AGD The Audion power amps


The element gallium unnoticeably entered our daily experience in the past ten years, when indium and tin substituted mercury – toxic for humans and the environment – in the common thermometers we used to take our children’s temperature.

However, only in recent times, after the traditional incandescent light-bulbs were made obsolete, the industrial demand of this precious element skyrocketed so much as to raise the question, given the annual global production of barely 70 tons, of sufficient availability for the emerging market of LED lamps.

In the arsenide form – GaAs compound, it is largely used in the semiconductors that function in high frequency, thanks to a faster response during the commutation phase.

The current race to create high-performing semiconductors, to increase the efficiency of power supplies, and in general in all power electronics applications, has accelerated the use of compound materials.

Today, in the Nitride - GaN compound form, Gallium Nitride is slowly but steadily replacing Silicon in the manufacturing of the most efficient and smaller power stages. Gallium Nitride MOSFETs enable the design of extremely fast, more compact and efficient power-stages, and are indeed used in the amplifiers tested here.

The major production cost of those metal compounds, difficult to obtain since very high temperatures and pressures are required for their synthesis, results in the cost impact of semiconductors that benefit them, limiting their application to particular and specific contexts. Despite this data, the analysts predict for Gallium Nitride’s market in 2020 a remarkable value of 1.75 billion dollars.


Since I recently reviewed another pair of monoblock Class-D amplifiers, the AudioDinamica BeCube mono amp, about which you can read here – ITA only, and since ReMusic has already welcomed here the AGD Vivace’s world premier test, I won’t dwell on the technical considerations of the typology of these amplifiers. On this matter, I invite the reader who is interested in further exploring those aspects to check the articles mentioned above.

Going back to the AGD The Audion tested here, I must confess that I was really curious to listen to them, mostly for two reasons. First of all for the unusual choice of their engineer to enclose the power stage inside a bulb of a KT88 and to call them like the first thermionic valve ever documented, the one invented in 1906 by Lee De Forest: The Audion, precisely. Second, because I had recently reviewed the AudioDinamica and I was confident that I could detect differences, although subtle, between them.

To avoid any misunderstanding, other than this extravagant visual resemblance, these two tested devices don’t share any other characteristic with tube-based amplifiers.

Hence, should we take as false modesty this explanation given by its engineer Alberto Guerra about his unusual design choice? “Otherwise a class-D amp would just look like a box”. He simply declares.

What about the sound perception then? Where should our expectations stand? Might it be possible for us to find other unexpected resemblances exactly where we would not predict to find them? This is what we are about to try to discover. So, relax, serve yourself a drink, and keep reading.

AGD The Audion

Aesthetically, compared to their bigger brothers, the AGD The Audion mono-block, this pair of mono amps, has a more contained footprint and proportions that in some ways remind us of those of many head-phone tube-based amps. The contained dimensions and the not excessive weight are the characteristics of class D and T amplification. As I said on other occasions, I believe that those aspects constitute an important plus in devices with this kind of typology. With their 14 cm of width and about 19 of depth and height for only three kilos of weight each, the Audion allowed this editor to keep them on his desk next to his laptop used to write this review: how convenient! They also allowed him to easily connect them to anything that was handy during the time of their presence to his place.

Those who own amps, even the integrated ones, weighing tens of kilos, know very well how one becomes easily lazy and easily gives up experimenting with different pairings, just to avoid booking his chiropractor the day after.

The Audion shares with the Vivace a case entirely made in aluminum, this time in an unprecedented glossy version, mirror-like polished, instead of the matte version. On the 10 mm think frontal panel, fixed with four torx screws, stands out the brand name CNC engraved and stained in red, to match the logo printed on the GaNTube glass.

Except for the base dimensions, the Audion doesn’t have anything in common with the old Flying Mole. Do you remember them? Those were indeed anonymous little black boxes.

From the aesthetic point of view, the AGDs play in the major leagues. Resisting the temptation to enclose their content in that big, heavy, and useless chassis chosen by other designers, The Audion, instead, present an impressive showcase of their most precious and characterizing content. The visual appeal already present when the device is off, is simply astonishing when it is on, then a crown of amber-colored LEDs highlights the content, successfully mimicking the vacuum tubes aesthetic that inspired them.


Proceeding with the comparison with the vacuum tubes world, here we find on the upper side of the device, the cylindrical cage protecting the “valve” GaNTube, and the excellent WBT speakers binding posts. The owner’s fingers are safe, since it is obvious the GaNTube doesn’t produce any relevant heat, not even after hours of uninterrupted work.

On the back of the device, in the middle, we find a standard IEC power entry module – Medical Grade for EMI, safety and noise suppression – with a fuse holder that functions also as a voltage selector and its switch. On the sides, two inputs available both in standard XLR and RCA, and the selector switch.

The bottom of the device, a 5mm aluminum plaque, sits on four solid aluminum legs, equipped with O-rings functioning as vibration dampers. Overall the mechanical realization is of very high quality and conveys strength and elegance at the same time. It is a very successful choice, in my personal taste, the combination of polished aluminum and the dark-red color used to highlight the logo engraved on the front panel and printed on the GaNTube.

The provided power cables are very impressive, AGD products as well, of a good diameter and coated by a red and black sleeve perfectly matching the colors mentioned above.


The mood of those devices reveals, if we might say, a motorcycle spirit, and I’m sure I can rightfully predict that audiophiles that are also two-wheel enthusiasts, and in particular fans of the Milwaukee brand, will appreciate it.


A high-level order and an accurate assemblage reign inside. A particular attention has been dedicated to avoiding electromagnetic disturbance that can occur between the two overlapping PCBs, by separating them with a convenient metallic shield. A meticulously neat and of-first rate-quality wiring and audio-grade capacitors complete the picture.


As I said, the real biting heart of these electronics is encased inside the glass of a normal KT88 valve. This choice, very original indeed, was dictated by the marketing necessity of making the AGD Production immediately recognizable, but also to allow through a very peculiar Tube rolling a modification of certain characteristics such as the gain and power. About the latter, Alberto shared with me that a new 350-watt GaNTube will be shown possibly at Axpona 2020, this time enclosed in the bulb of the more spacious KT150. This is indeed what we call thinking outside the box!


AGD The Audion


When we are about to listen to a new device, every one of us is more or less unconsciously inclined to categorize it based on predetermined expectations. When those expectations are limited, we are often amazed by what we hear. Vice versa, if our expectations are high, we risk being disappointed. It is easier to speak than acting without biases.

It is a fact that the Class-D topology, has not yet all-out conquered the audiophiles’ hearts. Nonetheless, the devices tested here, in the most absolute terms don’t belong to the big group of products certain designers marketed by implementing tout court the over known Hypex, Icepower, Pascal, etc. modules. What we are handling today belongs to a more exclusive enclave of devices that, sharing the use of GaN semiconductors and certain design and engineering specifications, aim to overcome the limits and defects of that amplification topology. A sort of élite for which my expectations as a reviewer can only be really very high.

By my personal knowledge, today only a few designers benefit from the use of GaN: AGD, Merril Audio, Technics, Red Dragon Audio, Java HiFi. For all of them, we are talking about a sort of reference devices. Nowadays there are several companies that produce the required transistors: the first specimens made by International Rectifier date back to 2010, but, as usual, we expect in the future an increase in the offer and a subsequent price decrease, thanks also to the market entry of players of the level of Texas Instruments and Analog Devices.


Moreover, in less than ten years it has been already registered a considerable increase in GaN MOSFETs performances. If the first products could claim a switching speed double compering to the best MOSFET, by that time silicon-based, nowadays is considered common a ten times higher speed and more, which allowed to reduce and finally possibly completely eliminate the use of feedback, to the advantage of augmented dynamic and focalization.


Nonetheless, it is worth mentioning that many designers and engineers that haven’t joined yet this nouvelle vague, have not been sitting on their hands, but on the contrary have introduced new interesting products, like Hypex with the NC1200, utilized by Nord Acoustic, or the newborn Purifi by Bruno Putzeys, who proposes a new very interesting module containing all the know-how developed with the series NCore of Hypex.

The market of this typology of devices is still relatively young, and interesting innovations are waiting for us in the immediate future. Many brands already dedicated to the implementation of this typology of amplification are developing projects based on FET GaN, one for all NuPrime. Some companies have not yet moved in that direction because they are waiting for IcePower, Hypex, PowerSoft, Tripath, Sangway, etc. to make available their modules based on the GaN technology, to utilize them in their own products, to the complete advantage of the economy of scale.


AGD The Audion


And here we are now at the beginning of our musical journey, in the company of those fascinating amps.

For our test, we are going to use solid-state preamps and tube-based preamps, while as the source we are going to use as usual the CD player and streaming material.

The speakers are going to be monitors on stands but also speakers of major size. As I wrote, I had recently reviewed another pair of Class-D amps, so I referenced the same chart used before, to detect eventual differences between the two devices. Give me the time to retrieve my notes on previous audio sessions and I will be ready to begin with FKA Twigs and his LP1 to continue with Point by Cornelius.


The first characteristic that stands out in these unique electronic devices is their utterly high silence, the absolute absence of any residual electrical background noise is even more striking when compared with tube amps. This desirable characteristic highly contributes to emphasize the huge analytic capability and speed that The Audion are capable of.

The most impulsive sounds are reproduced with lightning-fast reflexes and equally rapid natural decay. The low-frequency control is unbeatable.

As I observed in previous listening experiences, the Class-D amplification allows a particularly generous use of volume, thanks in part to the high-level control of the low frequency of which they are capable. 

That’s also true when they are used to drive large diameter woofers. It is really surprising what they were capable of doing when dealing with “Morph the cat” by Donald Fagen. 

A very pleasant CD but characterized by low frequencies almost too invasive. With The Audion, the bass resulted perfectly controlled, deep, and visceral without ever staining the medium-high. This characteristic leaves intact tone and spatiality, while with other amplifiers, the only way to improve its listening would be lowering the volume.

In contrast with the AudioDinamica, with the AGDs it didn’t seem like the use of bigger woofers contributed to “warm-up” the tonality of these electronics. They, even with their tendency to “clearness” never seemed cold or poorly communicative, not even with LS50’s or the Fostex G1300MG’s small mid-woofers.

The power rendition always occurs without hesitation, no matter the dynamic content or the listening volume.

The speed – the declared slew-rate data were already per se very indicative – is always adequate, even when one listens to highly-dynamic pieces like some recordings of Cincinnati Pops Orchestra or the splendid live “At the Yoshi’s” by Dee Dee Bridgewater, where the metallic tweeters of the used monitors simply started to fly.

In short: a pair of amps that, borrowing the advertisement message of a famous energy drink, can put wings even on the most relaxed and lying-down audio system.

If it’s true that the appetite comes while eating, listening to pop and R&B energizing pieces I came across the only “defect” (is it truly a defect?) of these electronics. The Audion don’t like the “loudness” war. Moreover, they don’t like mixing with electronically altered voices and artificially augmented spaciousness.

In short and to say it all: they are a little snob!

Often, we write and read about electronics that badly digest less refined recordings. Well: these AGD electronics position themselves at the pick of my personal Hit Parade.

Perfect epigones of Dr. Jekill and Mr. Hyde, they are capable of sounding in a grand way with the best recordings of acoustic music resulting at the same time distasteful with much of the current mainstream production. With this latest type of recordings, even though I didn’t reach the barbarity to put in the lector a Californication by Red Hot Chili Peppers, the even overwhelming basses can still result controlled and the sound is not particularly boomy.

What is instead fastidious is the medium-high, which tend to become edgy to show in the worst recordings a distinctive acidity. The voices are mostly suffering, becoming nasal and showing hissing highs even in recordings in which we didn’t notice that problem before, maybe because of the speed limitation of the amps used. Therefore, is this behavior a real deficiency of the tested devices? A limitation in their use? It depends.

I underline that I don’t consider the mainstream music of a minor artistic value comparing to the cultivated music, jazz and symphonic. But it is a fact that it is very often quite badly recorded.

One can question if a high-quality device for audio reproduction should sound equally well with every type of music or if it could instead be designed to reproduce a specific musical gender at its best. I don’t know the correct answer, like I could not say who’s right between the Hi-Fi and the My-Fi supporters. What I can say is that personally, over an all-rounder behaving device I prefer the one that, even at the risk of strong characterization, is capable of excellence in some specific aspect.

In that sense, The Audion is among the more analytic amps that I’ve ever heard.

They are capable of reproducing details like and more than any valuable preamp, adding a strong characterization to the system in which they are included. If you were looking for electronics that sound magnificent in detail and timbrical accuracy capable of not lapsing into the coldness of an x-raying sound, and electronics fast enough to reproduce any dynamic excursion, would you accept the fact that it could make a mediocre or bad recording sounds not “acceptable” anymore ? I would.

I would never choose a device that, to make any musical content acceptable, even what was badly recorded, might introduce a sort of equalization by subtraction from the original musical content. One has to understand the meaning of “Garbage in... Garbage out!”

The Audion is like a breed sports car: in addition to enthusiastic performances, you cannot ask it to provide the comfort of a spacious SUV.

It is true: every subtle imperfection of the road surface will transfer to the steering wheel. But do you consider the steering precision and the intoxicating sensation of total control that a vehicle of that sort can give you?

Feed it with valuable recordings and I’m ready to bet that you will have to quickly accept to reconsider all your predetermined positions about Class-D topology.

At the cost of repeating myself, what I want to underline is that, besides owning well-recorded material, it doesn’t matter here if you are a vinyl or a digital purist, but if like me you love to alternate different electronics according to the musical genre you are listening to or according to your mood, be aware that these AGD amps position themselves within the league of very high if not into the highest level of electronic amplification one can use.

Their sound is extremely rich and detailed, textured by an almost infinite number of nuances. The dynamic performances and the undistorted volumes of which they are capable can satisfy any audiophile, including the one who sometimes likes to blow up the window glasses of his living room!

All this richness of information is accompanied by a truly excellent tonal balance. The spatial representation is generally good or very good, mostly in the width of the sound stage. Regarding the deepness and the wrapping feeling, some Tube Amps may still have some ammunition of their own to match The Audion, euphonic ammunition, of course…


To whom would we recommend those electronics?

First of all, to fans of jazz music but also to those who prefer chamber music and in general to those who privilege the acoustics.

Personally, I very much appreciated them also with the electronics of Brian Eno, Ryuichi Sakamoto, Alva Noto, Cornelius and with the repeating and minimalistic music, rich in tonal variations of Philip Glass and Ravi Shankar.

Independently from the listened musical genre, I would recommend them to people willing to explore the Class-D topology and who, already owning other state-of-the-art Tube or solid-state amps, is looking for a product undoubtedly comparable to those they already own.

Because of their sonic qualities of absolute value, their accurate mechanical construction and their precious material, and at the same time because of their unique design that allows a peculiar and easy upgrade through tube rolling, my FI* for these AGD The Audion is a four.


*The Farewell index FI expresses how painful it is for the reviewer to detach from the tested devices when it is time to return them. The values or this system goes from a minimum of 0 of “no regret” to a maximum of 5 “if I can afford it, I buy it!”.




FKA Twigs - LP1 - Young Turk Recordings 889030011824

Cornelius - Point - Polystar Japan B01KAS00JC

Cornelius - Mellow Waves - Warner Music Japan WPJL-10106

Bjork - Vespertine - Polidor 589000-2

Donald Fagen - Morph The Cat - Reprise Records 9362-49975-2

Dee Dee Bridgewater - Live At Yoshi’s - Verve Records 7773

Cincinnati Pops Orchestra - Star Tracks - Telarc CD-80084

Alva Noto – Unieqav - Noton PDIP-6576

FSOL - ISDN - Virgin 7243 8 40387 2 4

Philip Glass - Einstein On The Beach - Elektra 7559-7935-9

Ravi Shankar - Passages - Sony Classical CD23

AIR - 10.000 Hz Legend - Virgin 7243 8 10332 2 7

Burial - Burial - Hyperdub HDBCD001

Sakamoto - Chasm - Warner Music Japan WPCL-10072

Sakamoto - Plankton - Milan CD 399 846-2

Quincy Jones - Ultimate Collection - A&M Records 583 565-2

Chiara Civello - Canzoni - Sony Music 88843063812

Rachelle Ferrell - First Instrument - Blue Note 72438 27820 2 5

Petra Magoni - Musica Nuda - Radio Fandango 0171232RAF

Roberta Gambarini - So In Love - Groovin' High 060251 7960107

Lucia Minetti - Jazz Nature - Velut Luna - CVLD 294

Joss Stone - The Soul Session - Virgin 00602557280036

Melody Gardot - My One And Only Thrill - Verve Records 1796781

Ben Harper - Diamonds In The Inside - Virgin 7243 5 82502 2 0

Stereolab - Cobra And Phases Group Play Voltage In The Milky Night - Warp Records D23R

I Am Kloot - I Am Kloot - Music On CD MOCCD13795



Specifics declared by the designer

Output power: 85W 0,01% THD+N, 20Hz÷20kHz, 8ohm

Total harmonic distortion THD+N: <0,005% 10W/1KHz

Max output power: 170W 0,1% THD+N, 1kHz, 4ohm

Bandwidth: 5Hz÷100kHz ±3dB

Input impedance: 40kOhm, 600ohm, custom request

Efficiency: >94%

Range signal/noise: <-130dB weighted A

Frequency PWM: 400kHz

Dimensions: 140x191x191mm WxHxD

Weight: 2,3kg/5.1lbs

Voltage: 110-240V manual user selectable

Official distribution: direct sale, to AGD Production website

Price at the review date: 6,800.00 EUR satin version pair, the object of this test, and 7,500.00 EUR for the SE - Special Edition polished version

Used system: to Paolo Mariani’s system ITA only

by Paolo
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