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In general, speakers like the Dynaudios were best teamed up with the Philips DVP-9000S. If the amp was the NuForce Reference 9, I definitely threw in the Audio Zone Pre-T1 passive preamp, for a good measure of pure transparent no-MSG taste. Actually, that's one of my reference systems. But with the Kallisto, I needed more preamp gain and most of the time settled on the Dared SL-2000A. This combination had a very organic feel. Instruments with resonating chambers benefited further from a certain wooden overtone added to the palette. It wasn't quite nasal but close and actually quite charismatic. One CD that would best illustrate my point is Original Music for Cello and Guitar [EMEC E-001] played by Michael Kevin Jones on cello and Agustin Maruri on guitar. This CD is one of those 'demo' discs preloaded with audiophile attributes. Burgmüller's "Nocturne" is an instant pleaser. The Kallisto/Dynaudio
combo delivered the velvety cello sound and pearly guitar notes with the right amount of microdynamics depicting bowing action and fingernail dexterity. Max Baumann's "Hommage á de Falla" is a fiery virtuoso warhorse and the combo exemplified it with gleaming sparkles and electrifying picks. The Kallisto had enough vigor to emboss the Dynaudios for sure.
When I replaced the Dynaudio with the Unity Audio Inner Spirit, my eardrums felt like pupils moving from dark to bright light. It took a while to adapt and appreciate a different kind of sonic characteristic. What seemed to be harsh and shouting in the beginning gradually became clean and articulated. Though with limited bass extension to only 59Hz, the 4.5" Fostex widebander seemed to surpass the Dynaudio in ultra-high frequency extension and did a reasonably good job in imaging and detailing. Although the organic wooden overtone diminished, the guitar strumming was definitely spicier. An interesting comparison could be demonstrated with two CDs from
the same collection: Rossini's Complete Works for Piano Vol. 5 and Vol. 7 [Channel Classics CCS SA20504/24106]. Pianist Paolo Giacometti plays on an 1837 Erard in the first CD and on an 1858 Pleyel in the other. While the Dynaudio furnished the Erard with a very nostalgic wooden nasally sound, it was the Unity Audio that provided a more pronounced distinction between the two period instruments. The Pleyel sounded more strung up, primitive and shallow in harmonic terms. The Erard, despite being 21 years older, sounded fuller and richer, with more interesting shades of bolder tones and colors akin to modern pianos. I'm not in the least trying to imply that the Unity speaker was better than the Dynaudio. It so happened that with these recordings, and perhaps due to the lack of bass extension, the Unity managed to expose the major difference between the two pianos better. Therefore, it didn't surprise me that when I played Dvořák's Hussite Overture and Bloch's Concerto Grosso again, I had to switch back to the Dynaudios. The Facette beautified everything to the right extent.
There are so many variables in a system that can and will fine-tune the Kallisto's sounds. For my tastes, the most authoritative balance between musicality and resolution and versatility of repertoire came from the combination of Philips DVP-9000S, Dared SL-2000A and two Loth-X BS-1 per channel stacked as d'Appollito arrays (connected in parallel to 4-ohm
taps). It'd have melted your heart with Neemi Järvi's insightful reading of Tchaikovsky's Pathetique Symphony [BIS-SACD-1348] and set your adrenaline pumping with Jaz Coleman's arrangement of The Symphonic Music of Pink Floyd [Point Music 446 623-2]. Replacing the Dared with the Audio Zone Pre-T1 achieved yet higher resolution and transparency but traded off in warmth and bottom octave heft. As far as interconnects, speaker cables and power cords were concerned, I did try enough mix'n'match to conclude that none of them showed any adverse effects. I'd like to keep that part of the report out of the discussion however to avoid getting into micro subtlety and mega subjectivity.
Not all 300B amps are created equal and indeed, they can sound drastically different. Suppose that on a scale of -5 (the least valve bloom) to +5 (the most valve bloom), KR Audio is -5, Audio Note +5 and Song Audio +3? Where sits the Kallisto? Using the Restek Radiant CD player and Klipsch Synergy F2 as my references for neutrality, I invited my friend Frankie to bring over his KR Audio 18 BSI to do an A/B comparison.
Under the KR brand, tube guru Dr. Riccardo Kron materialized his
ideal world of tube and transistor united. He called it Vacuum Transducer, which by his definition was vacuum transistor without the transistor. The KR signature sound therefore is, according to KR, warm and rich as a vacuum tube yet fast and transparent as solid state. Ask any KR fan and the answer of course is affirmative. Ask an Audio Note fan and be prepared for a heated debate. The KR 18 BSI uses a pair of 300Bs which are KR's own. This one-of-a-kind 300B has exceptionally high voltage and current ratings and therefore is categorically not interchangeable with fellow 300Bs. Its operating temperature requires a special cooling gel and metal heat sinks. With these muscle tubes on board, KR's Model 18 integrated amp is capable of 25 watts per side rather than the usual 8 for three times the power.

This comparison soon proved to be disadvantaging the KR unit. Frankie had been using his with an Atoll CD player and Klipsch La Scala speakers for amazing results. I'd auditioned that setup and told Frankie that it was the best La Scala sound I'd ever heard. Although the Synergy F2 retains some of the Klipsch signature sound, its smaller cabinet and fewer horns actually gives it a faster, more dynamic modern sound. With the KR, all these improvements were ironically translated into adversities, particularly with certain kinds of music. Chamber music and vocal were graceful and suave, with very cohesive tonal balance and fine texture. It was orchestral bombardment that shattered my steroid 300B dreams. I said bombardment deliberately because the KR amp really made forte tuttis in the "dry" recordings mentioned earlier assaultive and abrasive.

On the other hand, the Kallisto's sails were getting all the wind blown in their direction mated to my Symphonic Line RG3 Mk III preamp. Don't let yourself be misguided by that preamp's highly advanced modular circuit board and glossy high-tech metal chassis. Most people concur that this preamp is actually a solid-state implementation with a valve heart. It also happened to be a highly complimentary match for the Kallisto which, I now believe, was designed with the same principles in mind. Ably augmented by the Synergy F2, which is also designed to bridge resolution and musicality, I think that I have indeed found the 300B of my dreams. All the qualities the 300B is famous for are present in this combo, with spontaneity, conviction and aplomb.
Technical confirmation
Looking at the specs, the Kallisto Sinfonia 300 demonstrates nothing special: 8 watts per channel at 3% THD + N, frequency response of 20 to 24,000Hz +/- 1dB, S/N ratio of 85dB (A weighted). Inside the chassis, nothing really jumps out and grabs you. It's the actual audition that floored me. I must reiterate that I've been searching for my 300B dream amp for many years and have heard, including this one, eight in total now (two of them were paralleled 300B configurations but I prefer single-valve SETs). I must confess as well that I have developed my own preferences which may not necessarily meet with other people's approval. At this point, it's beneficial to all concerned if I quickly ran through the 'unorthodox' approach of the Kallisto technicalities that contribute to the sonic behavior I happen to fancy.
Most tube gurus will prefer manual bias for the obvious reasons - it feels more professional, sophisticated, 'in control' and provides more power. However, the Kallisto has opted for auto-bias in the name of reliability and stability. SET purists, for nostalgic sentimental reasons, condemn negative feedback. However, the Kallisto administers minimal negative feedback for equilibrium. Negative feedback was an invention that arose around 1950. Purists who glorify tube amps as reliving the past will not live with negative feedback because it's modern technology. It's a matter of principle if you like. But when
you look at it objectively, zero-NFB is an ideal circuit that works best in an idealized world where all power companies maintain regulated wall power voltages and all vacuum tubes have 100% compatible ratings and never grow old and weary. It's what experienced pessimists would call an experimental circuit or textbook circuit and what inexperienced optimists would call sacrilege. In the real world that is bedeviled by uncontrollable variables like voltage fluctuations, NFB acts as the most viable governance for stabilization and regulation. It minimizes the difference between old and new tubes, lowers output impedance for better damping and reduces noise.

Regarding tube appointments, the Kallisto is quite conservative. Two Sovtek 5U4G tubes (one per side) are employed as rectifiers for double safety. A soft start is added on the AC input to minimize start up transients. Two 6SL7 tubes per channel handle voltage amplification, then impedance matching before the first-stage signal is passed to the power tube. Some amps skip the impedance matching tubes to save costs and end up magnifying the 6SL7 distortion. The heavy duty power transformer is an over-spec'd toroidal type with ample headroom. It has been tested for continuous operation where temperatures remained within 45°C to 48°C, well below the Canadian requirement of under 65°C. The output transformers are silicon-steel hand-wound audio grade which were bench-tested with a square-wave generator to exhibit vertical leads which denote very good transient response. (The technical details and bench test results were provided by my tube expert and engineering friend who modestly prefers to remain anonymous.)

Conclusion
Back to my theoretical scale of -5 (KR, little valve coloration) to +5 (Audio Note, the most valve coloration), the Kallisto Sinfonia 300 sits somewhere between -1 and 0. Call it neutral, call it the best of both worlds. Call it bridging the gap, call it compromise. Whatever. For me, it's the best contender to fit my criteria of dream 300B amp - and I've heard 300B amps from Pacific Creek, Dared, Audio Space SET and PP, Audio Note, Song Audio, KR Audio, Antique Sound Lab PP and others. The only reason I am not writing a cheque is that I promised my wife not to purchase anything audio over 50 pounds in weight again. However, the Kallisto will be the yardstick and reference in my ongoing quest for my 300B amp. Perhaps by keeping the sweetest dream a memory, knowing that it's within reach and attainable yet not realizing it in this life, I'm guilty of romanticizing my obsession. But if I may recommend a dream or fantasy, here's my dream machine (minus the weight): the Kallisto Sinfonia 300, for romanticizing valves without indulging the sentiments.
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