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Set to zero gain turns the C-03 into a passive. Running off +/- 38-volt supply rails regardless -- Godzillacious for a preamp -- makes it very very active. As a result, there is none of the harmonic bleaching and dynamic wimpiness one expects from traditional passives whenever those are compared to truly superior actives with open-minded ears.

Still, Esoteric's C-03 is ultra transparent and truly adept at retrieving subtle ambient cues for that surprising "I can hear the recorded rear wall" type of soundstage panorama. Without fail when the recording allows it, that superimposes a different acoustic on your room. As might be expected then, depth layering is superb. Words like cavernous, intelligible into the far reaches and dimensionally resolved all apply in spades.

Texturally, the C-03 is mostly absentee but it does infuse its water-like though fresh rather than stale purity with a whisk of oiliness for that subtle silky texture which is apparent particularly in the treble and in fact more sophisticated than some of the 'hotter' valve preamps. But it's not only the adjustable gain structure (0, +12dB, +24dB and +/-18dB of input trim) that makes the C-03 a convertible design whereby its output voltage relative to the volume control's setting is adapted. It's flatly a great sonic tuning feature as well. For more dynamics and stronger bass, choose higher gain. For more transient energy and greater subjective speed, select no gain. It's something you can experiment with on the fly.

Which brings us to user-friendliness over which Esoteric's engineers clearly labored with a Zeiss magnifying glass. From input naming to skipping inputs and deleting outputs; from balance control to the various gain and input sensitivity options; from inverting XLR pin configurations to being able to access a 2-option mini sub menu with a brief prompt and the full menu with a longer prompt of the same button on the remote; from display dim levels and back-lit remote buttons to the automatic disconnect from the circuit of all input grounds except for the currently active... the C-03 really is a poster child for extreme user convenience and thoughtful features.

Built like a tank, cosmetically elegant and non-frilly, full-featured in the best sense of the word, Esoteric's C-03 also is the ideal mate for upscale triode amps of Ancient Audio or Yamamoto pedigree. Such amps are so finely balanced in the harmonic domain as to neither require nor desire any dilution, alteration or shifts in their voicing. What they thrive on is an ultra-quiet supremely resolved signal of 'supercharged' voltage swing potential to pass on the utmost in dynamic expressiveness.

That's the Esoteric. I'm sorry for the Music First Audio gang but the C-03 eats their Passive Magnetic TVC or transformer volume control for breakfast. I own one so this isn't empty banter. Transistor amps looking to supplement their harmonic income with a thermionic stipend of course won't really find it in the Esoteric. While the C-03 is texturally suave -- elegant is the word -- it doesn't enhance. And some transistor systems are looking to be enhanced. Which doesn't necessarily require valves as Frederic's review of the op-amp powered Accustic Arts Preamp I Mk3 proved. But there's a difference between warmth that's a function of smoothed-over transients (often from timing errors); and tonal complexity in which the entire harmonic envelope is fully and evenly elucidated.

The Esoteric passes what it is fed but acts somewhat like a pressure tank. Clean slow water enters on top of the reservoir, clean pressurized fast water exits at the bottom after falling down from great heights and being funneled through narrowing pipes. Dynamics and resolution increase -- the S/N ratio of this device has been pushed hard -- but the clarity of the medium otherwise remains unaffected. The gain setting is an extra valve that allows you to regulate some of this pressure to your liking.

After my review of Esoteric's first valve amp for which the C-03 was sent along and featured in a supporting role, both pieces were returned to Japan. In the meantime, I did acquire a personal unit again directly from Japan. You could say that I missed it after the motto that hindsight makes wiser and you don't know how good you had it until she walked out. Fortunately, machines can be replaced. My hardware inventory for work and pleasure now includes valve and transistor amps of the low and high power persuasion and, as of late, the equivalent options in the preamp sector. My ModWright DM 36.5 is the weapon of choice for the FirstWatt F5 and ModWright KWA-150, the Esoteric C-03 the perfect companion for my 45, 300B and 6C33C SETs.

Lastly, the C-03's functionality makes it a terrific reviewer's tool. For one, the gain trim per input makes A/B comparisons between sources of different output voltages child's play. Two, switching the display to show actual dB of attenuation wherein 0 means loudest (no attenuation) and 99 mute (full attenuation) becomes a very practical confirmation on how much gain a particular review system 'burns up'. It's mostly far less than pushy salesmen would have you believe.

It's popular to end a review with "I liked it so much, I bought it". In this case, I'd written the review and returned the piece. Many months and a move from Cyprus to Switzerland later, I bought one back, no further comments implied or necessary. But two opinions are always more informative than one. With Frederic's formal follow-up, this opportunity arose to openly declare to Esoteric's C-03, "I'm sorry I let you get away the first time". I'm sorry no more...