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This review published in August 2022 on HifiKnights.com. By request of the manufacturer and permission of the author, we syndicate it here to reach a broader audience. – Ed.
Reviewer: Dawid Grzyb
Sources: Innuos Statement, LampizatOr Pacific with KR T-100 or LV 300B and KR 5U4G
USB components: iFi Audio iGalvanic3.0, micro iUSB3.0, 3 x Mercury3.0, iPower 9V
Preamplifier: Trilogy 915R
Power amplifier: Trilogy 995R
Speakers: sound|kaos Vox 3awf, Boenicke Audio W11 SE+
Interconnects: Boenicke Audio IE3 CG
Speaker cables: Boenicke Audio S3, LessLoss C-MARC
Power components: GigaWatt PC-3 SE EVO+ w. LC-3 EVO cord, LessLoss C-MARC, Boenicke Audio Power Gate, IOSL-8 Prometheus
Rack: Franc Audio Accessories wood block rack
Network: Fidelizer EtherStream, Linksys WRT160N
Retail price of component: $5'000 for preamp, $5'500 for amp in standard finish
In anticipation of this review, I penned an editorial on imitation being the sincerest form of flattery when it comes to AGD's unique GaNTube™ concept. – Ed
The Tempo and Alto are the AGD Production company's latest entry-level arrivals. Word is, they're not far off from their costlier siblings. Now it's time to investigate whether that's true. AGD established in April 2015 in Los Angeles. They're no stranger to HifiKnights or 6moons. To recap, Italian founder Alberto Guerra moved to the US more than two decades ago. Since the 1980s he's worked on new semiconductor types at International Rectifier, famous for power electronics like Hexfet acquired by Infineon in 2015; at Vishay on integrated circuits; at Semtech whose marketing strategy he reshaped. He holds a Nuclear Engineering degree and owns 10 patents, six for packaging technologies, two for novel power module topologies, two for GaN power Mosfets and IC. On top of that he worked on power applications from electric grid level to what portable and IoT hardware runs on. All things considered, the man is a highly skilled engineer with lots of experience which now includes a unique approach to class D audio circuits.
After reviewing his two mono amp models—Vivace and Audion—it was apparent that his take on class D exceeds the usual reasons associated with this topology by way of high power efficiency from a small footprint. Although he is fond of accuracy, he had a firm idea how to squash most related class D stereotypes. During his engineering career he also pursued gallium-nitride transistors aka GaN designed for switching applications. That makes class D their ideal environment. Alberto was also involved in the team which designed them for actual audio applications long before their commercial appearance in the hifi industry. As a pioneer on this front, he has the knowledge how best to implement these parts. Their list of advantages for switching applications over regular Mosfets is impressive. As very low-charge class D output devices, GaN transistors switch significant voltages at MHz speeds so are faster, wider on bandwidth and free from oscillations even at very high slew rates. All in, it's no exaggeration to call out GaN as very promising tech here to stay. Also worth mentioning is that critical gallium-nitride parts inside AGD Production amps are unobtainable. Alberto bought their entire stock like Nelson Pass did for his SIT transistors.
My introductory AGD review went live in May 2020. Several other manufacturers have jumped onto the GaN wagon since. From Srajan we learn about Hifi Rose, Merrill Audio, LSA, Orchard Audio, Gold Note, Mytek and Java Hi-Fi. That list probably doesn't end there and is still destined to expand. My experience with gallium-nitride transistors for now simply limits itself to Alberto's products. That said, after guesting Vivace and Audion, I became a fan. Both were exceptional not only given their type and price but in general. Vivace netted our Victor award because I hadn't heard any other class D amp come even close. It sounded unlike all other switching designs and is fondly remembered as a machine I'd love to one day own. Alberto's amps stomped on quite a few misconceptions of their breed and were visually radical to boot. He managed to integrate his signature GaNFet power stage inside easily unplugged GaNTube™ glass envelopes appropriated from the well-known KT88 tube.
This clever twist results in modularity that can hot-swap entire power circuits with an aesthetic flair only an Italian could pull off. Alberto's compact enclosures with protruding no-vacuum tubes look gorgeous if you ask me.
Tempo's motherboard above; power module closeup below.
AGD's mono amps were a lot to digest already but their maker's engineering expertise exceeds speaker amps. His Andante pre/streamer/phono/DAC sent my way looked the part, featured useful utilities, had a very nice interface and rendered all my standalone DACs useless add-ons. It was as uncommon as its amplifier mates and no mere portfolio filler. By then AGD's roster was two monos and one preamp deep whilst a flagship mono now known as Grand Vivace already hovered in the pipeline. I imagined that Alberto might next downscale to more affordable renders of products he already had. I wasn't wrong. Today that next chapter of the good AGD book opens. Although I didn't get a chance to meet up with Alberto during this year's Munich show, he presented his two latest designs, the Tempo stereo amp and its Alto preamp companion. Post Munich these two made another pit stop along the way but eventually a large cardboard box with two watertight and crush/dust-proof Pelican flight cases delivered in July. This rather luxurious packaging is standard and limits transit damage far better than regular boxes. The fact that today's more affordable AGD models arrived so dressed deserves two thumbs up. Each case featured a foamy interior cut to accommodate its treasure, a nice power cable, woolen gloves and a manual. The pre also came with a handy remote that looks like Apple's aluminium wand but is plastic with rubber buttons so not quite as posh. It works well however so I won't complain.
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