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Coda Continuum Unison integrated - Further
thoughts on a long term commitment
The Coda/Continuum Unison has been my reference amplifier since I reviewed it last October (see Issue 9). In other words, I bought the review sample. I still own my Marsh Sound Design separates, and use them for equipment reviews on occasion, but with my system tucked into a more compact space than in my bachelor apartment, an integrated amp is a more practical choice, and the Unison Ultra is an exemplary reference—clear, uncolored, powerful, and controlled.
When I heard that Coda (Continuum is the manufacturer's "affordable" product line) had designed an Ultra version of the Unison, I got myself in line for the upgrade. The Ultra retrofits key parts and design elements from Coda's newest S Class amplifier series, including thirty-six custom Mills emitter resistors and IXYS fast recovery diodes. Power supply capacitance is increased by 80%. The damping factor, via the Mills resistors, is increased by 60% for lower output impedance. There is also a new, fully enclosed transformer of slightly higher VA (i.e., power). What all this means, according to Coda, is a refinement in the mid- and high-frequency areas, with more liquid highs and improved low-end control.
I pieced all this together from Coda's product literature and website, but when my amplifier was returned as a Unison Ultra after a two-month wait, I didn't really care how it was supposed to sound. I was just eager to listen. What I heard from the outset was an amp that was even cleaner, more extended, and more dynamic than its predecessor, and the original was no slouch in any of those areas. As might be expected, there were traces of thinness and constriction out of the box, and the sound was a little bright, but as the Ultra broke in, those traces of hardness faded away, leaving a stunningly pure sound from the top to the bottom of the frequency range.
The high end was a bit more extended, and considerably more refined. The Ultra upgrade swept away what little grain there was in the original amplifier's sound. While the top end improved qualitatively, the bottom end was enhanced quite quantitatively. The Ultra brought out the deepest bass I'd ever heard from my Harbeth Compact 7 speakers, and that bass was tight, controlled, and not the least bit tubby (the latter is a sometime criticism of the C7s). The Harbeths' trademark is their even and natural tonal balance, and the Unison Ultra helped them deliver that glorious balance extraordinarily well. The fact that I picked up 25 watts of power in the upgrade (from 125 to 150 per channel) was also evident. The Harbeths don't need a lot of power, but they like it, and the additional headroom and sense of ease were obvious.
The Unison also has a rare and highly useful feature—the ability to adjust gain in the preamp section. The amplifier's gain is 26 dB, to which the preamp adds a further 14dB, but you can trim the preamp section, decibel by decibel, and as you bring the amp closer to unity gain, you achieve a subjectively lower noise floor and a more musical, refined presentation. With the preamp gain all the way up, the Unison has a little too much sizzle for my taste. At unity, it needs a good deal more goosing via the volume control to arrive at an appropriate level for music. I have found a happy midpoint, and this setting delivers both refinement and balls.
Good LPs from the 1950s often have a fabulous midrange but not much action at the top or bottom. It's similarly easy to hear the characteristics of multi-track recording equipment from the 60s and 70s, to the present day. The Unison Ultra is incredibly good at revealing the nuances of a particular recording or remastering. By contrast, the Shanling STP-80 integrated that I reviewed last month had its own sound, and it applied that sound to almost every recording. It was a nice sound—a lush, seductive sound—but the Unison Ultra is in an entirely different class in terms of transparency and resolution.
This was made evident by a spin of the 2003 CD reissue of Ben Webster's Soulville, a famously warm and beautiful recording. The Unison delivered that beauty in spades, while revealing every detail with perfect clarity. Herb Ellis plays electric guitar through a mid-50s amp that frequently distorts despite the quietness with which he plays. Through lesser equipment, it can be hard to tell whether the distortion is coming from the amp, from tape overload, or from your playback system. The Unison Ultra lets you know exactly what's going on. Its pinpoint staging plants Ellis and every instrumentalist on the stage with precision, depth, and uncanny presence. Big Ben's breathy technique, very close-mic'd, is captured in stunning fashion, as are Ray Brown's bass and Oscar Peterson's piano.
Since my original review, Coda has streamlined their complicated product offering for the Unison. There used to be three versions of the amp at different price points, and within each price point there were further choices to make regarding power rating (100, 200, or 300 watts) and aesthetics. Now, there are only two versions available—the basic Unison ($3750) and the Unison Ultra ($3950), which is so clearly worth the extra $200 as to be a no-brainer. A hefty universal remote, the best I've used, is included with both.
This amp is so good that I am challenged to find caveats. I can only think of one. Although the Unison Ultra has little character of its own, it definitely has a solid-state signature. Those who prefer tubes may interpret its utter cleanliness as sterility. I don't, and find the Ultra to be just about the best of all worlds at its price point. It's closer to fast ‘n' lively than it is to warm ‘n' lush, but the amp's strong rhythmic sense does not come at the expense of its instrumental timbre, which is superb.
The bottom line is this: With the Unison Ultra integrated, I have arrived at my destination, at least as far as amplification. I can't imagine any amp being appreciably better without the kind of capital investment I am not prepared to make. I would love to upgrade my aging VPI turntable, see room for improvement in my Sony digital player, and would be willing to experiment with a new phono preamp, as much as I love my E.A.R. 834P, but the Unison Ultra now joins my Harbeths as "solved problems" in my system. Those don't come along every day. Tom Campbell