Aries Cerat Kassandra MK2 DAC review preview

Both Aries Cerat as company and Stavros Danos as the owner/mastermind behind the brand is hard to pin down. You can contemplate on the design, exotic circuits and state of the art oversized implementation of the elements, yet, until you’re not heard any of their products it will be just a pure sonic speculation. 

I’ve had a luxury of listening to their phono preamp few years back and got hooked, but the real step forward in my appreciation happened at my visit to the Greece where I could experience the full blown Aries Cerat ultra high-end audio system. 

Aries Cerat falls into the very niche category of extreme ultra high-end audio where things are done in very sophisticated and elaborated way. Quite the opposite to the “ordinary” high-end audio venture. 

These days I’m trying to do my homework more deliberately and invest my time in people behind the brands. This means meeting the persons responsible for the design and trying to understand their mindset and audio philosophy. This takes more time, but I more and more prefer to do things in such prolific way. There are vast offerings of mediocre high-end gear out there and more then enough publications are ready to swallow anything. I try to differ and when its possible I’m dedicating my full enthusiasm and attention to the people, products and brands that fires up my inner audio clock and addresses the qualities most important to me.

So what is so different with Aries Cerat?

Well, what else then the person behind it. Stavros Danos is an extremist by nature and a man that cannot stand still at any point. When meeting him in Athenes we spend days and hours addressing different topics of interest. It was really inspiring and most positive experience. Stavros is both bold and humble at the same time. True rarity these days in the world of endless hollow ego mind trips. A healthy dose of boldness, that comes from hands on experiences and actually mileage let him creates the high-end audio gear that stand out and differ by far. All this goes way back to his younger age, to be exact, it started when he was 14 years old. Not many people know, but he was a prosperous aeronautic engineer with quite few perfeto career offerings from most distinguished international aerospace  companies. He has chosen a different path and something that he loves and cherish most dearly. The music! 

Stavros Danos let his creations speak for itself. They are his “babies” and carry strongest message. Ad hoc Stavros is not only in being able to ride the wave of the past… He’s innovative mind  constantly challenges the level of his know how. This is the only way to do things in ultra high-end audio and something I’ve encounter with few other people in industry like Robert Koch, Rumen Artarski, Angel Despotov, Lee Paul Dalby etc.

There is no simple and quick way of designing something special in audio. It takes a continuing efforts and deepest understanding of the inner workings of electronics. Even with the talent you can go as far. There is a constant push forwardness to it. Even by reaching a certain plane there is no stopping. This falls into the category of literary 24/7 job. These people are driven with the passionate perpetuum mobile self mechanism, that cannot be taught or bought! 

Stavros Danos is without any second thinking a member of this extreme league of distinguished audio gentleman. Not always a title and throne of most desired endeavors. We’re talking about the plane where even most exotic designers stops and settle with  the results and stops. Rare people like Stavros won’t aline with this criteria. This is why his gear is mightier in size, uses large sized components and source the materials from other industries when typical audio supply chain fails to ensure the needed. Satirically, but down to the bone true. Aries Cerat products are not oversized. They are what Stavros like to point out, just properly designed.

While in the process of setting up and building the company, at the most early stages, the need of a true SOTA source was mandatory for Aries Cerat. You can not claim to built speakers that aim to be the absolute best, top amplifiers designs and so on if you do not have a true reference source. And for Stavros Danos reference means the reference in the true context. The source must be absolutely perfect in order to create something special and of difference. 

Stavros began developing the Kassandra as He felt no source on the market would stand up to the task. “There would always be a certain character, lack of dynamics, lack of musicality and true analog-like timbre and flow… and this drawbacks would project to our efforts to create the best speaker-amplifier combo possible.”

The Kassandra’s prototype was developed very early, not as a commercially available design, but as a cost no object lab tool, Stavros personal reference tool for speaker and amplifier development. The decision to be put on production and to be commercially available, was decided at a much later stage.

“We found since then, many new converters launching daily, with impressive specs on paper, but they fell short of what we call analog sound. They always presented, electronic signature that gives digital reproduction a bad recognition. Stavros aim was making a true analog source, which happens to take Ones and Zeroes as input. “And I feel we succeeded.”

When taking things to the extreme only ladder DACs are able to offer the utmost performance.

Ladder DAC is a resistor network switched by a number of switches, n being the bit depth. It is a passive sort of  procedure, where the Delta Sigma technology, while still in developing and moving forward is a complete different conversion procedure.

Delta Sigma converters were developed because it is many times cheaper and easier for the IC company to make a Delta Sigma modulator. Manufacturing a R2R DAC, which includes costly procedures like laser trimming of the resistors to an accuracy of 1/128000 it’s value is a completely different, time consuming and costly operation. Accuracy needed to create a linear R2R converter is of different plane.

Creating analog signal from noise shaping, as in Delta Sigma conversion, sounds counter intuitive. While the very complex, very high order filters that are implemented to reconstruct the analog signal, from burst of noise, makes a good job creating very good specs on the paper fails sonically. High complexity of the filters, and the very high energy of several KHz-MHz noise being present is what gives all the Delta Sigma converters their distinctive sonic signature. A sonic attribute often associated with the term of the digital sound.

Back in R2R principles. The individual resistors, must be laser trimmed to a incredible accuracy, while making extremely high accuracy measurements. This process is unfortunately not available for small batch manufacturers. It is practically  impossible to achieve the accuracy of integrated circuits with discrete resistors. Even the random solder resistance might ruin the low level linearity.

Arie Cerat choose R2R IC, specifically much appraised AD1865Nk converter. Many DACs use the IC converters in the usual “data sheet application” circuit simply adding their analog stage and voila.

Stavros Danos deliberately designed a converter, that uses a number of IC R2R converters as components to a complete new converter system.

The AD1865Nk has a very straight forward data handling logic and does not process the data stream in any way. This gave the Kassandra DAC a freedom to fully exploit the IC its converter system.

For example, the input data is latched and directly refreshes the resistor network with absolutely no additional complex logic or data handling/processing.

Aries Cerat unique SuperClock circuit directly re-clocks and drives the “refreshed” signal. In this way absolutely no additional jitter is induced in the conversion. This is not possible by any other IC converter as there is always internal logic and data handling, that vastly deteriorate the jitter performance, even if the clock input is close to being perfect.

Massive banks of the IC converters act as parallel switched resistor ladder converters, thus canceling the deviation of the actual resistor values vs the theoretical. If the deviation of the resistor value from ideal is Gaussian (which it is),as the number of parallel resistor networks increases, the deviation from the ideal norm is driven to a Zero. This is why paralleling R2R converters, improves linearity.

Noise figures are improved, on the same principles.

The Kassandra converter is working in complementary mode. This translate to each channel being consisting of two converter banks which are “mirrored”,perfectly synchronized and matched, consequently improving the low level linearity (the linearity near “zero” value) as well as it lower noise.

The Kassandra was developed to be an absolute audio source, not just another DAC on the market. Stavros pushed the limits to the max and walked an extra mile on many aspects wanting to have the best for their product development.

Many technical solutions implemented, are not usually found in commercial DACs, as the Kassandra was not developed to be one of them.

Lumitrons displays were adopted from Aries Cerat preamplifier line. They are small glass tubes with tiny filaments, positioned in a way that they from the usual seven segments display figure and  independently lid to form the respecting alphanumeric symbol. It serves no other purpose as to look they way they do. It takes extra man-hours installing and hardwiring them. The result is more then worthy. They look timeless and special with their own specific aura. This is something that LCD or LED based displays certainly lacks off.

The endless war on the jitter is fought in Kassandra with many techniques regarding lowering and canceling it in both passive and active ways.

Bouncing signals, overshoots, low rise times etc. greatly increase jitter. Stavros Danos solve this by using special driving circuits and carefully tuned digital line terminations for all of the digital signals.

Crosstalk between digital lines, ground noise and power supply noise is a major source of the jitter. Kassandra implements an  extensive LC filtering (using high loss RF chokes and high speed capacitors) with all of the ICs,power rails and logic circuits in dealing and solving this problem.

Jitter originated in USB and SPDIF/Toslink sources is eliminated right at the conversion-enable line, or the ”refresh” signal point of the converters.

By implementing the IC’s there is no complex data handling logic and no multi stage data logic, the highly precisely timed signal resolves in a extremely accurate jitter free conversion. This is not possible with any other converter.

The Super clock  upstream reclocks the XMOS asynchronous USB controller, as well as the SPDIF receiver.

Jitter is very audible and I Stavros strongly felt that the dichotomy must end. That is why the digital input re-clocking circuits are bypass enabled on the fly and every demanding audiophile can make an AB comparisons the fly with the turn of a knob.

The R2R IC’s are current output devices. Their impedance is very high and close to an ideal current source and the current must be converted to a voltage. Most converters involves Opamp circuits, from complex virtual ground schemes down to simple circuits using a resistor for making the IV conversion, followed by a buffer.

Aries Cerat Kassandra two complementary output converter banks operate in differential current mode. This must be converted to single ended voltage output and Kassandra employs specially designed transformer, that converts the current differential to a single ended voltage output.

Many argue that the best current to voltage converter is an inductive element. Stavros Danos avidly follows this logic as he feel that the performance acquired from the specially designed transformer is second to none compared the many alternative IV methods that he tried and compared extensively. 

The analog stage in Aries Cerat Kassandra DAC is a small Single Ended tube amplifier consisting of a transformer loaded tube driven directly by the IV transformer and biased with the ultra low noise bias power supplies. E280F tube was chosen for a reason as its a best sounding tube from the Super tube family of valves It is a triode connected and with a specific parameters like transconductance, plate impedance and especially linearity and noise levels above any small signal tube.

The triode is loaded with a special quality large core step down transformer. The SE triode amplifier is fed by super sized power supplies, double filtered with chokes and high speed, high energy capacitor banks.

As you see, nothing with Kassandra is left to chances and designed in a simple way. This shows in its sound and in what way the Stavros Danos logic translate to the music. 

Technical part of the Kassandra is being addressed so far. Now to the logical progression and big question. All the complexity and exotic take on electronic means a little without taking the sound to the upper echelon stratosphere. Where does Aries Cerat Kassandra DAC belongs?

Sound performance was as resolved as the technical digital approach. Kassandra pushes the analog to digital conversion into the new realms and especially for the given price represent not only true audiophile gem, but a bargain compare to what some much bigger and established names are charging for their high praised products. Its is one thing to buy your reputation and reviews along the way. Truly deserving it is a completely different story….

Let me dive into the sublime universe of the music with the guidance of Aries Cerat audio submarine…

János Starker Variations on the theme by Paganini KODALY is my to go album for late night listening, recouping and critical listening. I simply adore János Starker ardent virtuosity. He can encapsulate the raw pureness of music without any trace of the clinical agenda. That is not rare. Its precious. Many of the audiophiles and music lovers strive for Yo-Yo Ma more “soft” and “sweet” output. I’m strictly after the raw emotional interaction. My hearth is locked on Starker’s lyricism and unabridged rendition of Bach, Paganini, Kodaly…

Aries Cerat Kassandra presented this album with ghost resolution, marvelous transcription and with complex flamboyant energy. This level of raw energetic impact and details presented was a complete surprise and an instant enigma resolving further with Joe Pass’ Stella by Starlight from his legendary album Virtuso. Two different instruments both never easy to reproduce with the full contour and potency via digital source were formed non restrained and sonically refined with forthcoming variableness and richness of captivating string decays and delays. Something that conventional types of DAC’s are unable to even come close to. And what to talk about the transparency and details being resolved…. 

When dealign with the reconstruction of the overlapping notes of the string instruments in most cases and even with top tier digital front ends actual presentation lacks the absence of the truncated notes phenomena. With real music, when the decay of the former note is still being present and new note is being introduced via the fingers or via bow the multiplex harmony evolves. Things go nutty pretty fast when DAC cannot follow the reflection and harmonic decays instead of materializing without any timbral gaps, becomes a lifeless and absent of harmonic richness. There is no continuity equation being mandatory for any serious reproduction. Stand stillness appears leaving the un-involving. lifeless audio experience. Instead of notes being filled and lined up without any gaps usual digital reproduction introduces low res grained resolution. On contrary Aries Cerat Kassandra palpable contour and harmonic richness strikes  immensely with a rocket speed. Kassandra easily conveyed sempre staccato with slight rubato. Where usually notes become slur Aries Cerat DAC resolved the floating nature as most natural way of transcribing. Capricious pace mating with the best attributes of analog reproduction. 

While other DAC’s might be on the level of Vieux Château Certan, Latour à Pomerol or L’Église-Clinet; Aries Cerat Kassandra nails it with the richness and completeness of one and only ’61 Pétrus. 

To be continued…

Text/photos: Matej Isak