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Reader Carlos Martinez Leonor had a good question: "I am reading your review of the Esoteric A-100 and it just comes to me, the idea of tube rolling and tube replacement. Is it possible to do this in the A-100? My question stems from the following paragraph from the A-100 users manual (Esoteric USA): "Specially selected tubes are used for this unit. Special measurement is necessary to adjust the tubes at the time of replacement. DO NOT replace the tubes by yourself." What does it means? Do you have to send the amp to the dealer for tube replacement? Or worst case, to the manufacturer? Can you investigate this while doing the final part of the review? I think this is important because what is the point of automatic bias if you can't change tubes yourself?"


Cough. Mark Gurvey, Esoteric's press liaison in the US, was equally surprised. So he dispatched a query to Hiroyuki Machida at Product Planning in Japan. "The reason we suggest not to replace the tubes by customers is that the bias adjustment needs professional skills and will be pretty much difficult for owners. First of all, the bias circuit of A-100 is not an automatic bias. Professional skill is required for the adjustments. Secondly, the A-100 uses direct-coupled triple stages for signal amplification. This means that the bias system plays a very important part for all of the amplification stages. The adjustment is very delicate. It needs to be adjusted at one of our authorized dealers or at our factory."


There you have it. While Machida-San's answer is likely deliberately cryptic, I read into it that to work as intended, tubes need to be closely matched to begin with, then remaining offsets are manually trimmed which requires affixing probes at various points. The circuit's need for ultra precision spanning multiple direct-coupled stages is apparently incapable of compensating for gross valve mismatches by itself. Back to subjective performance in the listening seat and the remaining question of the direct input's presumed superiority when fed from the matching C-3 preamplifier.


Though counter-intuitive -- shouldn't more circuitry add noise -- the inclusion of Esoteric's preamplifier plainly heightened resolution. This was well documented on Michel Camilo & Tomatito's Spain Again, the winning follow-up to their scorching Spain maiden release. The dense chordal action in the pianist's left hand had more visibility in 'direct' mode. Tomatito's flamenco guitar arpeggios had crisper attacks and dynamics were steeper. In a nutshell, using the A100's input selector/attenuator circuitry incurs shades of softening and thickening. That's modest to be sure. The average 'phile might shrug it off as negligible enough upon returning to integrated use. But chances are that those betoothed enough to play in these leagues will have the ancillaries to demo the resolution gains in very self-justifying ways. If there's a single word to capture the essence of the C-03/A-100 combo, it surely must be utter elegance.


Though bound to be overshadowed by the A-100's sheer mass and sex appeal -- ultra-quiet tubes from Esoteric vs. integrated chips -- the C-03 is one helluva performer. It remains for Frederic Beudot on staff to tabulate the virtues of Steve McCormack's Virtual Reality Engine preamp, an unconventional amalgamation of passive/active elements. I'll merely say that conceptually, operation at zero circuit gain in nonetheless active mode (which is possible also for the C-03 and arguably key for both designs) suggests a certain 'great minds think alike' overlap. Emphasis has to remain on 'certain'. I understand from Steve McCormack that the innards of his unit seem surprisingly vacant. The majority of what makes up his circuit's building blocks lives on the underside of the motherboard and is thus invisible to prying eyes. The C-03 meanwhile is certainly far from skinny on parts density.


To take the latter's sonic measure, comparisons to my tubed ModWright LS/PS 36.5 were in order. Parked in the same price class, positioned as their designers' respective statements, these units also compete for the same wallets. And the ModWright has existing reviews for reference. Aware of my own valved allegiances in the preamp department, I also knew how none other than Brazilian designer par excellence Eduardo de Lima had deliberately authored a non-valve preamp to complement his famous Audiopax Model 88 tube monos. In this context around the A-100 tube amp, would the BurrBrown attenuating op amps carry the day; or Dan Wright's glowing bottles make unexpected must-have contributions to lead the charge?


The Esoteric was silkier and smoother, the ModWright glassier and distinctly more energetic in the lower treble. This was particularly obvious on Camilo's tickled ivories on the mellow Piazzolla tribute "El Dia Que Me Quieras". With the Esoteric, the harmonic decays overlapping the following fundamentals as the maestro from the Dominican Republic descended his keys were clearer. I got a visual of a very tall cabinet with drawers opening, each releasing its note in succession while the drawers above slowly closed for an endlessly shifting progression of multiple drawers being open to various degrees at any given time. A constant turnover of primary notes and decay shades. With the ModWright, dynamic peaks scaled up. With the Esoteric, more profound blackness between the notes made for more pervasive 'damping' as you get from AC isolation transformers. With the ModWright, there were audible auras. They intersected between the performers for a heightened sense of stuff between and around the notes. In short, the ModWright was silvery and charged and more forward, the Esoteric golden-hued and more relaxed and distanced. Not exactly what I had come to expect.

The upshot? In my final review system -- APL Hifi NWO 3.0-GO (a radically rebuilt Esoteric UX-1), Esoteric A-100, DeVore Fidelity Nines -- the ModWright's greater upper mid/lower treble brilliance teetered closer to hard and bright on stiff recordings (say Dulce Ponte's newest live double album El Corazon Tiene Tres Puertas). The less energetic C-03 remained unruffled suave and the epitome of sophistication no matter what. Stunning but never sterile resolution. Surprising myself, I more often than not came down on the side of the C-03. In short, diehard SET man had to call the transistorized Esoteric preamp a monster match for their suave tube power amplifier. Whoda thunk that high-roller chips -- well, attenuator chips with voltage gain run off higher-than-usual rails -- had this level of class up their non-discrete prepackaged sleeves? Well, I know at least one other (ex) valve man who'd not be surprised one wit by these personal revelations: John Stronczer of Bel Canto Design.


Spinning Ohmachi-San's remastered Beethoven Overtures with Sir Colin Davis leading the Bavarian Radio Symphony Orchestra showed capacious layering, dynamic tracking and the kind of transparency which places this type of sound firmly into the upscale transistor area with a goodly dose of modern SET textures -- subtle rather than voluptuous -- folded in for good measure. That seems the perfect characterization to wrap up this review. Ohmachi-San's step on the wild side (tubes from a company known only for transistors) wasn't so wild after all. It deliberately harvests from the glowing bits the specific traits which would appeal to a refined transistor man: delicate textures, truer timbres and treble, dimensional heightening. Discarded are overt euphony or any pronounced effects for that matter. This means also that the typical shadows of weak bass and foreshortened treble have been significantly diminished if not entirely transcended.


Comparisons
The German V80 integrated from Octave competes directly with the A-100 in tube c
omplement (4 x KT88s in push/pull). Even considering the present exchange rate between euro and dollar, its €6.800 asking price without phono stage plus optional €2.250 Super Black Box external capacitance upgrade puts its at $14.000 or 5K less than the big Esoteric. For that reduction in price, you get an RMS power output of 70 watts per side (80 peak) over the A-100's 45wpc. The Octave runs its power tubes in pentode and fixed bias mode, the latter enabling easy tube replacement by the owner.


In matters of truly upscale sonics and ultra low noise, both machines are perfectly matched. Sonically, there are very interesting differences. In Nelson Pass' classification scheme of dominant THD flavor, the A-100 is a 2nd-order machine, the Octave a 3rd-order. This means that the A-100 is sweeter, somewhat rounded on transients, not as separated during dense interludes and not quite as resolved in the depth/layering dimension. Returning to Dulce Ponte's infamous upper-midrange energy -- she's a power belter when she means to be -- the Octave reveals more bite and charge than the Esoteric. Talking in color terms, the A-100 is slightly golden, the V80 possessed of a blueish undertone.


It's important to understand that at this level of the game, so much of the fuzziness and softness of lesser push/pull circuits with their inferior bias schemes has been transcended that in the resultant purity of sound, the remaining THD flavor of the circuit is crystallized as a very fine and steady aroma; a minor spectral shift of stage lighting. The high resolution makes it distinct to hear yet the actual extent of it in the comparison is quite small.


Returning to the 'tube load from hell' of my Mark & Daniel Maximus Monitor with OmniHarmonizer, the physically smaller German amp proved to be more load invariant and damped in the nether regions to drive this 85dB 4-ohm speaker with the endowed midwoofer with true aplomb. To perfection in fact. As stated earlier, the A-100 was looser in its bass grip on these speakers and somewhat overdone in bass amplitude to also hint at a higher LF level of harmonic distortion (higher THD in the bass will always make the bottom end sound louder, albeit less indistinct).


In matters of raw grunt and sheer control, the feedback-controlled German amplifier thus goes farther. Preceding the A-100 with Octave's top preamp, the HP 500 SE, showcased how the latter's 'blueish' pentode aroma could be grafted onto the Esoteric's more single-ended triode flavor. It also confirmed, as the C-03 already had, that running the A-100 as a power amp does reap sonic rewards over integrated mode, albeit at the obvious cost of whatever your chosen preamp adds to the final bill.


Wrap
Unapologetically, the A-100 requires a serious commitment of green. And real estate. Plus, the C-03 has every creature comfort imaginable. And runs 'lowly' ICs for voltage gain. The stuff is also built like vaults and weighs the business. If we said nothing else to add up just this isolated tally, it might scream luxury toys for flash-consumed jet setters. Yet that's completely overlooking that the man who holds the vision for this company doesn't particularly cater to the Cartier mind set. Other than sharing with the well-heeled an appreciation for ultra-quality finish and design integrity that is. As serious R&D bequeathed constantly on his VRDS transports during this USB/hard-drive transition shows for just one example, Ohmachi-San remains madly committed to expert mechanics. You might disagree how much some of this mechanical overkill ultimately matters in the listening seat. But you can't fault a man for setting himself very high standards.


With today's 20th anniversary celebrants, those very high standards include far more than material worship. Serious performance in other words. Whether rightly or not, it's something Bang & Olufsen's equivalent chops in industrial design rarely get credit for. Related beliefs that just because a large company makes superbly finished expensive audio would automatically disqualify it as sonically compromised should completely miss the picture of Esoteric's new C-03 and A-100.


In conjunction, these two components perform as though they were made for each other. Which they clearly were. These intimate results take a modest backward step when the C-03 is omitted to run the A-100 source-direct. Esoteric's new preamplifier is ultra-smooth and silken, terrifically resolved yet not sterile. It's plainly not an externally gussied-up but internally old-fashioned passive design which dilutes vitality and undermines emotional integrity. Rather, it seems to offer the extreme ambient recovery of true passives like my Music First Audio TVC with the subtle textures of a wide bandwidth, very subtle valve pre like my grounded-grid Wyetech Labs Jade.


Esoteric's convertible valve amplifier produces advanced zero NFB triode treble from phase-splitting KT88s; adds drive to power most reasonable speakers; avoids the thickening of musical strands with its concomitant subliminal blurring that at least to this listener seems endemic to most push/pull amps; and offers low-noise deep-down resolution of the sort diehard transistor aficionados insist on. The A-100's only limitation is quite in keeping with its concept: brutish bass systems with very low impedance will reveal its high-ish output impedance and rising THD into such loads' lower bands. Otherwise, it offers a very rare combination of sonic virtues for a mid-power push-pull valve amp. Only time will tell but I believe that purely based on performance -- let's eliminate price from this picture for the moment -- this amplifier might one day be regarded as a true classic which successfully bridges SE and P/P virtues. What a way for this company to celebrate its 20th anniversary. Congratulations, team Esoteric and Ohmachi-San!

Quality of packing: Triple cardboard with foam inserts and protective cloth bags. Doesn't come better.
Reusability of packing: Definitely.
Ease of unpacking/repacking: Very easy but beware the substantial weight of the A-100.
Condition of component received: Flawless as is typical for Esoteric.
Completeness of delivery: Perfect.
Quality of owner's manual: Very good.
Ease of assembly: None required.
Website comments: Quite informative but improvements for in-depth product descriptions could be made.
Human or web interactions: Prompt, professional and courteous.
Pricing: Luxury goods with concomitant tags.
Final comments & suggestions: In a perfect world, the A-100 wouldn't rely on a dealer or the manufacturer to eventually replace its power tubes. That said, tube rolling in general is discouraged as Esoteric has voiced this circuit around the supplied valves and taken pains to outfit each amp with stringently tested, matched and pre-conditioned tubes.
Esoteric website