Downstairs. I started with Vivace to read overall system integration which was exceptionally lucid and sorted to present a tad lean. I eyed the Vinnie Rossi preamp with its out-to-900kHz direct-coupled power triodes. In just then were Elrog ER50 'super 45'. Those departed in favor of Western Electric 300B. Voilà, that small twist on the steering wheel created a most obvious course correction to show just how low Vivace's self sound was. It took no big dose to 'overpower' it. A small upstream alteration registered unequivocally. In an instant I sat in my ideal zone of perfectly coordinated speed:body and transparency:density markers. With all four AGD monos live, it just took moving over XLR interconnects and speaker cables to conduct easy A/B comparisons.

The deep orange illumination on the monos here is overlaid from a night shot. In the actual room lighting shown, you'd only see it faintly.

Reseating cables repeated the upstairs showing. Audion was the fresher and more upfront, Vivace more laid back and deep. Depending on material, I could fancy Audion even more. Take ensembles like Dan Gharibian's newer trio. It shrinks down the former Bratsch group to just three. The resultant intimacy, of a Gauloises-weathered voice accompanied by guitar, accordion and final whistling, felt more intense by a click or two whenever Audion sat in the driver's seat.

Where Audion and Vivace overlaid completely and indistinguishably was in their phenomenally lit-up quasi holographic soundstaging. Their joint show was about fully developed audible space and the attendant hear-a-pin-drop perception that nothing whatsoever remained obscured in any remaining noise floor. Like upstairs, the primary focus was on the mid-to-upper bands. Those felt uncommonly shiny, brilliant even depending on recordings. Upon inspection, the low bass was just as adroit and illuminated. Absence of all darkness simply bled out from the lower registers any sense of that extra weight, emphasis and/or striated wiriness which much class D injects. Rather than play chief attraction for any otherness from conventional amplifier topologies, AGD-style low class D bass fell in line behind the mid and treble bands. It was always present to play its immaculately detailed supporting role but never stepped out for a selfie. This supplementary inclusion of the bottom registers added itself to the overriding sense of speed and shadow-less clarity to describe the sound's sum total. The special Audion wrinkle was preventing its energetic forwardness from getting aggressive or edgy. The primary sense of distinction for Audion thus was that its light seemed to come from stage back toward the listener. With Vivace, the lights originated behind the chair and lit up the stage from the front. That's not meant literally, just as another pointer to suggest a small difference of perception.

Just as I had during CanEver's Olimpico review preceding AGD's, I again wondered. Mario CanEver's smaller amp is priced at half of what his flagship commands yet uses the exact same signal-path circuit just like Alberto's two do. The only difference for the Venetians is the power supply and 20 watts less power. Didn't that destine Mario's smaller amp to steal big-brother sales? In CanEver's case, I didn't get to hear the bigger amp. I only had its specs and pricing. Alberto instead elected to ship me both models. That merely heated up the same question to boiling point. For the kind music we play and over the speakers we do, I didn't experience Vivace as superior at all, just different – and even then not by much. Again, my assumption is that once the KT150 GaNTube bows, Vivace will get rewired to high-power mode to differentiate itself properly and build out its desirability profile. For now, the smart money should invariably focus on Audion unless someone simply wants Vivace's looks.

A friendly class A/B+D fracas involved our 1MHz LinnenberG Liszt 200-watt monos. After simpler more quiet material to get a fix, one of the complex more challenging tracks came from Acatao by fusion group Indialucia. It led to an obvious verdict. Vivace was equivalent to our best high-power traditional amplifiers but not identical. I noted three telltale distinctions. If we call tone the overall sensation of texture, the German monos played it a bit fuller, weighty and juicy. In the bass they were more massive but also bloomier so not as preternaturally controlled and finessed. Finally came silence as the three-dimensional canvas in and against which sounds arise. Here the Germans were wetter. Explaining it isn't easy but visualize the very first onset of heat shimmer. It's when in a very hot summer, agitated air becomes visible. Causing no blur or flicker of images—no desert mirage—this quasi dither gave the emptiness/silence between and around the images a particular tangible presence.

Vivace by contrast gave emptiness a sense of absence. That worked like negative space in a shadow play. It created even greater contrast ratio but also an overall drier less breath-infused feel. Extricating possible cause in tech terms, what suggested itself for Vivace was an even lower noise floor from its switch-mode power supply; even lower output Ω; and even lower phase shift in the low end. Decisive was its equality in the upper bands. My standing class D complaint about its clearly less suave top end had curled up and died. Compared to our fastest most lit-up class A/B amps, Vivace and Audion were equal. If I owned either AGD and wanted to equalize its tone weight with that of our LinnenberG, I'd revert to the original—more organic less resolved—FPGA card of our Denafrips Terminator DAC. If I wanted to equalize textural wetness, I'd run NOS Western Electric direct-heated triodes for class D, modern Elrog for class A/B. Voilà, ten minutes later I'd have class D monos perfectly on par with our €8'500/pr LinnenberG, albeit with the lovely advantage of even more adroit 'fast' bass.

As Alberto Guerra said earlier, "most readers/users are familiar with Hypex, ICE and Pascal boards which, as far as I know, are all based on silicon Mosfets. Moreover, they all have a specific engineering and marketing goal which is to achieve the highest power for the lowest price. This creates very big economies of scale to push their adoption across more and more of the industry. They tend to offer good performance and provide a certain level of standardization. But that wasn't my goal. My true goal really wasn't very humble. I wanted to remove the stain attached to class D for being an inferior topology that's just good enough for car audio, MidFi or DIY. The fact that I chose such a peculiar visual design should give ample indication that my product and marketing strategy are a bit alien…"

So they finally landed. And they definitely, categorically, undeniably removed the stain. These are the good benign very advanced aliens. It comes with their terrain that this would no longer be about the highest power for the lowest price. If you want to play there with GaN, an Orchard Audio Bosc is one place to look. I simply don't know about its performance. With Alberto Guerra Productions' Audion and Vivace, I do. They are about highest performance, period. Their novel tubes aren't vacuum tubes but complete output stages with gallium-nitride Mosfets. They can be replaced and/or upgraded as AGD make further advances. With a high-power KT150 GaNTube already in the works and a lower-power EL34 mentioned for eventual headfi, we've only seen the first manifestation of this concept. And what a concept it is.

Hence the award's byline. GaNTube class D is for very discerning listeners groomed by top class A, class A/B and direct-heated triodes. None of these topologies or output devices are passé. Due to low power efficiency, class A simply carries a 'green' penalty now. And class D is no longer synonymous with "power is cheap" as the tired argument wielded whenever purveyors of very inefficient speakers make excuses for their lazy designers. There's plenty of that type class D around.

Today's Audion isn't that. At 85/170/340W into 8/4/2Ω, it's technically not even a muscle amp, just a mid-power specimen. And it's certainly not cheap. But it's half the price of Vivace and its most affordable competitor at Merrill Audio whose bigger models demand a cool €24K and €38K. That's the company AGD's Audion keeps. And that has it stand out on this first day of 2020!

To learn how this story continues, we've already been promised the Andante PreDac & Vivace Plus monos as soon as they begin shipping…