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Esoteric i-03


This review first appeared in the August 2011 issue of hi-end hifi magazine of Germany. You can also read this review of the Esoteric I-03 in its original German version. We publish its English translation in a mutual syndication arrangement with the publishers. As is customary for our own reviews, the writer's signature at review's end shows an e-mail address should you have questions or wish to send feedback. All images contained in this review are the property of fairaudio or Esoteric - Ed.

Fat D! The Teac/Esoteric word combo surely elicits instant visions of tank-like CD players. And that’s very factual. It’s what the Japanese are best known for and continue to offer. For top crop machines, even competitors go to the Esoteric well for the legendary VRDS sleds. Think Paganini transport by dCS, Playback Design or Audioaéro’s luxury deck La Source. To each case belongs a sticker Esoteric inside. But clearly no insider knowledge is needed to predict an uncertain future for any firm that would specialize solely in expensive to ultra-expensive SACD/CD players.

Years ago Esoteric thus already branched out into various D/A converters, then became a complete front-to-back provider with electronics, loudspeakers and cables. The current catalogue includes two stereo power amps, a pair of class A/B monos, a preamp, a phono stage and today’s contender, the Esoteric I-03 integrated amp which combines the C-03 preamp stage with new class D power modules designed especially for this machine.

Esoteric I-03_01

Contrary to the previously reviewed AI-10 as the firm’s first class D effort and sadly discontinued since, the new I-03 positions itself in an area usually reserved for mature pre/power separates. But ‘usually’ is perhaps a bit old-fashioned given that expensive super-ambitious integrateds no longer are as rare as they were perhaps 10 or 20 years ago. Clearly Esoteric’s latest is an unapologetic luxury attempt. That makes the design team twice as courageous for embracing class D power which many listeners still view with barely disguised suspicion. I frankly find such reactions peculiar.

True, clichéd warfare between various religious factions committed to favored solutions—analog vs. digital, tube vs. transistors, evil vs. benign feedback—has been endemic to the high-end for seemingly ever. It’s no surprise that class D amplification should be exposed to serious disagreements about its worthiness too. Beyond argument is simply the far higher efficiency of such circuits. Whilst traditional class A/AB architectures throw away 50% to 80% of consumed wall power as heat, switching amplifiers reduce the same wastefulness to between 10% and 20%. The upshot is obvious. Equal output power becomes possible with far smaller power supplies. Likewise for seriously scaled back cooling solutions. These two items reflect directly in cost savings for both manufacturing and shipping relative to size and weight. The price advantages of lower weight at least theoretically also suggest higher value. So much for theory and class D. Then the Esoteric I-03 arrived. On a euro pallet.

Esoteric I-03_02

Apparently the Japanese got confused over the concept. The amp’s packing alone weighs close to 10kg, i.e. noticeably more than the pair of NuForce class D monos we reviewed in 2008. The amp itself weighs 31kg. What gives? The outer casing is a first indicator by practicing not merely Scandinavian design restraint and superlative finish but material generosity. The fascia is thick as a fat thumb though the elegant bevels do minimize the visual impact. The rounded front corner pieces further undermine cosmetic boxiness but add mass. Ditto the 5mm base and 7mm cheeks which double as heat sinks. Likewise for the 5mm cover with the brand's engraving. The I-03’s enclosure is truly massive. Popping the bonnet adds more reasons for the weight. Thankfully I earlier only said class D power supplies may be smaller. They clearly needn’t be.

The innards here are subdivided into five chambers for specific functions. The Japanese explain that the layout is highly deliberate to reduce mutual interference between building blocks whilst shortening the signal path. The two preamp boards—a 2mm steel plate separates the channels—thus mount directly to the rear panel since that’s where the inputs live. Except for the single power transformer, the I-03’s circuit is built up fully dual mono.

Esoteric I-03_03

The central and massive transformer behind the fascia resides on its own steel plinth to channel possible mechanical vibrations effectively into the bottom panel and from there into the patented footers to combat microphony. The casing surrounding the trafo blocks stray fields from intruding into surrounding circuitry. Integrated into the baffle with its own fully enclosed metal sleeve is the dimmable/extinguishable display and overall steering logic circuitry. The power supply for this module is shielded as well to eliminate microprocessor noise from intruding into the amplification path. The two lateral bays contain the class D output stages which are mounted vertically for maximal thermal conduction into the beefy chassis cheeks.

Channel separation, noise suppression and signal path shortening rely not merely on clever layout, mechanical separation and shielding says Esoteric. There's also the elimination of a conventional stereo potentiometer. Instead each preamp board gets its own IC with integral resistor network to adjust amplification factor directly.

Esoteric I-03_04

This eliminates HF distortion and a long cable detour from board to pot and back. The audio signal leaves the preamp boards only once – directly to the output stage.

Esoteric I-03_05 Here an International Rectifier chip modulates the signal into a ca. 800kHz square wave whose variable-width on/off pulses trigger six Mosfets (three per push/pull phase) from the same supplier. Post low-pass filtering to eliminate the carrier frequency—which would otherwise have the machine broadcast—the now amplified music signal appears at the speaker terminals.

Back to power supply and weight, the question becomes why no SMPS? The Japanese clearly reverted to a conventional power transformer and not even a toroid but a less efficient EI core. The first reply was brevity itself. "Because we like it." Perfectly adequate!

The longer reply explained that experiments with various switch-mode power supplies resulted in noticeably higher output power but inferior sonics, hence the usual ‘analog’ power supply. Ditto for no toroid. Though somewhat ‘slower’ than equivalent donuts, the EI was smoother and more pleasantly three-dimensional which in conjunction with the class D signature sound created the most desirable balance of attributes.

Finally a four-cornered enclosure section gets more effectively occupied by a four-cornered than round transformer. More effective use of space equates to a larger more powerful core with obvious sonic benefits. The 10kg iron block here manages 940VA.

Though the minimalist fascia wouldn’t let on, the I-03 is massively functional. There’s nothing lacking. Just don’t misplace the remote or 90% of the functions will go bye-bye. There are 3 x RCA and 2 x XLR inputs. RCA 3 can be converted to MM or MC phono (47kΩ or 100Ω impedance).

RCA 2 can be converted to direct/thru whilst bypassing the preamp stage (particularly practical for AV system integration). The pre-amplified signal can be tapped via the single pair of pre-outs three different ways – ON1 retains the power stage for biamping for example; ON2 deactivates the power stage to convert the I-03 into a pure preamp; REC presents the unattenuated signal.

What else can the machine do? Inputs may be named and input sensitivities assigned to equalize source voltage differentials. There’s balance control without additional circuitry since volume control is dual mono. This works discretely for each input. A propos volume, there are five preset tapers to customize how fast or slow volume ramps up. Things can go louder slowly first, then faster – or vice versa. How did one ever live without this?

More important perhaps is the headphone socket and that the power switch lives on the front. No more crawling behind the rack to grope for the mains switch. What innovation! The only salty crocodile tear will be shed by biwiring freaks who only get one pair of speaker terminals per channel.

The Esoteric I-03 was one of those components which cause me concentration issues. I had a tough time extricating individual sonic traits analytically. "Nothing is missing, nothing attracts attention or disturbs" …was my spontaneous first reaction… "what else to say?" It’s of course very praiseworthy when a machine leads one directly to unselfconscious listening rather than subliminal references against an internal sound check list. But for a reviewer chasing clear personality traits, it’s actually more of a pain.

Esoteric I-03_06

Dual-mono preamplification boards separated by steel barrier

So let’s start by calling the Esoteric an all’rounder rather than eccentric. This means maturity and balance without any aural bling or kinks. The same goes for tonal balance. Except here I wouldn’t go as far as calling it dead neutral since minor tendencies remain. To cross things off the list, I’ll begin in the bassment. For an amp of its sticker and kind this band conforms with expectations of power and reach. Bass is substantial, extended and neither bone dry nor buttery soft. Semi sec seems most appropriate. Unlike certain amps like the Gryphon Atilla, bass here doesn’t attract attention. This merits asking why. The Dane’s upper bass has a small emphasis which renders the Esoteric the more neutral by comparison in this area. This also means that the Atilla’s particular punch and fun factor don’t translate fully to the Japanese. The low bass of the Esoteric is finer and what’s perceived as better will depend on the listener.

Esoteric I-03_CD1 Way down low the Esoteric is alive and twitching but gnarly records also make clear that more remains possible versus my usual combo of Octave tube preamp and Electrocompaniet monos. ‘More’ refers less to sheer quantity (though that factored a bit) but mostly to stability and articulation. Take the very very unusual woodwind fare of extreme sax player Colin Stetson—check out this Youtube video for a taste—on New History Warfare Vol. 2, Judges. On the number "All the Days I’ve Missed You" the infrasonic blubber of the French horns had firmer consistency with my pre/power duo and the inner structure of those noises was keener. Whether that’s any necessity is a different matter of course and that combo costs 30% more too. That it puts out more foundation energy is not entirely surprising.
Esoteric I-03_07

One channel's class D output stage

Though more potent in the mid and upper bass, the Gryphon’s low bass was actually a tad lighter than the Esoteric’s. These descriptions are graduated hues and nothing earthshaking. In matters of infrasonics I’d rate the Esoteric as falling between the Dane and my German/Norwegian combo. Even so the Esoteric doesn’t produce ‘impressive’ bass like a big cruiser boat's bow wave. The lower registers simply act as seamless extension of the midband. And the midband is where the I-03 gets specific. But first the treble.

Here the same impressions/descriptions of the bass factor – flawless continuation of the vocal band without diva-esque attention grabs. I heard neither harshness, dirt nor extra sparks. Some amps draw out (or create?) more scintillating air particularly around brass and woodwinds. Here the Gryphon was cut from the same cloth. Neither amp directs the listener to pay specific attention to the upper frequencies. They simply exist and if in doubt register more on the milder side.
Esoteric I-03_08

960VA EI core power transformer

Esoteric I-03_CD2 The Esoteric goes on the charm offensive with the midrange. Here Tori Amos’ "Blood Roses" became perfect example particularly vis-à-vis my separates. Those handle this band decidely different. My initial quickie assessment was that the I-03 was warmer, the combo fresher. The cembalo string attacks were harder, more incisive, direct and steely over the duo; fleshier, fuller and softer with the integrated. This applied to the voice too. It seemed 3° to 4°C warmer than usual. This was accompanied by somewhat larger scale as though the voice had grown to occupy more space whilst outlines were somewhat less tacit or defined. I wouldn’t go as far as invoke a bath of golden light the Esoteric dips everything into but a core tendency toward bronze rather than silver is applicable – a very fetching nearly elegant hue that’s decidedly not the coldly analytical blue-white fluorescent lighting of strip malls.

Esoteric I-03_CD3 Whilst the midband of the I-03 was gentler, the decisive difference to me appeared in the presence region. Two minutes into the song and lassie Amos begins to scream. At stout levels over my standard setup this equates to ear ringing. It’s painful. Not so the Esoteric. No worries, the lady still protesteth in earnest but up high she does so a bit milder, less incisive and penetrating. Asked to decide between ruthlessly honest or conciliatory, the Esoteric I-03 goes for diplomacy. That’s easily confirmed with harsh e-guitar riffs or power piano. The Japanese is a mellower operator. Occasionally this undermines the hard honest just-so approach a bit. But relative to long-term friendliness and lean-ish forward mastered fare it’s quite the boon. Contrary to my reference separates, I can’t imagine a system or musical choice where the Esoteric would ever go on anyone’s nerves.

Esoteric I-03_09

Granted, if you prefer your mids wiry, lean and tacitly present, you may not – um, warm to the I-03. Its approach is mellower and softer. Or "clearly superior" as colleague Jörg opined with Miles Davis’ "My Funny Valentine" after I switched him from my stuff to the Japanese. The trumpet was "warmer, most pleasant, somehow more organic or natural". Yep, one clearly could see it that way.


Esoteric’s I-03 is a very complete integrated amplifier that's free from sonic gaps or dominant voicing. While this doesn’t eliminate character, it’s first and foremost an all’rounder which convinces with its breadth of sonic virtues rather than specific highlights. Only on second listen do certain micro tendencies present themselves. The design team does prefer silky fluidity to dry rhythmic élan. The tonal balance is a few degrees warmer than dead zero and the overall milieu is one of integration, not 100% neutral separation down to the molecular level.

Esoteric I-03_10

This machine is well balanced and satisfying. I recommend a longer audition than a quick A/B or a few short test tracks. Think long-distance runner. Virtues don’t communicate after 100 meter sprints. Those could easily lead to misjudgment. Best indeed would be a weekend loan if the dealer is amenable, then sampling the widest variety of music.

Psych profile

  • Tonally neutral bass with sufficient reserves for current-hungry transducers. The quality is semi dry with good balance between articulation and fleshiness. Perfect integration with the midband. Some of the competition offers more punch and speed.
  • The treble is clean, free of artefacts and arguably at home on the milder side of the fence though ‘rounded over’ already overstates it. Seamless integration with the vocal range.
  • The midrange is pleasantly juicy and sonorous. The lower midrange-to-presence- region transition is somewhat subdued for a slight softening effect. Many recordings benefit. Simultaneously transient acuity mellows.
  • The virtual stage shows ample breadth and depth in line with the price. Instruments and vocals are dimensioned generously. Localization sharpness is spot on.
  • Good timing and dynamic chops but by tendency the Esoteric subscribes more to musical flow than toe-tapping fanaticism.

Esoteric I-03_11


  • Dimensions and weight: 445 x 162 x 468mm (WxHxD), 31kg
  • Trim: Clear-anodized silver
  • Socketry: 3 x RCA, 2 x XLR in (one RCA convertible to MM or MC phono, 1 x RCA out, 1 pair of speaker terminals per channel
  • Output power: 240/360wpc into 6Ω RMS/peak
  • Other: Fixed-gain thru-put, headphone output, defeatable output stage for pure preamp use, assignable input sensitivity per input, remote control, dimmable/extinguishable display
  • Power consumption: 45 watts at idle, no standby
  • Warranty: 2 years

Article written by Ralph Werner

Reference System

  • Sources: Analog - VPI Scout II, SME M2 12-inch, VPI JMW 9T, Denon DL-103, Ortofon MC Rondo Bronce,
    Zu Audio DL-103, SAC Gamma Sym – digital - Luxman D-05, Logitech Squeezebox 3, Readynas Duo NAS-Server,
    HP Notebook, Benchmark DAC1 USB
  • Preamplifier: Octave HP300 with MC phono
  • Power amplifier: Electrocompaniet AW180
  • Integrated amp: Denon PMA-2010AE
  • Loudspeakers: Ascendo System F, Thiel SCS4
  • Various accessories, cables and racks
  • Review component retail: €9.499.

Source: 6moons

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