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Reviewer: Frederic Beudot
Financial Interests: click here

Digital Source: Esoteric X-03SE, Weiss Minerva [on loan]
Analog Source: Acoustic Solid Classic Wood, AS WTB211, Grado Reference Sonata 1, Denon DL103, Clearaudio Nano, Audia Flight FL Phono (on loan), ASR Mini-Basis Exclusive [on loan], Esoteric E03 [in for review], SQ-PH-1t [on loan]
Pre-amplifier: Esoteric C03 (on loan), Wyred 4 Sound STP
Amplifier: Genesis Reference 360, McIntosh MA2275
Speakers: FJ OMs, Rogers LS 3/5a, Zu Essence
Cables: Zu Varial, Zu Libtec, Esoteric Mexcel 7N-DA2100 Balanced interconnects [on loan]
Power Cords: Zu Mother, Isotek Power, ACCUSTIC ARTS Ferrite II [on loan]
Powerline conditioning: Monster Power HTS5100mkII, Isotek Nova and Titan [on loan]
Sundry accessories: Isolpads under electronics, ASI resonators and sugar cubes
Room size: 12’x13.5’x8’
Review component retail: $12,000

If you had asked me for the skinny on Esoteric five years ago, I’d have told you about a Japanese company that is one of the strongest supporters of SACD, builds the best digital transports in the world but sometimes struggles to take full advantage of their technological lead because of output stages which are not quite up to the same standard as the rest of their designs. Esoteric may not fully agree with this curt assessment but I doubt people familiar with the brand would call me far off the mark.

Although Esoteric still builds the best digital transports today and still champions SACD, they have become far more than that. They now are a full-range audio company tackling state of the art components in every category they enter. I finally heard the SA50 and concur with Srajan that Esoteric has significantly lowered the price of admission for superior SACD playback while adding a variable output and USB support at no cost (although not high-resolution USB which damped my enthusiasm somewhat). No introductions are needed either for the C03 preamplifier which earned a double Blue Moon award from Srajan and me; or the tube A100 integrated/power amplifier which has collected awards around the world; or even the more controversial MG10 and MG20 speakers with their vanishingly low distortion and similarly low tonal density.

Esoteric is slowly but patiently expanding into all the segments of the audio market with new solutions, technologies and ideas wherever they go. The E03 phono stage in house for review will be another earthquake which, I believe, shall redefine what can be expected in a category at a given price point - but that’s a review for another day.

Given these precedents, I was both interested in what Esoteric would do in the department of solid-state amplification with the long awaited A-03 power amplifier but also surprised to see them author a far from novel and no longer so politically correct pure class A design. Let’s get this handled upfront then. From an environmental and energy consumption standpoint, pure class A amplifiers are an aberration - but they usually sound very good. I am not here to tell you what’s right nor what you should or should not do. I am here to tell you that 400 watts of idle power draw—to deliver just 50 watts into 8 ohms and more likely a fraction of one watt 99% of the time—is highly inefficient. It does come with this territory. Whether you should care or not is your decision to make. Before you ask, I do use a class D amplifier as reference because I love how it sounds. Its higher energy efficiency is a nice fringe benefit but was not the determinant in my choice.

In an effort to minimize power draw, the A-03 offers a 'warm-up mode' that keeps the components critical to best performance at operating temperature when it only uses 220 watts. When playing music, the A-03 turns into a sizeable space heater, never too hot to touch but radiating significant heat nonetheless. I received the A-03 in August when this aspect was less than enjoyable yet a few weeks later when the weather had turned rainy and cool, the A-03’s thermal behavior was a lot more welcome.  From its circuit conception, the A-03 is rather conventional. There aren’t that many different ways to build a class A output stage.

What is not conventional is hidden amongst the details, in the meticulous attention to implementation that is typical of the brand. The power section parallels five push-pull transistors per side (ten transistors per channel) all biased in pure class A and jointly capable of delivering RMS output power of 100 watts into 4 ohms and 50 into 8. Each of the five transistor pairs per side has sustained current capability of 17A and peak burst headroom to 34A. With each A-03 amplifier running 10 pairs (20 transistors), that makes for rather bottomless current delivery. As a double-mono concept, the A-03 features independent toroidal transformers for each channel, mounted to the side of the amplifier. The voltage stage feeding the current stage also relies on an independent transformer for optimal stability and responsiveness. In typical Esoteric fashion (see the C-03 or P-03/D-03 reviews), each section of the amplifier enjoys its own internal enclosure for both mechanical integrity and reduced interference. Parts and components are of the highest grade available, the most readily visible being the 5-way WBT NextGen binding posts which accepted large and small spades as well as banana plugs without issue.

The back of the amplifier offers both RCA and XLR inputs although the design is single-ended similarly to the C-03 because Esoteric’s engineers determined that single-ended operation both sounded better and was quieter than balanced. I have a lot of respect for a design team that picks the mode of operation they think works best from component by component rather than push marketing hype that claims balanced is always superior. The input format is selected via switch in the upper right corner and a second lower switch allows bridging both channels to convert the A-03 into a 200-watt at 8ohm monoblock. Although not tested in this configuration, I can only imagine that the 170-amp current capacity would resolutely drive absolutely any speaker regardless of how abysmal their impedance curve may look.

The design cues match the other 03 Series components flawlessly with the beveled fascia, brushed aluminum plates and engraved Esoteric logo yet nothing screams “Esoteric 03” louder than trying to lift the beast. Regardless of how many of those Japanese components have come through my listening room, I am never prepared for the sheer density of Esoteric’s finest. At 38kg or 80lbs, the A-03 is no different. Do not try and lift it alone.