This review page is supported in part by the sponsors whose ad banners are displayed below
In Villeneuve: At 86dB sensitivity and 3-6Ω impedance, no matter how upscale the amp's providence, you would not mate Mark+Daniel's Fantasia-S two-way to a 10wpc 300B SET. Even so the foolhardy must try. It worked surprisingly well. Naturally I had to increase the gain setting of my Esoteric preamp and run it over the last quarter of its range. That's expected. In a 11.5m long room where the seat is about 4 meters from the speakers, achievable loudness well exceeded what would be acceptable for thick-walled town house conditions. But clearly the low bass the Fantasia-S generates with my 100wpc ModWright KWA-100SE transistor amp was now bloomier and less striated though not really less extended.


The prime reason to call this match sub optimal were two giveaways. At low volumes the sound wasn't as resolved and easeful as it should have been; and the general quality of effortlessness was compromised. It lacked the organic breath I'd heard at Dan's. Rather than falter much on audiophile measurable qualities (bandwidth, linearity, low distortion) it faltered on more immeasurable attributes. This confirmed why one shouldn't attempt such a mating if perhaps not for exactly the reasons most would suspect. In its most basic form, playing loud enough without apparent distortion isn't the same as playing at the top of one's game.

Enter the Cypriot Gladius from Aries Cerat. A 12" 3-way with Alnico mid, Raal ribbon and broad/shallow stacked-Ply cab with wind-tunnel bullet head, it runs an external leatherette-covered network box with acrylic screen and very large transformer-type inductors.
 
Midrange filter
As the Gladius plot shows, its massive Acoustic Elegance woofer with Lambda motor is loaded as an acoustic suspension or sealed alignment. The plot's 6.5Ω nominal impedance thus lacks the wild saddle response and steep phase angles of ringy ported schemes. It also never falls below 4Ω. Given that Aries Cerat specializes in SET valve electronics, one expected such designed-in benign drive.


My most splendid Colotube results reconfirmed how it's this behavior which is most relevant to any truly successful low-power no-feedback pursuits. Actual voltage sensitivity—here a true 91dB—is a far second. Instant as though flipping a light switch, acoustic proof of interface happiness came by way of two items. First and most profoundly, the gushing liberated waterfall quality had gotten reestablished as though in response to that Bing Cosby song "Don't fence me in". It now also tracked unbroken down into subdued playback levels.


Two, low bass (inherently not as extended as with my Mark+Daniel or ASI Int. speakers due to the sealed loading) was texturally continuous and as such as elastic and boisterous as the midband. Popped foundation lines on Caravan Sarai's Walking to Kashi—this is right up there with desert world beat classics One and Prayer for the Soul of Leyla by Jamshied Sharifi—didn't alter their texture as the bass player skipped back and forth between two or more octaves to lay down a tight groove. Ditto the Hadouk Trio's Lou Ehrlich and his funky gumbass. These examples had little patience for popular claims that SET amps can't do proper bass. The Gladius woofer with its underhung voice coil, impulse-optimized loading and group-delay tweaked crossover followed orders with snappy salutes. The only noticeable item not on the menu here was complete 1st-octave coverage. That was a deliberate quality-over-quantity decision by speaker designer Stavros Danos who wanted a still moderately sized enclosure. For reference, the famous didgeridoo on Dead Can Dance's Spirit Chaser was reproduced in full glory however.

To go straight for the jugular, the Colotube sound with appropriate speakers wouldn't recognize pipes and slippers if you spelled them out. Then it's an electrifying and energized sound of speed, high pop and incisive articulation. A close-mike'd bowed electrified sarangi for instance has all the raspy grittiness and twangy bite that make this traditional Indian instrument so fiercely modern. Percussion where the player physically taps a microphone with his hands has all the cayenne pepper such direct coupling implies. Unlike fast class D amps whose ultra-low output impedance creates a drier whiter very damped sound, the Colotubes have more blackness in their palette and are more billowy of gestalt. The blackness makes for properly saturated cinema colors with the necessary half tones. Your sound won't be an Electric Avenue telly whose contrast and sharpness settings are pushed up to 100.


Properly set up where speaker path lengths to the seat are matched to within better than 0.25" with a laser, a richly fanned soundscape with multiple depth layers will have spiky percussive elements and emphatic performer actions jump out like embers from an open fire. This is the opposite of homogenization or thickness which zero NFB triodes are often accused of. Such live-wire twitchiness relies on excellent microdynamic reflexes and speed. It also relies on a low level of harmonic distortion which particularly in the usually exaggerated 2nd tends to close down the music fabric to shrink its looser weave together. Presumably the DHT-drives-DHT circuit creates some deliberate distortion cancellation. Whatever the reason, this sound exhibits significantly lower 300Bness than usual.

   
But this triode plus über driver still couldn't do the uppermost treble. My Kaivalya monos with Russian military 6P14P-EV (an ultra-spec EL84 equivalent) playing "Promenade" from Vassilis Tsabropolous' Melos showed how the Serbian ribbon tweeter with amorphous-core transformer now captured the triangle with far more inner energy. "Like diamonds" my wife opined. Perfectly put too - hard, refractive, pure, sparkling and scintillating like an expertly lit diamond with inner fire. Moving on to Jacques Loussier Plays Debussy, drummer André Arpin's spiderwebby workout on cymbals confirmed it.


With a fast and very extended tweeter like the Raal, the 300B simply cops out on ultimate extension. I suspected this for years. Testing a wildly more expensive such amp than previously reviewed simply settled it. The so-called queen of triodes has a soft top no matter what. Where this one excelled however was on Loussier improvising solo on Chopin nocturnes. During certain mostly true-to-score rubato intros prior to his dreamy staccato Jazz morphs, the sense of viscosity whereby individual tones without damper pedal felt like bubbles slowly bursting in oil was fantastic. Krystian Zimerman performing Rach 1 & 2 with the Boston Symphony under Seiji Osawa stressed again that the Colotube amplifiers love piano with just the right tonal voluptuousness and material heaviness.


Due to not fully teasing out the upper harmonics whilst making a U-turn into a different genre altogether, e-guitar distortion with its overdrive harmonics lacks some nails-on-chalk-board nerve. While that might arguably not be high priority for DHT aficionados, it's fair to mention that despite their accelerated shot of double espresso in general, the Colotube tonality retains that recognizable 300B trait. Compared to a more upwardly ambitious 45 for example—or a common 6P14P-EV in class A pentode mode—the very top clouds over mildly and with it a degree of overtone finesse and brilliance.
Enlarge!