Esoteric I-03When it comes to amps, my beat here at the SoundStage! Network involves integrated amplifiers, which for the most part have been solid-state. The one exception has been the Esoteric A-100, which I reviewed in 2008. Reviewing that $19,000 USD amp based on the KT88 output tube was a singular experience -- it remains one of the finest amps I’ve ever heard. So I was intrigued when Jeff Fritz offered me the opportunity to experience what Esoteric could do in a lower-priced but higher-powered solid-state integrated amp, the I-03 ($13,000). I leapt at the chance.

Esoteric’s parent corporation is TEAC, founded in 1953 and long a maker of consumer and pro-audio electronics sold under the TEAC and TASCAM brands. Esoteric is the company’s high-end division, in which TEAC fuses the best of design, technology, engineering, and manufacturing. Esoteric’s current model roster includes full lines of preamplifiers, amplifiers, and digital components, all conceived, designed, engineered, and built in Japan.

The I-03 is part of Esoteric’s Master Sound Works (MSW) series, which began with the A-100. As TEAC’s North American representative put it, Esoteric takes their MSW project "very seriously." When Esoteric targets a product category and a price point, their goal is to use new technology and/or new designs to do a better job than their competitor(s). If they feel they can’t do a better job, they don’t take on the project. According to TEAC, Esoteric is all about evolving audio technology to the next level. I rejoice in knowing that Esoteric is driven by true two-channel audiophiles.

Specifications and design

The I-03 is Esoteric’s flagship solid-state integrated amplifier, and is based on the award-winning C-03 preamplifier and on technology they’ve developed in their 50+ years of designing amplifiers. The I-03’s preamplifier section has a dual-mono architecture: each channel’s circuitry is on its own completely independent board, separated by 2mm-thick steel plates to eliminate any potential for cross-channel distortion.

The amplifier section is the MSW pure-class-D power amplifier used in Esoteric’s other class-D amps, and has high-speed MOSFET devices in a parallel push-pull configuration. The power-amp blocks are also in dual-mono architecture, with separate power-supply sections for each channel; this is claimed to achieve superior speaker drive performance. The I-03’s powerful analog power circuits are configured using large capacitors and high-capacity custom transformers, to produce a distinctive sound that Esoteric claims is both robust and smooth.

The volume control is based on what Esoteric calls its Dual-mono Volume Control (DVC): A rotating knob transmits signals to the I-03’s two preamp sections, and simultaneously drives both volume-control amplifiers. This is done to maintain the separation of the left and right audio signals, to achieve exceptional channel separation. There is no audio-signal wiring between the audio board and the Volume knob, to shorten the signal path and prevent further deterioration of the sound.

The I-03 can also function as a standalone preamp, and for that purpose is equipped with a power-amplifier shutdown function.

All in all, a lot of original thinking backed by solid engineering.

Compared to the tubed A-100, the I-03 is a powerhouse. Delivering a muscular 180Wpc into 8 ohms -- or 240Wpc into 6 ohms or 300Wpc into 4 ohms -- the I-03 should have no trouble driving most speakers. Its total harmonic distortion (THD) is said to be <0.003%. The frequency response is specified at 5Hz-70kHz, and the claimed signal/noise ratio is >110dB.

Esoteric I-03

The I-03 is handsome and contemporary in appearance, with a sculpted front panel that mimics those of other Esoteric models. It looks very solid, with brushed-aluminum panels -- and with dimensions of 17.5"W x 6.4"H x 18.4"D and a weight of 68 pounds, it looks and feels very substantial.

The top panel is bare except for the Esoteric logo, which is engraved toward the front. The bottom panel has three substantial, self-leveling feet. The front panel has a large, centrally placed, blue fluorescent display flanked by two large knobs: input selection on the left, Volume on the right. With the substantial remote control (included) the user can not only adjust or select volume, mute, input, and display brightness, but also operate Esoteric’s digital music and video players. To the right of the display is a 1/4" headphone jack.

The rear panel is flanked on both sides by plastic-shrouded five-way binding posts. From left to right in the center of this panel are: two pairs of XLR inputs, two pairs of RCA inputs, one RCA MC/MM phono input, a signal ground, and one RCA preamp output. Just below these last three is the IEC receptacle for the detachable power cord -- which I ditched in favor of Cardas Audio’s Cross power cord, which normally connects my Jeff Rowland Design Group Concentra integrated amplifier ($5600 when available) to my power conditioner.

The only setup problem I had was in connecting my speaker cables to the I-03’s binding posts. Because the spade lugs of my Cardas Neutral Reference cables are so narrow, I couldn’t secure them to the post in the usual fashion; i.e., with the post in the center of the lug. However, since the I-03’s posts are drilled out in the center to accept bare wire, I was able to insert one arm of the lug in that space, then torque down the nut for a firm grip.

Setting up and burning in

The I-03 was shipped to me in a substantial cardboard box nested inside another substantial cardboard box. Although heavy and lacking rack handles, the I-03 was relatively easy to uncrate; I was able to get it up onto my equipment rack with no difficulty. Setup time was less than ten minutes; I used the XLR inputs exclusively.

The review sample had been sent straight from the factory, and I’d been told that it would require a few hundred hours of break-in time. That was confirmed by my listening. For the first few weeks the I-03 sounded uninvolving, very cold and sterile. Gradually this quality faded, but I was impatient and wanted to get started. I’m generally wary of tweaks, but having heard and read a lot about Cardas and Ayre Acoustics’ Irrational, But Efficacious! burn-in CD, I used it to hurry things along. Now, as a medical doctor, I’m very aware of placebo effects. Yet while I’m not willing to bet money on it or to perform any A/B comparisons, I felt there was an improvement, with a softening of a harsh, edgy quality and an overall warming of the sound. My buddy Max declared that there was no question that the Irrational, But Efficacious! CD improved the sound -- not only of the I-03 in my system, but of his own home system as well. Your results may vary. Regardless, thereafter, for the duration of the review, I heard no further change in the sonic character of the I-03.


Once the I-03 was fully broken in, its strengths became readily apparent to me. My first thought was I’m going to be listening to a lot of classical music with this amp, and that’s just what happened. The I-03 wasn’t the quietest amp I’ve had in my system -- there was some hiss at high volumes with no music playing -- but this wasn’t noticeable at normal listening levels, nor was it ever audible while music was playing, even during the quietest passages. Indeed, the I-03 was commendably transparent, with "black" backgrounds and a broad, deep soundstage that favored the reproduction of recordings of acoustic music -- particularly symphonic music. The ambience of the venue, the natural reverb and decay of the hall -- its sonic signature, if you will -- was nothing short of outstanding, regardless of the recording. The I-03 was detailed in a good way, without overemphasizing the treble. As a result, there was less of an emphasis on leading edges, which ensured a smooth sound. Lest you think this made the I-03 sound warm and gauzy, that was far from what I heard: The I-03 was quite neutral, even somewhat on the cool side. One notable effect was that the imaging and soundstaging sounded more open and natural. The tradeoff was that the imaging was less three-dimensional -- but I’ve found that I prefer this with large-scale acoustical music, particularly classical works.

Right around the tenth anniversary of 9/11, while driving to work, I heard on the radio a performance of Gustav Mahler’s Symphony No.2, "Resurrection." I was so blown away that, when I got home that evening, I purchased and downloaded the San Francisco Symphony’s recording of the work, conducted by Michael Tilson Thomas (24/96 AIFF, SFS Media/HDtracks). I’ve been listening to it regularly since then, and its combination of instrumental and vocal elements made it the perfect recording to help dissect the I-03’s capabilities.

From the opening notes, the I-03 was able to convey both the grace and intensity of this performance, laying out the music as it swings with emotional intensity from melancholy to blossoming hope. The I-03 was nimble, exhibiting both delicacy and a firm grip on the music and allowing for its graceful ebb and flow, yet with tight control and dynamic impact when called for. The strings had substantial bite, and a smooth, warm tone that floated gracefully over the soundscape with airy delicacy. Yet when the brass kicked in and the tempo abruptly changed, the I-03 was able to deliver the forceful impact of the climax, then ease back again into the strings with no difficulty. Even during intense passages with forceful crescendos, the I-03 held the performance together, clearly lending weight to the underlying cellos without compromising the dynamic impact of the brass.

Although the chorus in the final movement was a bit too recessed for my taste and quite low in level, this is a feature of the recording and not any weakness of the I-03. However, when soprano Isabel Bayrakdarian and mezzo-soprano Lorraine Hunt Lieberson performed their solos, their voices had the proper perspective, with every inflection and coloration accurately conveyed and all their emotional intensity preserved.

Although the I-03 reveled in reproducing acoustic performances, it was no slouch with amplified music. Having long been a fan of Steve Vai and Joe Satriani, I’ve been listening to a lot of their recordings lately, particularly the live G3 albums with Eric Johnson. In these days of overly compressed pop and rock recordings, listener fatigue can set in pretty quickly. With the I-03 this was not the case, largely due to its softening of the leading edges of the treble, mentioned earlier. On G3’s Live in Tokyo (16/44.1 AIFF, Sony Music), lead runs by the three featured guitarists had the proper attack and edge without sounding harsh; I was able to listen loud and long without bleeding ears.

Immediately after hearing electric bassist Dean Peer perform at the T.H.E. Show in Newport last June, I bought his Ucross (CD, Restless 9101) from a vendor there. Since then it’s been in heavy rotation, and I’ve found it very useful for evaluating the bass performance of the components I review (see my recent Ultra Audio review of the PBN Audio Montana InnerChoic Liberty loudspeaker). Since that time I’ve also purchased Peer’s Airborne (24/96 AIFF, ILS/Cardas Audio), which features his electric bass paired with a drummer, just as he’d performed at T.H.E. Show. The I-03 delivered liquid bass with solid weight and resonance. Bass definition was very good, but a touch less taut and less warm than I prefer. Despite this finding, it was never less than enjoyable, and wasn’t something that would capture my attention for long.

Though I primarily listened to the I-03 driving my Wilson Audio Sophias, I also listened with my Sennheiser HD 600 headphones plugged into the Esoteric’s headphone jack. The I-03 was able to drive the HD 600s quite well; the sonic similarity between the HD 600s and the Sophias confirmed the impression of the I-03 that I’d gotten while listening through the speakers.


The Esoteric I-03 and my current reference integrated could not have sounded more different. The I-03 had a consistently wider, deeper soundstage than my Jeff Rowland Concentra, and in this parameter was among the best I’ve heard in my current room, ranking up there with the ASR Emitter I ($10,950). This quality was especially noticeable with large-scale symphonic music, and was reflected in the choice of music that I tended to listen to during the audition period. And while I felt that the Concentra imaged better than the I-03, the fact that the I-03’s sound was more open and diffuse made it clearly superior to the Concentra with this type of music.

However, the I-03 was consistently cooler in tone than the Concentra, and while this favored classical recordings, it could a bit too cool for other genres, particularly jazz and rock.

Bass-wise, the gold standard for me is the Luxman L-509u ($10,000). While the Concentra was clearly beaten by that amp, I felt that not only did the Concentra sound warmer than the I-03, it had a better grip on the woofers of my Wilson Audio Sophias, with better definition.

How did the I-03 stack up against its corporate sibling, the A-100? I can’t really make that judgment. Not only has too much time elapsed since that review, but the A-100 was reviewed in a much smaller and sonically compromised listening room, and with a different digital front end. Additionally, the technologies used in the two models are so radically different that, barring a head-to-head comparison, any speculation would be pure conjecture and unfair to both amps.


Esoteric’s Master Sound Works I-03 is a solid performer with excellent build quality and ergonomics and enough power to drive all but the most power-hungry speakers. It does many things very well and has no glaring weaknesses.

The funny thing is that I didn’t know much about the technology used in the I-03 during the listening period. Only when I read the specs while completing this review did I learn, to my surprise, that the I-03 is a class-D amp. Is that why I found it to be on the cooler side, or is that the sonic signature that would have been designed into it anyway? Given Esoteric’s reputation and engineering prowess, I’m inclined to believe the latter, confident that they would not use any technology that would compromise the sound. While the I-03 sounded cooler in my system, this would be less of an issue were it paired with a warmer-sounding speaker (a B&W, perhaps?).

Regardless, the I-03 is capable of handling a wide variety of music. Its strongest suit is classical music, and if that’s mostly what you listen to, the I-03 is a world-class performer worth your consideration.

. . . Uday Reddy

Associated Equipment

  • Speakers -- Wilson Audio Sophia
  • Integrated amplifier -- Jeff Rowland Design Group Concentra
  • Digital sources -- Logitech Transporter music server, Apple iMac running OS 10.7 with iTunes 10.5 and Amarra 2.3.2, Devilsound USB DAC
  • Interconnects -- Cardas Audio Neutral Reference, Halide Design S/PDIF asynchronous USB Bridge with BNC termination
  • Speaker cables -- Cardas Audio Neutral Reference
  • Headphone system -- Sennheiser HD 600 with Cardas headphone cable upgrade, Ultimate Ears UE 11 Pro, Ray Samuels Audio Emmeline The Predator headphone amplifier
  • Accessories -- Audio Power Industries Power Pack II power conditioner; Cardas Twinlink and Cardas Cross power cords; Cardas Audio Signature XLR, RCA, and BNC caps; Cardas/Ayre Acoustics Irrational, But Efficacious! burn-in CD

Esoteric I-03 Integrated Amplifier
Price: $13,000 USD.
Warranty: Three years parts and labor.

TEAC North America
7733 Telegraph Road
Montebello, CA 90640
Phone: (323) 726-0303