Volume knob on the front panel past 1 o’clock. That was usually plenty loud for even the most magisterial orchestral work or any acid rock.

One note: The first review sample I received had some problems with its Balance control: No matter where I set the knob, the right channel was always much louder. Still, at the urging of Audio Plus Services, I worked with it for nearly a month before finally insisting that the control was faulty. I was immediately sent a replacement, which operated without problems for the remaining two months of the listening period.

Listening with different headphones

Of the three sets of headphones I used with the Pathos Aurium, the closed-back Ultrasone Edition 8s proved easiest to drive. Their claimed frequency response is 6Hz-42kHz (no tolerance given), with a nominal impedance of 30 ohms and a sensitivity of 96dB. The Edition 8s produced detailed, resolved sound that created the pleasingly convincing illusion of a soundstage. It wasn’t terribly wide or deep, but it also wasn’t placed somewhere between my ears, as with the other two sets of ’phones. Besides the Ultrasones’ terrific resolution, bass was their forte, which made jazz and rock particularly exciting. I loved hearing Jack Bruce’s thundering bass line in “Sunshine of Your Love” from Strange Brew: The Very Best of Cream (16-bit/44.1kHz ALAC, Polydor), for example, or Orlando Cachaito Lopez’s deeply resonant double bass in “Tumbao No.5 (Para Charlie Mingus)” from Cachaito (16/44.1 ALAC, Nonesuch). This performance on nearly unaccompanied bass features a repeated figure with ornaments and variations, and some fast walking and double-stopping, full of impact and thrilling glissandi. Through the Aurium, the Edition 8s sounded, overall, lighter than the other two ’phones.

My open-backed Sennheiser HD 650s have a claimed frequency response of 10Hz-39.5kHz, -10dB, an impedance of 300 ohms, and a rather high sensitivity of 103dB -- they’re generally considered a bit hard to drive, but the Aurium had no trouble. The Sennheisers weren’t quite as resolving as the Ultrasones, but were somewhat airier in the highs and richer in the midrange. They handled all genres of music very capably, though without the Edition 8s’ tight, prodigious bass. And though lighter in impact than the Ultrasones, the Sennheisers presented orchestral music more even-handedly, reproducing the lushness of violins as well as their bite. I particularly loved horns and brass through them -- the fanfares in the second movement of Sibelius’s Symphony No.2, performed by the Minnesota Symphony under Osmo Vänskä (24/96 FLAC, BIS), were tastefully brash and sudden. But HD 650s also excelled with guitars and voices. Besides her contralto, Linda Ronstadt’s cover of Warren Zevon’s “Carmelita,” from her Simple Dreams (16/44.1 ALAC, Asylum), also features two acoustic rhythm guitars strummed in a march-like, Mexican style, and a solo on pedal steel guitar that sounded alternately silky and then organ-like. Through the HD 650s and Aurium, this track unrolled a superb tapestry of varied timbres.

Pathos Aurium

Perhaps most impressive was how the Aurium was able to drive the Audeze LCD-3s -- open-backed planar headphones that can sound veiled and bass-heavy with lower-powered amplification. With a listed sensitivity of 91dB at 1mW, the LCD-3s are pretty hard to drive -- Audeze lists their optimal power requirement as 1-4W. The Aurium’s generous 3.6W lit them up so well that I found the LCD-3s close enough in resolution to the HD 650s, and superior in richness, bass, and overall slam and impact. The Audezes’ claimed frequency response is prodigious -- 5Hz-50kHz -- and their nominal impedance is 45 ohms, purely resistive. The rest of the listening observations in this section all refer to what I heard with the Pathos Aurium driving the Audeze LCD-3s.

Consistently, the Aurium’s sound was harmonically rich, resolving, and robust in terms of power, punch, and slam. Dynamic scaling and contrasts were always convincing, and with every kind of music. The Aurium reproduced with great timbral acuity the rich textures of violins, woodwinds, pianos, and horns, and with a spectral balance that didn’t favor or spotlight any one sector of the audioband. It never sounded pushed or strained, tipped up or bass heavy. My listening experience was entirely delightful.

From the start, however, I wanted to know how the Aurium would handle orchestral strings, particularly violins. In my experience, the violin is the instrument most difficult to reproduce by any electronics, loudspeakers, or headphones. Violins can sound thin, wiry, whiny, or like a chorus of water faucets piping away. Live, orchestral violins sound rich, highly articulate, and somewhat varied in tonal palette: sometimes lush in the midrange, sometimes with a biting attack but sweet trebles. They sound not like glary nothings of etched glass, but like what they are: strings, ebony, and finely lacquered wood.

In the first movement of Julia Fischer’s recording of Tchaikovsky’s Violin Concerto, with the Russian National Orchestra conducted by Yakov Kreizberg (24/96 FLAC, Pentatone), the soloist’s beautiful string tone was reproduced by the Aurium and Audezes as sounding supple and sweet, with a sharp bite when called for. Her violin sounded truly silky, sometimes with a sustained vibrato reminiscent of Heifetz. The orchestral violins were lush, with deft touches. In Mozart’s Serenade No.3 in D, K.185, with Bruno Weil leading Tafelmusik (16/44.1 ALAC, Sony Classical), I heard fine string tone and textures even from this “Red Book” file. The violins in the first movement sounded sprightly and speedy, but with appropriate weight in the midrange and in the forte passages, when the cellos enter. All was quick, with a fine top end entirely without glare, glassiness, or distortion.

Horns, acoustic guitar, and woodwinds also fared very well. “One for Tom,” from Paquito d’Rivera’s live recording Brazilian Dreams (16/44.1 ALAC, MCG Jazz), features a varied horn section that will test the expressive palette of any playback system. The Aurium was up to the task, beautifully rendering D’Rivera’s alto sax and distinctive vibrato, and Claudio Roditi’s powerful trumpet, in their successive solos and in the following duet. When Jay Ashby’s trombone entered, I felt the bell and the plosive impacts of his attacks inside it. D’Rivera’s clarinet sounded rich and clear in the midrange notes, speedy and lightly piercing (in a good way) in the highs.

I don’t think I could have asked for better piano sound. With lesser gear, notes occasionally sound blurred -- and sometimes etched, as if carved from marble rather than gently beaten gold. The Aurium consistently captured the piano’s full expressiveness in works by Franz Joseph Haydn. In the Sonata No.53 in E Minor, H 16 No.34, performed by Alfred Brendel (16/44.1 ALAC, Philips), the emphatic trills, delicate and sprightly, and complex, rondo-like passages demonstrated all of the work’s subtly assembled drama. I heard a great weight to the lower end of the keyboard in the Allegro moderato of Haydn’s Piano Concerto in G Major, H 18 No.4, played and conducted by Leif Ove Andsnes with the Norwegian Chamber Orchestra (16/44.1 ALAC, EMI). Also captured were great dynamic and timbral contrasts between high and midrange notes in the interaction between Andsnes’s arpeggios and the answering accompaniment from violins.

What about rock’n’roll? The Aurium delivered there, too. “One,” from U2’s Achtung Baby (24/44.1 FLAC, Island), begins with eloquent strumming from two lightly amplified electric guitars, one sounding almost acoustic, then gives way to the Edge’s ringing lead guitar on a repeated figure. Bono’s screaming vocal, increasingly operatic as he climbs to his higher register, seemed to fade into the Edge’s chiming guitar as it trailed away to the end with a light distortion. In the intro to “Money for Nothing,” from Dire Straits’ Brothers in Arms (MP3, Warner Bros./Amazon Cloud), Mark Knopfler’s electric guitar sounded crisp, tight, and snarling, with satisfying, controlled distortion. But perhaps best was the booming riff played by Jack Bruce on his Gibson EB-3 bass, doubled by Eric Clapton’s fuzz-boxed Gibson SG, in Cream’s “Sunshine of Your Love.”

Pathos Aurium

Voices were great, no matter the genre or gender. In “The Weight,” from the Band’s Music from Big Pink (16/44.1 ALAC, Capitol), Levon Helm’s gritty Arkansas tenor came through with all its pain and gospel inflections. Accompanied by Rick Danko’s high-pitched wails and Richard Manuel’s falsetto in the choruses, Helm’s dramatic singing, so full of character, contrasted beautifully with the others’ plaintive voices. Bonnie Raitt’s familiar contralto sounded airy, strong, and bluesy in “Right Down the Line,” from Slipstream (MP3, Redwing/Amazon Cloud). The Huelgas Ensemble, a large choir, sounded airy and spacious, with deep bass and a reverberant hall sound, in “Introitus,” from Jean Richafort’s Requiem, led by Paul van Nevel(16/44.1 ALAC, Harmonia Mundi). The voices of the tenors and sopranos soared like a cloud slowly billowing taller, with clear, pure tonalities in a rich harmonic tapestry. It was gorgeous.

Power and orchestral scaling were a big plus with the Aurium, its 3.6W output helping it sail through difficult passages or entire recordings with ease. The sequence of arias from Verdi’s La Traviata beginning with “Lunge da lei . . . ,” as sung by Rolando Villazón on his Italian Opera Arias (16/44.1 ALAC, Virgin Classics), is one of the most amp-clipping pieces I know of. This music is particularly showy and dramatic; Villazón’s tone is dark and somber when he begins, but quickly ramps to powerful, shimmering highs and, at the end, a fast vibrato. The Aurium had no trouble rendering it all radiantly. The beginning of the second movement of Sibelius’s Symphony No.2 has rolling timpani, comically piping woodwinds, and ominous, sweeping strings. The Aurium was comfortable reproducing both the weight of the orchestra and this delicious variety of timbres. About midway through, a stark oboe solo gives way to lightly bowed violins playing the theme, which then turns urgent, the violins playing increasingly loudly, surrounded by punchy horn fanfares. Each of these passages -- full of dynamic contrasts, dramatic tensions, spatial layering, and lovely orchestral weight and depth -- was handled easily and nimbly by the Pathos Aurium.

Comparison

At about one-third the price ($480) and less than half the size of the Pathos Aurium, my Heed CanAmp’s all-solid-state circuitry may be nearly as effective as the Aurium’s hybrid one. Outfitted with an internal power transformer (no wall wart), the Heed uses an op-amp in its first gain stage and a single-ended, class-A output stage. It’s a very decent headphone amp blessed with what seems a like amount of power (alas, no specs available to confirm this). It drove all three headphones handily, but sounded most balanced with the Sennheiser HD 650s. And compact as it is, the CanAmp fits even more nicely into my desktop system. But other than a volume knob, it has no controls, and only one set each of inputs and outputs, both single-ended. It generally does very well with all types of music, creating a satisfying, often tonally saturated sound full of snap and presence, but lacks the refinement and openness of the Pathos Aurium.

Paired with the Audeze LCD-3 ’phones, the T+A DAC 8 ($3250) came much closer to the Pathos Aurium’s sound. The DAC 8 includes an excellent headphone amp, but of course it’s also a fine PCM DAC -- I can’t make an apples-with-apples comparison of it and the Pathos Aurium, which depended on the Resonessence Concero HD for a signal. Still, I found the contrast useful.

Though the T+A DAC 8 couldn’t match the Aurium for pure power, its sound at near maximum volume was comparable in quality. While the Aurium was definitely better through the midrange -- richer, fuller, weightier -- the DAC 8 sometimes had better, tighter bass. In Fauré’s Requiem, with Ed Spanjaard conducting the Netherlands Chamber Choir and the Maastricht Symphony Orchestra (24/96 FLAC, Pentatone), both organ and orchestra had more weight and presence. There was slightly more quickness with the DAC 8, and the choir sounded airier, more open and clear, with somewhat better dynamic contrasts, all of which created a greater illusion of depth. The organ’s pedal notes were also better defined than with the Aurium and Concero HD DAC.

But with most music, the DAC 8 sounded consistently thinner, drier, and less dimensional. In the series of Verdi arias, Rolando Villazón’s tone was perceptibly harder, his ping more pronounced. In “The Weight,” Levon Helm’s voice fell back a bit in the mix, and all of the Band’s voices sounded thinner. The combo of Aurium and Concero HD usually sounded sweeter, purer, and a bit more forward with voices. It was the same with Paquito D’Rivera’s clarinet and alto sax, with the Sibelius symphony, and Richafort’s Requiem. The Aurium-Concero HD combo was consistently a touch sweeter, harmonically richer, and tonally more saturated, with smoother transients -- and generally more pleasing.

Pathos Aurium with T+A DAC 8 and Sennheiser HD 650

At the very end of the listening period, I switched back to my Sennheiser HD 650 headphones, hooked up the Pathos Aurium to the DAC 8’s analog outputs, and got astonishing, thundering, highly detailed sound in the first movement of Brahms’s Piano Concerto No.2, as performed by Hélène Grimaud with Andris Nelsons leading the Vienna Philharmonic (24/96 FLAC, Deutsche Grammophon). There were stupendous inner details in sustained, individual notes from her piano, and the lower registers had a wealth of harmonics I hadn’t heard before. String tone was to die for, and inner details were such that I thought I could hear the speed of the string vibrations -- the sound was that clear. Orchestral tutti had prodigious force, and the dynamic contrasts in both the solo-piano and orchestral passages kept unfolding more of the Aurium’s resources in terms of resolution, precision, and power. Nor was there any lack of sweetness or richness. This combo had it all. But when I tried balanced operation, via the DAC 8’s XLR outputs and the Aurium’s XLR inputs, the sound was a click or two louder and a touch less mellow than single-ended.

Conclusion

The Pathos Acoustics Aurium headphone amplifier integrated perfectly with my home head-fi system, fitting neatly in a corner of my desktop between my iMac and five-shelf audio rack. It performed capably with three different headphones, each with a different sonic signature and power needs. Aside from the first sample’s faulty Balance control, I encountered no problems with its operation. I adored its looks. And I loved its sound, which served every kind of music equally well.

Pathos Aurium

Today, the crowded category of headphone amplifier offers many good options, whether all-tube, all-transistor, or hybrid. If you’re looking for something with real power and versatility, arresting looks, and seriously good sound, I heartily recommend the Pathos Acoustics Aurium. You may end up buying one. I did.

. . . Garrett Hongo
garretth@soundstagenetwork.com

Associated Equipment

  • Digital sources -- Apple iMac computer running Mavericks OS 10.9.1 with JRiver Media Center v.19.0.55; T+A DAC 8 and Resonessence Concero HD digital-to-analog converters.
  • Headphones -- Audeze LCD-3, Sennheiser HD 650, Ultrasone Edition 8
  • Headphone amplifier -- Heed CanAmp
  • RCA interconnects -- Van den Hul The Orchid
  • XLR interconnects -- Audience Au24 SE
  • USB cables -- Wireworld Platinum Starlight 7 and Silver Starlight 7
  • Power cords -- Siltech Ruby Hill II and SPX-800
  • Power conditioner -- PranaWire Linebacker
  • Power distributor -- Siltech Octopus 8
  • Accessories -- edenSound FatBoy damper, Apple Mac Mini remote

Pathos Acoustics Aurium Headphone Amplifier
Price: $1495 USD.
Warranties: 30 days, tubes; three years parts and labor.

Pathos Acoustics SRL
Via Palù, Grumolo delle abbadesse
36040 Vicenza
Italy
Phone: +39 0444-264732
Fax: +39 0444-381275

E-mail: info@pathosacoustics.com
Website: www.pathosacoustics.com

US distributor:
Audio Plus Services
156 Lawrence Paquette Industrial Drive
Champlain, NY 12919
Phone: (800) 663-9352, (450) 585-0098
Fax: (866) 656-0686

E-mail: djacques@audioplusservices.com
Website: www.audioplusservices.com