Tube Power Amp Reviews

Not only was the Reference 75 capable of rendering dynamic swings on great recordings from pppp to ffff; I was also able to hear 10 to 15 dynamic intervals between pp and p. In short, the amplifier was able to reveal musically meaningful dynamic variation in recordings I'd previously thought sounded rather flat. Even soloist János Starker's performances in the cello concertos of Saint-Saáns (CD, Mercury Living Presence 432 010-2) and Dvorák (CD, Mercury 432-001-2), both with Antal Doráti conducting the London Symphony Orchestra, were presented with thundering dynamics, every attack of Starker's bow on his instrument kicking like a gunshot.

The ARC had superb detail resolution, especially in the critical midrange, which added a startling degree of realism to While You Are Alive, my favorite of the recordings by Cantus engineered by John Atkinson (CD, Cantus CTS-1208). The opening passage of Erik Whitacre's Lux Aurumque has several very-low-level passages in which the choir resolves on a major chord, and the ARC was able to delineate these masterful singers' precision of pitch. With "Prana," from Liam Sillery's Outskirts (CD, OA2 22050), it was very easy to follow the two melodic lines of Sillery's trumpet and Matt Blostein's alto saxophone. Three male choirs sing on Psalms of Consolation and Hope, with George Guest directing the Choir of St. John's College and John Scott on pipe organ (LP, Argo ZRG 892): one each of adult males, older boys, and younger boys. Through the ARC, each group was easy to distinguish on the wide, deep soundstage—the Ref 75 separated the men from the boys.

The amp's resolution of detail was such that I was frequently able to "see" into the performances of many recordings. In Derek Bailey's Improvisation (CD, Ampersand 2), the amp's unraveling of the guitarist's unique string attack and harmonic chiming was so clear and clean that I could almost visualize how he was executing these effects on his instrument. With Tom Chiu's performance of David Chesky's Violin Concerto, with Anthony Aibel conducting (SACD/CD (CD layer), Chesky SACD 288), I was able to follow each instrument of the Area 31 ensemble as it floated on a bed of air. I was virtually able to re-create the score in my head.

My most chilling experience was listening to Michael Riesman conduct the Philip Glass Ensemble in the final movements of Glass's Einstein on the Beach (CD, Nonesuch 79323-2). This is my favorite Glass work; I prefer this 1993 recording to the first recording, from 1978, and have seen three performances of the opera over the last 30 years. Although Riesman has so far conducted every performance and recording ever made of the work, I was floored by the level of musicianship he coaxed out of a 2012 performance in New York. I sat riveted throughout those five hours, but the highlight for me was the bus driver's narration in the final scene. The actor-singer's performance was so dynamic, riveting, and personal that it gave me chills. When I played the final passage from the Nonesuch recording through the Ref 75, l was stunned—not because the bus driver on the Nonesuch recording equaled that of the 2012 New York performance (he didn't), but because the Ref 75 gave such a realistic facsimile of the singer standing in my listening room that I was mentally and emotionally transported back to the Brooklyn Academy of Music. I relived my experience of that night, which remains the most moving classical performance I've witnessed in the last 20 years. When the recording ended, I began to cry.

The ARC's ability to render instrumental images holographically on a bed of air with extraordinary detail and ambience meant that I was frequently fooled into thinking a live musician was playing in my living room. I had that experience with János Starker's recording of J.S. Bach's Suites for Solo Cello (CD, Mercury Living Presence 432 756-2), as well as with the solo guitars on Mark Ribot's Silent Movies (CD, Pi PI34). What was even more remarkable with solo classical performers was that the ARC amp unraveled so much detail, delicacy, and transient accuracy that I was able to appreciate certain performers' technical virtuosity more than through other amps. I had this experience with Gina Bachauer's recordings of the Chopin piano concertos, with Antal Doráti and the London Symphony (CD, Mercury Living Presence 434 374-2), and with guitarist Pepe Romero's Flamenco! (CD, Mercury Living Presence 434 136-2).

The Ref 75's resolution of detail also let me more easily distinguish between greater and lesser recordings. Although I'm a huge fan of both John Coltrane's Stardust (CD, Prestige 7268) and Chick Corea's Early Days (CD, Laserlight 17082), and I know that the Coltrane is a spectacularly natural recording, the Ref 75 revealed that the gap in recording quality between these two was much greater than I'd realized, especially during Corea's piano solos. And unfortunately, with "Sex Kills," from Joni Mitchell's Turbulent Indigo (CD, Reprise 45786-2), my favorite recording from her late period, it was obvious just how much electronic manipulation and digital compression had been applied; in terms of sound quality, it was far less satisfying than any of Mitchell's recordings from the 1960s and '70s.

But the Ref 75's greatest strength was in the bass. If my past experience of tube amplifiers has inclined me toward a bias, it's this: I haven't been crazy about the bass performance of tube amps of less than 100Wpc, including the ones I've owned. I've found that lower-powered tube amps tend to lose definition and slam, particularly in the lower bass. Not so the Reference 75. In the midbass, acoustic instruments sounded clean and uncolored, with great articulation, speed, and definition. And in the bottom two octaves the ARC had so much slam and authority that it behaved more like a high-powered arc-welder of a solid-state amp. With jazz tracks such as "Chairman Mao," from Denny Zeitlin and Charlie Haden's Time Remembers One Time Once (CD, ECM 1239), and "Our Love Is Here to Stay," from Bill Evans's At Shelly's Manne-Hole, I could hear the strings resonating separately from the wood on the respective double basses of Haden and Chuck Israels. Listening to "Where Will I Be," from Emmylou Harris's Wrecking Ball (CD, Asylum Elektra 61854-2), I was able to follow Daniel Lanois's electric-bass line perfectly, even though it's deep in the mix.

Victor Wootten's bass-guitar solo in "Cosmic Hippo," from Béla Fleck's Flight of the Cosmic Hippo (CD, Warner Bros. 26562-2), was so dramatic, dynamic, and in-my-face that I scribbled in my notes "Bass My God!" I had a similar reaction to the bass-synth lines in "Hunter," from Björk's Homogenic (CD, Elektra 62061-2), and Chris Jones's "Midnight Sun" (LP, 45rpm single, Surface Tension STNS002). The Ref 75's bass capabilities were demonstrated most startlingly with "Artemisia Absinthium," from Absinthe, the final album by John Zorn's Naked City (CD, Avant 004). Here Zorn, Bill Frisell, Wayne Horvitz, Fred Frith, and Joey Baron forgo their usual axes to perform works in the ambient genre. I don't know what instruments they are playing on this track, but most of the sounds generated are in the 20–50Hz range. Through the Reference 75, while the music thundered and bellowed across the front of the soundstage and shook the room, it was still easy to hear the subtle percussion textures across the rear of the stage. By now my two shelties have heard just about everything in my listening room, but this tune bothered them a lot.

The recording that at last put the ARC Reference 75 together for me was of my favorite classical work, George Crumb's Music for a Summer Evening (Makrokosmos III), for two amplified pianos and two percussionists (LP, Nonesuch 71311). This 1976 recording, by pianists Gilbert Kalish and James Freeman and percussionists Raymond Des Roche and Richard Fitz, is, in my view, the definitive performance of this work, and I was fortunate to hear this group perform it at New York City's Symphony Space in 1979, followed by a question-and-answer session with Crumb. The piece is replete with ambience, decay, and huge dynamic swings that include very delicate textures and crashing percussion. (The pianos are amplified, Crumb explained, not to add distortion, but to give a single piano the dynamic range of an entire orchestra.) The recording is an acid test for how an audio component deals with transients, dynamics, detail, and ambience retrieval. I was so struck by how well the ARC created an involving reproduction of the work that I sat through its entire 40 minutes, which I hadn't done in 15 years. The dynamics were startling, and more forceful than I recall from the live performance (well, my seats weren't that good).

I mainly chose this recording to test the ARC's power capabilities. When my wife and kids are around, I play music at a lower level than when I'm alone—among my audiophile friends, I have a reputation for playing music at louder levels than most people like. I cranked up the volume to a level that was about the maximum I could stand, to hear how the Ref 75 would handle the two sections of the third movement, The Advent, which ends in simultaneously crashing pianos and full percussion blasts (footnote 1). The effect was startling, with no trace of strain, distortion, or compression. And the VU meters registered an output of only 25W.

Could that be? The loudest volume I could stand in my 10' by 35' by 11' (at its highest point) listening room was being created by only 25W? I decided to push the Ref 75 further. I put on "Walking on Sacred Ground," from Chad Kassem's remastering of Janis Ian's Breaking Silence (CD, Morgan Creek/Analogue Productions CAPP 027). (Time for reissues of this one, Chad, on LP and CD.) I turned it up louder than I could stand it. My ears started hurting and I ran out of the room. From two rooms away, I called my audiophile friend Dudley Smalls and told him I couldn't believe how loud the amp was playing. Dudley noted that the music sounded pretty clean and undistorted over the phone. He said he wondered how much power the amp was using. Holding my hands over my ears, I ran back into the room to check how far into clipping the meters were registering on the peaks—their scale far exceeds the Ref 75's claimed output of 75Wpc. "45W," they said.

Comparisons
I compared the Reference 75 with my Reference 110 ($9995 when last offered), which has the stock 6550C output tubes. (Although all current ARC power amplifiers are fitted with KT120 tubes, the company offers Ref 110 owners the choice of retubing with 6550Cs. Not all of ARC's 6550C-based power amps will accept KT120s, however.) I could easily hear microdynamic inflections through the Ref 110, which also had the same delicate midrange as the Ref 75. However, the 110 conveyed less inner detail and decay. Transients were also somewhat less articulate, with a slight bit of sibilant smear.

The Ref 75's bass definition was fairly close to the Ref 110's, but bass attacks were more articulate and bass pitches more easily followed through the 75. The Ref 75 also had a much wider dynamic range, with more subtle gradations of dynamics, as well as more "jump factor." And despite the fact that the KT120 has the reputation of being a more neutrally balanced tube than the 6550, the 110 had a slightly more forward sound than the Ref 75 with high-level passages.

It would have been interesting to do a three-way comparison—my Reference 110 with KT120 and 6550C tubes vs the Reference 75 with KT120s—to see how close the sounds of the 110 and 75 might come when driven by the same output tubes. However, as the 6550Cs in my Ref 110 aren't anywhere near the end of their useful life, I was reluctant to buy eight new KT120s just to satisfy my curiosity.

Conclusions
The Reference 75 touched me on a deeply personal level. I enjoyed listening to music so much through it that every time I entered the listening room and saw its silvery hulk beckoning to me, I turned it on and played some music. More than with any other component I've reviewed, when the Ref 75 was in my system, I went out of my way to make sure, every chance I could, that music was playing.

I expect the Reference 75 will create some marketing problems for Audio Research. It has no flaws, and several strengths that exceed the performance of any amplifier I've heard in my home. And if it's true that amplifiers with a single pair of push-pull output tubes have a certain "magic" that can be lost when multiple pairs of tubes are ganged to create great power output, then I wonder how the sound of some of the higher-powered ARC amps will stand up to the Ref 75. And while the speakers I used with the Ref 75 were fairly efficient, I did play them at very loud levels in a very large room, and not once did I tax the amp's power-delivery capabilities. I would suspect that unless someone has very insensitive loudspeakers and/or a very large room, it would be difficult to make a case for why anyone would need an amplifier with more power than the Reference 75.

I wrote what was to have been this review's final paragraph some time ago:

"John Atkinson has said that there is no greater praise a reviewer can give a component than to purchase it for use in his own reference system. And although I loved my time with the Reference 75, and felt it equaled or exceeded the performance of my Reference 110 overall, I still love my Ref 110. With the decline of the financial-services industry in the recent meltdown, I'm earning a fraction of what I did 10 years ago, even as I have one child beginning college this year and another not far behind. I can't justify the luxury of purchasing a new stereo amplifier this year."

The hell with it. I'm buying the Audio Research Reference 75.

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Footnote 1: I admit it: I stole this effect for the finale of "Mansour's Gift," from my jazz quartet Attention Screen's Live at Merkin Hall (CD, Stereophile STPH018-2). I'll bet that passage has the widest dynamic range of any of John Atkinson's Stereophile recordings.