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Despite this extreme treble suppression, the Colotube sound particularly with an ultimate tweeter like the Raal was anything but dark however. It was very billowy, fluffy and airy in fact. Transitioning to my white Serbian amps altered that. With them self noise decreased to zero (in my room which is rather smaller than Dan's, even 91dB speakers transmitted some hum with the 300B). With the small pentodes diamantine brilliance and an accompanying hue of bluishness increased. This enhanced retrieval of what I call gossamer stuff. Think iridescence and tintinnabulation. Simultaneously—and remember that I deliberately specified the IT-coupled Kaivalyas as true pentode amps which Sasa Cokic implemented with two ultra-minimal local feedback loops—the white monos shored up overall gestalt. The bed sheets were tucked in on three sides rather than hung loose over the edges.

Where the Colotube amps wafted to feel spatially expansive and unmoored—strangely a certain amount of tube noise can act a sort of dither to emphasize this quality—the Kaivalyas were more focused down and anchored. The no-feedback single-ended direct-heated sound was sweeter and more radiant. The low feedback push-pull sound was more separated out, distilled and taut. These type of poetic descriptions drive engineers up the monkey pole. But how else to point at very real performance differences that don't bluntly revert to frequency response charts? If one didn't fuss to go instead with the first thing to mind after making the switch from EL84 to 300B, one would simply say that the 300Bs sounded bigger.

If one felt compelled to inquire why and carefully inspected this impression over various music samples, one should arrive at something like the above. One might even fall back on the oft-cited inner radiance of triodes. Working from the inside out, radiance reinforces the impression of expansiveness or scale. This explains why despite diminished light on the very top this still is a very lit-up sound which doesn't rely on the last degree of effervescence. It's not a function of ribbon-type super tweeter behavior. It's about how the vast majority of the sound appears, not a very small fine fraction that's often overwhelmed by heavier action in the first place.


By now the core appeal and distinctiveness of the Colotube amps should be clear. Their lithe illuminated aerated qualities have far more in common with quality 45 circuits than most 300B implementations. It's only a guess but a big reason for this must be Jac van der Walle's buxom 20A driver tube. I've not encountered it before anywhere but reading his descriptions makes clear that he intentionally designed this driver tube for exactly this type of application. To my ears it finally moves traditional 300B sound out from antiquity into the 21st century. By the same token those married to the 'quintessential' queen of triode sound could find the Colotube version too light and fresh. I presume Kondo then would be more applicable. There are remnants of octave-doubled THD here but those seem quite diminished. It's fair and poignant to think of Gino's amps as 'high-power' 45 SETs with just a minor downshift of the tonal center of gravity. But even a paralleled 45 would still make only less than half their useful power.


In use, the rear-mounted mains switches right above the power inlets should only bother those who'd install these amps in a rack where they must reach behind them.


It's skin oils from handling that will put the usual lie to steel's 'stainless'. Like Art Audio, Gino doesn't use a clear sealant. You'll have to remove finger prints with just the right industrial agent. Good luck. For any expensive electronics (which these unapologetically are), I'd never specify stainless steel because it'll never again look as pristine as it did new. Chrome does handle better but requires care not to burn in swirl marks - and it shows up dust more and is very expensive to have applied with Harley-type quality. Stainless steel it is then.


Conclusion. Swiss hand labor is costly. Premium parts cost money. 10 watts are limited. And there is some self noise. If those realities don't conflict with your budget and ambitions, Gino Colombo's 300B single-ended monaurals are everything they should be for a modern listener who expects resolution and linearity as premium transistor amps have established but then wants that elusive X factor. Satisfy inherent demands with copasetic speakers like the Aries Cerat Gladius or Voxativ Ampeggio and there's no way anyone listening from behind a thin black curtain could point at coagulated triode distortion, homogenization, portly reflexes or ponderous fuzzy bass. Instead there are terrific microdynamic reflexes, vast staging and tonefulness that's realistic rather than overdone. While experienced listeners should eventually suspect tubes, I'd be very surprised if they could/would properly identify 300Bs. No way. That's how much these amps diverge from their archetype of popular (and justified) perception.


Reactions to that accomplishment will depend on alliances - to the archetype or to hopes for something more modern. This listener considers the implementation here a full and rare realization of the tube's true potential.
Quality of packing: Card board with foam cheeks.
Reusability of packing: A few times.
Ease of unpacking/repacking: A cinch.
Condition of component received: Flawless.
Completeness of delivery: In person as is standard for Switzerland.
Human interactions: Very good.
Pricing: Artisanal high-end, i.e. expensive but in line with current conventions.
Final comments & suggestions: Colotube Amplifiers sells deliberately direct only to eliminate dealer/distributor markups. Potential clients are invited to audition the amps in the designer's home. Pickup from three different Swiss airports and one night of accommodation in the Colombos' guest suite are offered free and up to CHF 700,- in travel expenses can be applied towards a purchase.
Colotube website
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