Description

Aries Cerat Ianus Ithaka DAC

The Ithaka Digital-to-Analogue Converter from the Aries Cerat Ianus Series represents a bold step forward in the evolution of high-end digital audio. By combining one of the company’s most advanced digital conversion platforms with its latest TriodeFet analogue output stage technology, the Ithaka redefines what is possible from a digital source component.

Developed from experimentation inside the Aries Cerat laboratories, the Ithaka emerged from a simple yet ambitious idea: what would happen if the highly refined digital engine used in the flagship Kassandra Limited Edition were paired with the newest generation of TriodeFet amplification technology? The result of that curiosity is a converter that merges extreme resolution and digital precision with the musical authority and drive normally associated with powerful analogue amplification stages.

The Ithaka therefore stands as a unique digital source, designed to combine cutting-edge conversion with a powerful and ultra-linear analogue stage.

Design Philosophy

The Ithaka DAC was conceived alongside the development of Aries Cerat’s newest generation TriodeFet technology, which also appears in the company’s flagship Aries Cerat QuintEssence Amplifier. This technology represents one of the most advanced line-level and medium-power amplification platforms created by the company.

While Aries Cerat already employed the Inverted Triode topology in its flagship digital converter, the Aries Cerat Homerus DAC, the concept of combining the digital bank architecture of the Kassandra platform with the new TriodeFet stage initially existed only as a theoretical idea.

Early prototype experiments quickly demonstrated that the concept had extraordinary potential. The resulting design delivered remarkable sonic authority, scale, and transparency, convincing the designers that this hybrid digital-analogue approach deserved full production.

The Ithaka therefore became the final expression of this experiment: a digital converter that integrates advanced R2R conversion with an exceptionally powerful analogue stage.

R2R Ladder DAC Architecture

At the heart of the Ithaka is a pure resistor ladder DAC topology. In a ladder DAC, digital data controls a precision network of resistors that convert binary information directly into analogue voltage.

This approach avoids complex digital processing stages and preserves the integrity of the original data stream. The conversion process therefore remains extremely direct, allowing the musical signal to retain its natural tonal structure and timing relationships.

Unlike many contemporary converters, the Ithaka avoids delta-sigma architectures and digital filters. These approaches can introduce artifacts that affect musical flow and tonal authenticity.

Instead, Aries Cerat selected the classic Analog Devices AD1865N-K R2R converter chip, widely respected for its natural tonal qualities and musical realism. The chip features extremely simple internal logic and does not manipulate the incoming digital data, allowing designers full control of the conversion process.

To elevate performance to extraordinary levels, the Ithaka employs twenty-four R2R converters per channel operating in parallel, for a total of forty-eight converters.

Paralleling converters significantly improves linearity and reduces noise while expanding dynamic range and channel separation. This architecture also minimizes the influence of resistor tolerance deviations, effectively averaging them across multiple networks and resulting in highly precise conversion accuracy.

Jitter Reduction and Clock Control

Precise timing is essential for accurate digital-to-analogue conversion. Even very small timing errors can degrade clarity and blur musical detail.

The Ithaka incorporates numerous passive and active techniques to suppress jitter throughout the digital signal path. Carefully engineered driver circuits and optimized digital signal terminations prevent signal reflections, overshoot, and other distortions that can lead to timing errors.

To further isolate digital circuits from power supply noise, the Ithaka employs an extensive filtering network consisting of seventy LC filters built from RF chokes and high-speed capacitors. These filters effectively block power supply interference from reaching the converter circuitry.

At the core of the timing architecture is the Aries Cerat Super Clock system. This precision clock directly drives the refresh signal for the R2R converter network, ensuring extremely accurate timing and conversion.

The Super Clock also reclocks incoming signals at the USB controller and S/PDIF receiver stages, synchronizing all data before it reaches the conversion stage. This internal clock architecture eliminates the need for an external word clock input while achieving jitter performance at the femtosecond level.

Transformer I/V Conversion

Because the R2R converter chips operate as current-output devices, their signal must be converted into voltage before it enters the analogue amplification stage.

Rather than relying on integrated operational amplifiers or simple resistor networks, the Ithaka uses a custom transformer-based current-to-voltage conversion stage. This transformer converts the differential current output into a single-ended voltage signal with exceptional linearity and bandwidth.

Transformer I/V conversion provides superior sonic transparency and dynamic capability, preserving the purity of the original signal while preparing it for amplification.

TriodeFet Output Stage

The defining element of the Ithaka design is its advanced analogue output stage, built around Aries Cerat’s third-generation TriodeFet technology.

This stage operates as a single-stage, single-ended Class A circuit with extremely wide bandwidth and exceptional linearity. The topology allows the qualities of the digital conversion stage to be transmitted with minimal alteration.

The output stage operates at a high idle current of one ampere and delivers an output impedance of only one ohm. This extremely low impedance gives the stage extraordinary drive capability and stability.

During development, the output stage proved powerful enough to drive loudspeakers directly, delivering up to twelve watts of output. While the Ithaka is not intended to function as a power amplifier, this capability demonstrates the remarkable strength and authority of its analogue output stage.

Power Supply Architecture

The Ithaka DAC is powered by an external power supply unit engineered to provide exceptionally clean and stable energy to every stage of the converter.

All digital and analogue circuits operate from independent low-impedance power supplies that use multiple cascaded filtering stages. High-quality inductors and capacitors remove both low-frequency and high-frequency noise from the power rails.

The TriodeFet stage is powered by a dedicated high-energy supply that uses a triple choke-filtered design capable of delivering substantial current with minimal noise.

Two low-noise 500VA toroidal transformers provide the primary power source for the system, feeding discrete Schottky silicon-carbide rectifiers known for their extremely low switching noise.

This comprehensive power architecture ensures that the digital conversion system and analogue stages operate under optimal electrical conditions at all times.

Technical Specifications

Digital Section

• Converter architecture
  24 R2R converters per channel using Analog Devices AD1865N-K chips (48 total)
• Current-to-voltage conversion
  Transformer I/V conversion with custom wideband transformers
• Clock system
  Internal Super Clock with triple regulated supply and quad-stage pre-filters
• Voltage regulation
  Eight discrete ultra-low-noise regulators for the converter banks

Power Supply Section

• Two low-noise 500VA toroidal transformers
• Over 4 Farads total system capacitance
• Extensive LC filtering and wideband decoupling
• Four independent pseudo-battery isolation systems
• Triple choke-filtered high-current power supply for the TriodeFet stage

Input & Output Section

• Gain stage
  Third-generation TriodeFet output stage operating in single-stage single-ended Class A topology
• Output range
  RCA: 30 Vpp output at 0 dB (10 Vrms)
• User selectable output tuning
  External resistive modules allow users to fine-tune output loading and sonic character
• Outputs
  2 × RCA
  2 × balanced XLR outputs
  True balanced architecture with floating RCA ground option
• Output impedance
  1 ohm
• Minimum output load
  3 ohms

Digital Inputs

USB input supporting up to 24-bit / 384 kHz

Additional inputs:

• AES/EBU
• S/PDIF
• BNC

Jitter attenuation
Down to femtosecond level

Physical Specifications

Dimensions
540 mm W × 580 mm D × 165 mm H

Weight
160 kg total unpacked

Source: https://aries-cerat.com/ianus-series-ithaka-digital-to-audio-converter/