April 15, 2009

deHavilland Fisher Model 50A Mono Amplifiers


Progress, by definition, is forward motion, even in audio. Glances back to accomplishments of the past are fine for enthusiasts of vintage gear and do-it-yourselfers, but established commercial outfits such as deHavilland Electric Amplifier Company aren’t supposed to take us back to yesteryear. They’re supposed to gallop us into a better-engineered future. At least, that’s what most high-enders would assume. But Kara E. Chaffee, chief engineer of deHavilland and for ten years known for the manufacture of superb, low-powered, single-ended-triode (SET) tube amplifiers, recently had an epiphany about a vintage, push-pull set of class-A monoblocks.

About 18 months ago, a reviewer friend (not I) asked Chaffee to restore to operating condition a pair of original Fisher 50A mono amplifiers, a model developed in 1954. She took them apart and, after getting completely familiar with their schematics and design, put them back together, this time with a bit more capacitance in the power supply. She came to see that the design was not precisely vintage, if vintage meant an overripe midrange, high coloration, and woolly bass. The 50A’s stock features -- dual tube rectification, choke-input power supply, interstage transformer drive, tube-regulated bias supply, and 1614 pentode tubes operating in triode output mode -- all shouted quality and translated into excellent sound by today’s standards. "The Fisher 50As were transparent yet full sounding," Chaffee told me recently in a phone conversation -- not thin, they produced excellent detail without being forward.

But after shipping the 50As off to her friend, Chaffee couldn’t get the sound of them out of her head. She sat down at her drafting board (she still uses a physical drafting board and mechanical pencils), began to draw parts, schematics, and values, and soon got the idea that she could manufacture this amp herself -- upgrade its parts, clean up its looks, and recapture its sound for the contemporary audiophile. To do this, she uses better grades of materials -- a milled aluminum chassis, a machined top plate and transformer endcaps -- and has beefed up the circuit with more current (four times as much in some places) and made some modifications. For sonic reasons, she replaced the original 12AU7 tube in the second gain stage with a 6CG7. She used a Lundahl interstage transformer to produce better bandwidth than the original, and put new old stock (NOS) Russian and Jensen paper-and-oil capacitors in the signal path instead of the paper-only caps Fisher had used. She eliminated one gain stage and an input-gain potentiometer, thus simplifying the amp’s front end and further increasing its transparency. Finally, she replaced the original 1614 output tubes ("which no one loved," she said) with reissue Genelex Gold Lion KT88s, which would operate in class-A and in triode mode -- just like the originals.

The result was one pair of deHavilland Fisher 50A prototypes, rated minimally at 40Wpc in push-pull. They successfully debuted at the 2008 Vacuum Tube State of the Art Conference in Vancouver, Washington. Chaffee also showed them at the 2008 Rocky Mountain Audio Fest, to acclaim from attendees and the audio press alike.

Description and operation

The deHavilland Fisher 50A monoblock ($7250 USD per pair) is smallish (9.25"H x 9"W x 16"D) and weighs about 42 pounds. A pair fit comfortably side by side in a conventional audio rack with usable space of about 20" wide or so. Each can also go next to the speaker it drives, in a more conventional monoblock placement. Very handsome, the 50A is available in natural aluminum, or with anodized black sides and a natural silver top plate. Each amp’s two transformer covers are black, with oblong ventilation slots on the rear surface, near the top. Though fairly retro in appearance, the 50A’s lines are clean, with little touches -- the Model 50A badge on the long side panel, the deHavilland logo in red on the narrow front panel -- that lend an air of contemporary suavity.

Each 50A has nine tubes: two KT88 output tubes (6550, KT90, and 6L6 tubes are drop-in replacements), one 12AU7 for the first gain stage, two 6CG7s (one for the second gain stage, one for voltage regulation), two 6CL6s for the interstage current drive, and two 6CK3 rectification tubes. Aside from the aforementioned Genelex KT88s, which are of new manufacture, Chaffee gets her results by using a mixture of NOS signal and rectifier tubes -- Sylvania, Amperex, RCA. The Fisher 50A operates in class-A, push-pull, triode mode. How much in class A? Chaffee says for more than 50% of its stated output -- to about 25W.

One retro feature that Chaffee retains as stock is the barrier strip on the rear panel, with its 4- and 8-ohm taps, but she also offers the option of Cardas binding posts with either the 4- or 8-ohm tap hooked up, depending on customer preference. With the Cardas posts, the ohm values of the taps can easily be converted, if any change is needed, with a simple solder job of one wire at the back of the chassis interior. My review pair had the Cardas binding posts set for the 8-ohm taps.

Also on the rear are the input for a 15A IEC power cord, a screw-in holder for a 5A fuse, and a ground-float switch. This switch, a feature on all deHavilland amps, is used mainly to shunt the ground so that it flows only through the RCA interconnects, eliminating potential ground-loop problems. It can be used or not, depending on individual circumstances, but there can be an audible advantage in floating the power-line grounds. I did so, using my interconnects for both my signal and ground-path return. Finally, as the amp’s input is exclusively single-ended, it has only an RCA input jack.

On the top of the 50A, near the front, is a simple on-off switch. Sitting between the two transformer covers, about midway and to the left side, is an onboard meter and switch for setting the bias of the output tubes. The top plate is perforated with two separate fields of air holes for ventilation -- one, measuring 3"x 3", near the 6CK3 rectifier tubes at the front end, and another, measuring 2" x 3", to the right of the bias meter. There is also a line of small holes between the transformer covers along the top left side of the amp. It all adds up to a look of functionality dressed with taste.

To bias the 50A, you simply fire it up and, after letting the rectifier tubes warm up for 20 seconds, flip and hold the bias-meter switch. This activates the meter, which reads the output current passing through the KT88s. Chaffee sets the bias at 140mA, which is marked by a bold red line on the scrolled meter face. The bias can be adjusted perfectly with a black knob next to the meter.

During the review period, most of which fell during the Oregon winter, I appreciated the moderate doses of heat with which the 50As cheerily warmed my study. But as winter turned to spring and outside temperatures rose above the low 70s, these class-A amps raised the temperature enough that I had to open a couple of windows to cool the room.

The deHavilland Fisher 50As sounded best after about 30 minutes of warmup.


The Fisher 50A amplifiers went into my reference system: Cary 303/300 CD player; Nottingham Spacedeck turntable with Heavy Kit, Nottingham 9" Spacearm tonearm, Zyx Airy 3 moving-coil cartridge (0.24mV), and Herron VTPH-2 phono stage; Thor TA-1000 Mk.II and deHavilland Mercury 3 preamplifiers; Air Tight ATM-2 stereo power amplifier; Von Schweikert Audio VR5 HSE loudspeakers (91dB/6 ohm); Cardas Golden Reference and Verbatim interconnects (RCA); and Verbatim speaker cables with jumpers.

Mainly, I listened to the Fishers using the deHavilland Mercury 3 preamp, and to the Air Tight ATM-2 with the Thor TA-1000 Mk.II or Mercury preamp. I use a Balanced Power Technology Clean Power Center passive line conditioner for the phono stage and preamp. The Cary player goes straight into the wall with a Harmonix XDC Studio Master power cord. The Fishers were each plugged into a Cryo-Parts power strip with Cardas Golden Reference power cables, and the strip itself was plugged into the wall with another Golden Reference. Other power cords were Thor Red, Fusion Audio Impulse, and Fusion Audio Predator. I have two 15A dedicated lines, both with Oyaide R1 duplexes. I used PS Audio Critical Link fuses in the Cary player and deHavilland preamp.

My equipment rack is a Finite Elemente Signature Pagode with Cerapucs under the Cary player. The room is treated with sound panels from Acoustic Sciences Corporation; bookshelves line the right wall, shelves of LPs the left. The listening room, which is also my study, is fairly small (12’ x 15’ x 8.5’); I listen both in the nearfield, and on a couch about 8’ away from the plane described by the front baffles of my speakers. The Von Schweikert VR5s are toed in about 3", so that the tweeter axes fire slightly to the outside of my ears in my standard listening position.

Vintage design, contemporary sound

Transparency wasn’t the first thing I thought of when I heard the Fisher 50As. Instead, I thought of tonal density and weight. The 50As created an audio tapestry -- an overall lavishness and permeable luxuriance open at times to stunning accents and sparkle, anchored by the gorgeous weight of its own fabric. Yet nothing seemed out of balance or over-the-top -- no artificial "detail" bordering on brashness, no thickened and overemphasized midrange masking a missing top end or bass, no too-forward treble or bass heaviness at all. These characteristics were akin to the signature deHavilland sound I’d come to know from the Aries 845 and GM-70 monoblocks. Their designer describes the 50As as "easy-goin’ and relaxed," but to me they sounded more refined and distinctive than that -- like a clear incoming tide that rushes over a reef, flooding the shallows with swirls and eddies of sound, surging and withdrawing seductively, then returning with an onrush of surf that curls through the clarity of the lagoon. I’d call their sound "romantic" except for their precision, the wealth of detail they provided, their fulsome sonic palette. The Fisher 50As could capture the weight of symphonic music, as well as all the snap and sizzle of a salsa band.

I began my listening simply, testing tone with a solo instrument that’s a particular favorite -- the cello, the baritone of the orchestral strings. János Starker’s recording of J.S. Bach’s Suites for Solo Cello (SACD/CD, Mercury Living Presence 470 644-2) sounded flat glorious. Starker’s cello could sound nimble and sprightly in the Courante from Suite 4, for example, a dance-like movement spiced with luscious octaves and rich in overtones. Or, in the Allemande from Suite 2, it could be dark, mordant, and brooding, with a sinuous and aching melodic line. Whatever the case, the character, pitch, resonance, and speed of vibration of each string was movingly evident and palpable through the Fisher 50As. As Starker’s quick intakes of breath punctuated these performances, the sublime illusion was presented of a single musician playing a single cello in my study, sonorously and tragically alive.

Next, I listened to a violin soloist with orchestra -- a recording of Henryk Szeryng performing Mozart’s Violin Concertos No.3 in G, K.216, and No.5 in A, K.219, with Alexander Gibson conducting the New Philharmonia Orchestra (LP, Philips Festivo 6570 024). Szeryng’s tone was just slightly dry, eschewing the silvery sound of Jascha Heifetz, but his expressive range seemed the greater for it, luxuriating in a darker, more somber mood in the Adagio of Concerto 3, before breaking through to an utter sweetness in the middle passages of his cadenza. In my experience, the sound of the violin is one of the hardest to reproduce -- many audio systems render it as all too glossy, impenetrable in its silkiness, creating spurious homogeneities of tone that belie the wide palette of timbres and musical emotions the instrument can convey. The Fisher 50As, though, made Szeryng’s violin even more expressive than I was used to, ranging through Concerto 3’s festive opening Allegro, the alternately dark and mellow Adagio, and finally to the sprightliness of the Rondeau (Allegro), revealing richer and more nuanced timbres, more complex harmonics, and a more saturated tone when called for. The orchestra piped, plucked, and bowed through a decorous, dancelike accompaniment that also demonstrated the vibrancy and grace of the Fisher amps.

On Ellington Indigos, Duke Ellington and his Orchestra play like a jazz chamber orchestra (LP, Columbia CS 8053). The first number, "In My Solitude," has a resonant and liquid piano intro by Ellington that gives way to comping as the horn section swings into the tune. Via the Fishers, the tune was sweet and warbling, with fabulous tonal weight and authority throughout.

And so it was throughout the entire LP: full, saturated saxophones; a brilliant and brassy trumpet; fabulously rich and weighty horn choruses; and bass thump and drive. Each solo instrument -- Russell Procope’s clarinet, Johnny Hodges’ alto sax, Paul Gonsalves’s tenor, Clark Terry’s trumpet -- had a gorgeous specificity, a tonal signature and boundaries that seemed like anchors of sound in the floating choruses of brass and woodwinds. Each cut was its own magical reverie -- sashaying saxes and brushes lapping a snare drum, metallic clouds of brass fanfares, a tinkle or stride from Ellington’s keys, and airy flights of solos floating in from anywhere in the orchestra. Listening rapturously, I couldn’t have been more happy than if I were sitting in a club as these gargantuan ghosts of jazz preached the silly out of me. The Fisher 50As and Ellington’s music were a perfect match -- both were rich in mood and complex in scope, harboring deep sonic momentum, then releasing it in the choicest drifts of airy nothing and such sweet thunder.

Talk about tonal weight and density -- Joe Cocker’s 1969 debut album, With a Little Help from My Friends (LP, A&M SP 4182), with its cast of superstar British sidemen, rocked me all over again. Tony Visconti’s ace engineering produced a dense, saturated tone, and the system captured it with terrific torque and resolution. Cocker’s smoky baritone, nowadays whittled down to a wheeze and a rasp, in 1969 had drive like a freight train, and his gospel skills were unmatched until Teddy Pendergrass came along. Hoots, swoops, sustained shouts, warbles -- Cocker had them all. "Sandpaper Cadillac," a little rock ditty probably thrown together in the studio by Cocker and keyboardist Chris Stainton, is a small showcase of these skills, along with the virtuoso accompaniment on electric guitar of Jimmy Page, formerly of the Yardbirds and on his way to Led Zeppelin. Stainton fills in on bass, piano, and organ as the other two sidemen lay down a funky blues walk of a start, piano and bass on the beat, while Cocker croons a bit before the shouts and hollers come, interrupted only by the tiny canticle of a solo-piano bridge. The Fisher 50As had no trouble controlling the VR5 HSEs’ dual 7" woofers; the tune’s bass foundation was always solid, without lagging or bloat. Page’s fuzz-box guitar obbligatos sounded punchy and crunchy, his tube-amp distortions (a Marshall with 5881s and GZ34 rectifier?) in time with the flow of the tune. And Cocker’s vocal snuck and snaked up to the climax of his signature sustained wail. There was that unmistakable grain to his voice, like a wisp of peat at the bottom of a glass of Scotch, the system capturing all its various shades of tone and shifts of vocal timbre all through the workingman’s waltz and whorehouse cha-cha of the song. What the Fishers did was render the tiny, blues-based accelerations and decelerations of the music’s momentum, and capture all the Cockney nuance of this Britband performance. In each passage, the sounds came through with shoulder-shaking immediacy, the music calling out to make my poor, beer-chugging, fiftysomething, Friday-night body move.

For contrast to this vintage rock, I put on some acoustic piano music. This was something the Fisher 50As excelled at, producing a vibrant, deeply resonant, harmonically rich sound no matter the format. From "Red Book" CDs, for example, I enjoyed pianist Ivan Moravec performing Chopin nocturnes, Alfred Brendel in Beethoven’s concertos, Emil Gilels playing Brahms’s Concertos 1 and 2, and Mitsuko Uchida in Mozart sonatas -- quite a range. But Rudolf Serkin’s performance of Mozart’s Piano Concerto 25, with Claudio Abbado and the London Symphony Orchestra (Deutsche Grammophon 410 989-2), provided a particularly fine illustration. Serkin’s supple arpeggios, somewhat damped trills, and the accompaniment of the flutes and violins, made for decorously merry listening. When the full orchestra joined in the first tutti, a Jovian thrum and weightiness came through, evoking a sweet gravitas that only Mozart can. The Fisher 50As did especially well with the bass viols in the first movement, Allegro maestoso, their lightly bowed notes sonorous and fulsome, filling the woofers of the right speaker with a warm vibrance that seeped away into the books of poetry and philosophy that line the shelves along that wall. But, again, it was Serkin’s arpeggios and trills in the long expository passages of this music that stirred me, his interpretation so elegant, genial, and accomplished. The Fishers rendered all of these, and each of the orchestral tuttis as well, with a fine and formidable ease, never once losing resolution, force, or grace.

So far, so good -- tone, tone, tone. What about imagery, soundstaging, and that modern thing called PRAT (pace, rhythm, and timing)? For these I went south, to Cuban son montuno, and East, to Russian Modernism.

"Yiri Yiri Bon," from Eliades Ochoa’s Tribute to Cuarteto Patria (CD, Higher Octave World 49640), is a feast of Cuban son music, with what seems a small orchestra of rhythm instruments. The lead guitar and vocals, tres, claves, maracas, güiro, bongos, and stand-up bass come through with terrific clarity and sparkle. First comes the intro, on lead guitar; then, after the startling rap-rap of a ringed finger on the wooden side of a güiro held up to the mike, the son kicks in with the full group -- guitars and tres strummed and plucked, bass thumped, claves tapped, maracas rattled, and a gorgeously intricate jarabe on the bongos. Then, over the ample tide of this Cubano sound, Ochoa cries out a tremulous, warbling "¡Yimboró, yimboró!" My entire room completely coupled to the speakers, the sound at times seeming like full surround rather than directional -- and yet, when I wanted to, I could identify the position of each instrument in space, and the male chorus spread out across the rear of the soundstage. The Fisher 50As presented what could have been a welter of percussion instruments and all their various timbres with fine imaging, a good lateral soundstage, tremendous PRAT and sparkle, and complete alacrity and precision, along with their characteristically saturated tone.

The famed Russian conductor Valery Gergiev conducts the Kirov Orchestra in one of the most stirring recent recordings of Stravinsky’s Le Sacre du Printemps (CD, Philips 289 468 035-2). It’s a fine disc with which to test the sonic palette of a system, and particularly of amplifiers. In Part One’s Introduction and The Augurs of Spring, Stravinsky’s modernist ballet seems at first a series of exquisite miniatures, as the bassoon, flute, and oboe take their brief solos. Then the dance begins with a series of sharp, pulsing, bowed strokes from the strings that are full of eccentric, thrilling accents and stirring fortes. After the first fanfare and initial blast of bass-drum strokes, a spinning drama builds among the horns, strings, and woodwinds, which share and alternate in taking the theme. The Mock Abduction culminates in assaultive, elephantine crescendos -- the horn, woodwind, string, and brass sections swell to the edge of shrieking cacophony, this rapidly followed by a series of thunderous strokes on the bass drum that could be the death of an ordinary amplifier -- if not in tonal accuracy, then in the congestion of timbres; if not in a shallow, shrunken soundstage, then in the faintness of bass slam and speed.

I’ve heard solid-state amps achieve such slam, but not without sacrificing tonal color and treble clarity. And I’ve heard tube amps deliver the sparkle, but without the slam. The Fisher 50As reproduced all of Stravinsky’s compositional complexity as manifested in this magisterial performance without shying away, with no diminishment of orchestral flavors, and with thundering blasts of bass drum and timpani. When I listened at moderate levels, my handheld RadioShack SPL meter measured the peak output as topping out at 95dB on the bass-drum strokes, confirming what, at that first stroke the first time through, my gaping mouth was already saying: Wow!

A question remained about voices. I brought out recordings by sopranos Renata Tebaldi, Maria Callas, and Victoria de los Angeles. I ended up gravitating to "O mio babbino caro," from Puccini’s Gianni Schicchi, sung by de los Angeles, with the Orchestra of the Rome Opera House conducted by Gabriele Santini (LP, Angel/EMI AV-34048). This is one of the great soprano arias, and de los Angeles sings it with moderate vibrato and long, full, expressive notes. It’s a touching interpretation, and the Fishers rendered it with purity and smoothness. So often with recordings of sopranos, one hears only the voice, not the singer’s body -- the diaphragm and midsection, which provide the foundation for the voice. With the Fisher 50As, I felt as if I was hearing the full creature -- all of the loveliness of de los Angeles, with no plaintive tinniness or shriek. Her top notes were full of dynamism, whether in attack or diminuendo.

Comparison and conclusion

The Air Tight ATM-2 stereo amplifier, itself an audio classic, albeit a more recent one, has been my reference for over two years. An 80Wpc, high-current, push-pull design that operates in ultralinear class-A/B, it generally has served me wonderfully, especially in combination with Sonus Faber’s Grand Piano Home speakers. However, the Von Schweikert VR5 HSE speakers have revealed characteristics of the Air Tight that the warmish Sonus Fabers had left hidden.

Frequently, and especially with orchestral music, I heard brightness and a kind of "mail-slot" effect in the Air Tight’s sound -- as if the top and bottom of the full range of frequencies had been chopped off. The Air Tight didn’t produce anywhere near the bass and slam of the 150Wpc, solid-state PBN Mini-Olympia amp I’d reviewed last year or the 40W deHavilland Fisher 50As. There was also a slight overdriven quality to the treble: a decided lack of silkiness and a somewhat grainy top end. I would have liked more body and midrange warmth, too. My notes on listening to some of the same orchestral recordings and piano concertos mentioned above tell me that, through the Air Tight, the violins were slightly glossy (though not bleached), timpani strokes were soft, and timpani rolls were muted, more midrangey than deep bass. I wrote that crescendos tended to lose refinement and articulation through the Air Tight ATM-2, confusing the VR5 HSE speakers. To say that I was dissatisfied is an understatement. I felt frustrated -- I’d upgraded my speakers, and now my reference amp no longer seemed to be the performer I’d thought it was.

But with operatic and choral voices, particularly tenors and sopranos, the Air Tight was superb -- clear, clean, extended highs, pretty on top, and very liquid. Always lovely with singers, the ATM-2 worked exceptionally well with the Thor TA-1000 Mk.II or deHavilland Mercury 3 preamplifiers and the Von Schweikert VR5 HSE speakers.

Yet, overall, this was a no-brainer -- whatever the Air Tight ATM-2 could do, particularly with voices, the Fisher 50A monos could do at least as well. And what the Air Tight could not deliver -- tonal weight, midrange warmth and body, bass slam and definition, a full sonic palette -- the Fisher 50As delivered in spades. The Fishers and my Von Schweikert VR5 HSEs seemed a perfect match.

If your speakers can get by with relatively moderate power (40W nominal, perhaps 45W at clipping), you should strongly consider auditioning the deHavilland Fisher 50A monoblocks. Their combination of top-to-bottom balance, clean and resolving highs, magnificent bass and slam, articulate speed and PRAT, and gorgeous brocade of sound, seems to me very hard to beat. In fact, I couldn’t beat them. I gave in to the music, sold the Air Tight ATM-2, and bought the review pair of Fisher 50A monoblocks. They took me back to the future, and I’ve never been happier with my system’s sound.

. . . Garrett Hongo

deHavilland Fisher Model 50A Mono Amplifiers
Price: $7250 USD per pair.
Warranty: Three years parts and labor.

deHavilland Electric Amplifier Co.
2401 NE 148th Court
Vancouver, WA 98684
Phone: (360) 891-6570

E-mail: 6sn7@abac.com
Website: www.dehavillandhifi.com

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