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An experienced audio engineer once explained to me how come tube watts "sound more powerful" than transistor watts. He talked about ratios, of how relatively small input voltage fluctuations modulate ultra-high plate values that, in 845 or 211-type amplifiers, could mean 1400 volts on the rails and 700 volts on the driver/input stage. It seemed a very sensible argument that this tiny/vast juxtaposition would net a both very linear and dynamic transfer function and leverage advantage.

845 lore has it that once these transmitter-type bottles (virtually identical to 211s except for turns ratios) operate above 1000 volts, they enter their G-spot zone to perform on a higher plateau. How to design a reliable and quiet amplifier that runs such voltages is, naturally, a different subject altogether and one we expect becomes a pretty advanced subset of tube amplifier design. Where exactly do you run the tube for lowest distortion vs. max output power? The meter-based bias adjustment of the Ios allows the end user a bit of a window to tweak final sonics. To guarantee extended tube life, you should of course obey DeHavilland's recommendations for max bias current for each 845 type. They generally run around 70 milliamperes but some might want to see 55-60 instead [ca. 9:00 o'clock on the bias controls]. DeHavilland does not believe in active power supply regulation to keep their high voltages as confined as possible. All regulation is achieved passively the old-fashioned way. This is offered as one of the reasons why these amps are so reliable. "Overbuild the power supply and it won't need excessive regulation" seems to be one of Kara's credos.

My acid noise test netted surprising results. The Ios wasn't dead quiet but produced such low hum levels on the 101dB Definitions that I could not hear them at all in the listening seat. While in that setup and using the M-type 845s, I observed next that the Ios mirrored the general sonics I've come to expect from 845-based amps - big and dense, with a billowing top end and excellent midbass attack and crunch. Compared to my op-amp based AudioSector Patek SEs, this density of images and compaction of musical molecules was more similar than not though the Ios went farther yet. But the main qualifier instead became the relative acuity of transients within this solidity. There the Pateks retained more incisiveness or apparent articulation, making the SET sound thicker and more lethargic. This wasn't so much because the actual image density was much higher but because leading edges became far more enveloped rather than remain spiky.

One of the fondest tube memories I retain from amps that have passed through my review system is that of the Canadian Wyetech Labs Sapphires. Those are unusually wide bandwidth paralleled 300B monos for 18 watts of very linear, dynamic and exceptionally articulate performance. In the overall landscape of tubes, the Sapphires would be considered slightly lean yet very fast and supremely detailed. In this same landscape, the M-tube fitted Ios is the more languid, rotund and looser rather than snappier of the two.

Being all relative values grouped like spokes around the theoretical neutral hub, these aspects gain in prominence the farther they move away from center. The density spoke moves from lean towards portly into fat. The complimentary opposite detail spoke corresponds by progressing from transparent towards varying degrees of opaqueness. The spoke of apparent speed slows down as you move towards the circumference. And so on. The circumferential rim acts as the unifying principle or boundary of this field of qualities. It reminds us how all of these apparent values or attributes are interrelated. They often are merely various facets of the same thing. Apparent speed, detail and transparency are clearly interlinked, for example. Alter one and the other two are affected.

While I wouldn't call the Ios slow or fat per se, its general character during my first encounter was certainly significantly more developed in those directions than my AudioSector amps or, even more pronounced and opposite, the far more solid-statish and affordable, ultra-transparent and fast Decware Zen Taboo. It's easy to get trapped in generalities as they relate to tube type. The aforementioned Sapphires rather defy stereotypical notions of 300B amps. They raise the question whether the stereotype really fits the tube. Or is it rather a qualifier for compromised implementations? If those are common and numerous enough, they become the archetype by default. The majority rules even if it is the lowest common denominator.

Against this background, the Ios did initially conform to expectations raised by the Art Audio Carissa on my then Avantgarde Duos and the long since discontinued Bel Canto SETi 40 from even earlier. You see, I relate to the 845 sound thus far (if such a thing really exists) as one that's massive, slightly thick, very developed in the bass yet with good treble extension. By the same token, I wouldn't call it a paragon of detail, PRaT or adrenaline. I'd call it juicy, slightly euphonic, a bit slow, slightly foggy and very solid. And did I mention the obvious yet? Both the bright glow and whitish content therein -- as well as our knowledge of high internal voltages -- tell us how very hot these tubes do run. They throw off heat by the Fahrenheits squared. Even the spades of my Zu Cable Ibis were quite warm to the touch when I disconnected them to switch to the Pateks. The Ios thus makes certain demands of its would-be owners. It's big, it's heavy, it's pedestrian in appearance (at least prior to the appearance of the tube cage) and it doubles as an exposed space heater.

Before listening further to the Definitions and getting caught up in prematurely type-casting the DeHavilland amp, I needed to switch to the Gallos as the kind of load this beast was really designed for. It'd avoid running the Ios barely in 1st gear. After all, as a medium-power amp, it stood to reason that its max torque curve would kick in a bit later than the quarter or half watt I was using as the median value on the Zus. In with the Ref3s then.

Still using the M-type bottle, the main personality of the Ios translated in fact, just slightly less so than before. It was still relaxed, slightly soft, very smooth but, for my personal tastes, not quite energetic or definitive enough. As I had already tested on the Zus by disconnecting the rear-firing woofer array (simply pull the power cord), the low bass texture of the Ios didn't quite match its upper bass sock, feeling less articulate and more indistinct down low where I could have wished for more charged transients (something where the Gallos admittedly thrive on current).

Switching to the B-type Super TNT-labeled bottle addressed the attack articulation issue very nicely and also seemed to give more growl and menace in the bottom end such as is called for on Stellamara's
fabulous new The Seven Valleys release [Hearts of Space 11417]. It mixes Moorish and Medieval styles in a Vas-reminiscent setting filled with dark undertones, lead signer Sonja Drakulich sounding like a tribal soul sister to Azam Ali and at times even Irina Mikhailova. String virtuoso Gari Hegedus plays anything from oud, mandocello, divan saz, Turkish banjo, baglama, cura to sarod, Tambura, violin and viola. Plenty of Middle-Eastern and African percussion and ambient keyboards help erect a moody, shadowy atmosphere that captures aromas from Sufi zikrs to Melchite lithurgical song to neo-tribal outings Lisa Garrard-style.

In a somewhat related vein, the glorious harmonizing of Catalonian Gipsy vocals on Kaloomé's Sin Fronteras [Long Distance thru Harmonia Mundi] from the Perpignan region in Southern France was next. It gave full credit to Antoine 'Tato' Garcia's sharp lead guitar and Guillaume Bouthié's rumbling bass. As with most things audiofile, initial impressions can often be misleading unless you've optimized the amp/speaker interface and -- with tube gear -- have experimented with certain rolling options. In this instance, I'm definitely a B rather than M man. It's a hear-right-away unambiguous preference between the two Shuguang 845 options I had on hand. The M tube is too smooth and listless for my tastes. I need more spunk and "edge".

Once the B valve had catered to my proclivities, I was a very happy camper indeed. I finally got the DeHavilland magic I'd gone repeatedly on record about with various show reports - in my own crib. Now the rumba Flamenco-flavored strings blistered with metallic fire flies and the half flageolet/half fundamental edge-walking on the violin came across with all the implied dirtiness and higher harmonics that makes this style of playing (typical in Greece and Turkey for example) so hair-raising. Ditto for the guttural Khaled-reminiscent Algerian vocals of Madjid Benyaoub whose Arabian style blends wonderfully with the Gipsy Kings-related singing of Antonie and Sabrina Romero who together make up the vocalists of Kaloomé. Everything now had drive, energy to communicate passion and raise hackles.

That's why I fancy Gipsy and ethnic music. Their singers don't do pretty. Instead, they cry, warble, croak and in general go for the gusto, civilized polish be damned. It's this energy that a component either liberates and communicates or holds hostage. In my book, nothing on the fancy-pants list of audiophile attributes matters if that energy doesn't come across. If it does, I can easily forgive other flaws. If it doesn't, the discussion is over before it started. Boredom and tame aren't what I listen to music for. The M-sound fell into the former category. I would have written off the entire amplifier because of it. Fortunately, Kara and George gave me an option. It completely turned the tables - an important reminder for reviewers and audiophiles alike that the devil's in the details. Much money can get wasted (and many errors of judgment committed) if all of us don't go the extra inch or mile. We must do as the car mechanics do - track a problem through a process of elimination until we isolate the culprit or give up and proclaim the thing beyond repair.

Post transformation, the DeHavilland firmed and sped up without losing that massive solidity we expect from high-power push/pulls. The slightly suffocating earlier density thinned out just enough to increase detail and edge definition but retain that reach-out-and-touch factor that distinguishes flesh-and-blood beings from see-through ghosts. Bass on the Gallos was just slightly on the bloomy side but still well within the realm of control rather than looseness. Vocals were fully integrated into the fabric rather than assume that stand-out highlighted mien of deep triode. I could detect no overt textural discontinuity between registers, suggesting a very linear amplifier that spreads its particular personality evenly from bottom to top. That language reversal was deliberate. If anything, the Ios seems just a skoch dark because of the overall heft and chops in the lower registers. It builds its sound from the bottom up. Mind you, there's plenty of treble energy. But rather than seem airy, the amplifier's overriding attribute is that of a charging bull - mass in motion.

That combination completely prevents zip and hype which can occur when motion is wedded to insufficient mass. The image of the bull is doubly fitting as it also suggests sizeable cojones i.e. drive. The Ios manhandled the Gallos without a glimmer of stress or sweat. The only thing lacking on the ultimate scale set previously for the Gallos by the ICEpower H2O Audio monos was low bass amplitude and definition, precisely why Gallo authored the supplemental bass amplifier (which is finally in production). Unless you have current champs like a big Bryston or McCormack that could make the SA amp superfluous, tube amps nearly by definition will not get maximum sub-40Hz bass from the Reference 3s whose long-throw woofers are loaded into a negligible sealed air space and naturally want to roll off right above the lowest octave.

Though 25 paper watts may seem a bit skinny in a market that uses power ratings to impress insecure customers, the Ios is clearly plenty potent to handle 88dB speakers, meaning the vast majority of commercial speakers likely to be owned by music lovers considering the DeHavilland. Checking bias once I'd set it in accordance with Kara's instructions (one marker below redline for the Ms, one above for the Bs), I noticed zero drift, further
cementing the amp's industrial-grade Chevy truck impression. What the Ios lacks in sex appeal it more than makes up for in balls and no-nonsense engineering. No turn-on thumps, no noise safe for a completely normal and very subdued hum on the Gallo woofers, nothing wacky or wigged-out. This amp will play very loud without closing in or exhibiting any telltale signs of compression with its attendant bite in the treble and changes in linearity.

By virtue of expensive quality iron and thus real-world drive, this DeHavilland tank allows tube lovers to shop for the amplifier rather than first speakers. As a genre, S.E.T.s mandate special considerations when it comes to what speakers they're copasetic with. DeHavilland's approach from conception has always been to design amplifiers that were far less fussy about special speaker diets. The design brief for the Ios was to downscale expense and box count from the 845G monos [above] but retain usefulness, power and sonics. While I've only heard the monos at shows and with Alon/Nola speakers, the 5-watt less potent Ios leaves absolutely nothing to be desired and. Like its namesake -- one of the southern Cycladic islands of Greece -- it is a ray of sunshine in audioland, offering top performance and fair value.

The combination of 6SN7 and 845 produces big yet clean tone in the opposite corner of dainty wallflowers. There are no specific voicing tricks to favor one music style over another. There's the clear sound of displacement-happy power. Best of all, behind the tone and power and drive rests a sense of relaxation that translates as a complete and utter absence of stress in the listener. Chrome-dome 6SN7s such as were provided for this review are considered a very worthwhile upgrade but I can't stress enough how the amplifier's core character seems critically sensitive to what exact 845 output tube you chose for your specific system context. Unlike me, you might favor the M-type 845 but chances are, you'll have a clear preference either way so do try 'em both.

In closing, the DeHavilland Ios is the Clydesdale in the S.E.T. stable. It's very muscular and strong, well-tempered and quite literally a workhorse rather than Arabian prima donna. If it's as reliable as reputation and build quality suggest, it'll take the fussiness out of the equation so more people can join in the very real joys of single-ended triodes in a sonically and mechanically super-robust fashion. A matched pair of Valve Art 845s can be had for as little as $82 so you're not looking at a financially upsetting triode habit either. And I bet that once the optional tube cage is finalized, it'll add just the right amount of visual pizzazz to also bring the cosmetics fully into the 21st century. All in all, the Ios merits a very high recommendation just as all my prior show encounters of
its older siblings had predicted. But then nothing beats personal experience in one's own system. I'll henceforth think of the Ios as designer comfort food. It's solid, nourishing no-fuss fare with just the right amount of sonic sophistication and resolution to make the grade for both finicky chi-chi eaters and meat'n'potatoes music-first lovers. Bravo to Lady Kara! She's clearly someone who, while firmly grounded in the engineering aspects of her craft, has mastered the art of designing with her ears. As she explained in an e-mail to Michael Lavorgna who reviewed her UltraVerve Junior preamp, she trusts the spontaneous responses of her own body to tell her when a design is finalized. Does the internal judge stay on patrol or move out of the mental picture? Does the body tense up or relax? With the Ios, the only thing to remind you of electronics rather than music is the bright light and heat. [Incidentally, George reports that quite a few 230V DeHavillands have already shipped to Asia and Europe with zero 50/60Hz hum problems so the DeHavilland sound is now ready to go global.]
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