Description

Aries Cerat Kassandra Signature DAC

The Kassandra Signature DAC represents the ultimate evolution of the Kassandra digital conversion platform from Aries Cerat. Designed as a statement-level digital source, it builds upon the already exceptional Kassandra Reference architecture while pushing performance to even greater heights.

From the very beginning of Aries Cerat’s development, it was clear that creating world-class audio systems required a truly uncompromising source component. Loudspeakers, amplifiers, and preamplifiers can only reveal their full potential when fed by a digital source capable of extraordinary realism. The Kassandra platform was created to fulfill that role, delivering the tonal richness and musical flow of analogue sources while exceeding them in resolution, transparency, and dynamic capability.

The Kassandra Signature expands on this foundation with an advanced two-chassis architecture, separating the converter and power supply sections to further reduce interference and elevate overall performance.

Design Philosophy

The Kassandra Signature was developed as a direct evolution of the highly acclaimed Kassandra Reference DAC. The design team focused on refining every aspect of the converter system while incorporating design techniques used in other flagship Aries Cerat products.

Adopting a dual-chassis design — similar to the company’s Signature series amplifiers — provided additional space and electrical isolation for the power supply and digital circuitry. This approach allowed engineers to implement more advanced power supply technologies, many of which were inspired by the flagship Aries Cerat Impera Signature Preamplifier.

The result is a digital converter system that represents the limits of what is currently possible in digital-to-analogue reproduction.

R2R Ladder DAC Architecture

At the core of the Kassandra Signature is a true ladder DAC architecture, widely regarded by audiophiles as one of the most natural and musically convincing approaches to digital conversion.

A ladder DAC works by switching a precision resistor network according to the incoming digital data stream. This method allows the signal to be converted directly without complex digital manipulation.

The Kassandra Signature avoids common digital conversion approaches such as delta-sigma processing or multibit filtering, both of which can introduce sonic artifacts that affect natural timbre and musical flow.

Instead, Aries Cerat chose the classic Analog Devices AD1865N-K R2R converter chip. This legendary chip is widely respected for its simplicity and exceptionally musical sound characteristics.

To push performance to unprecedented levels, the Kassandra Signature uses twenty R2R converters per channel, arranged in parallel for a total of forty converters within the system.

Running converters in parallel offers several important benefits:

• Improved linearity

• Reduced noise and distortion

• Increased dynamic range

• Exceptional channel separation

By averaging resistor tolerances across multiple converter networks, this architecture achieves extremely precise signal conversion while delivering a richer and more natural sonic presentation.

Advanced Jitter Control

Accurate timing is essential in digital audio conversion. Even small timing errors can introduce distortion and degrade musical realism.

The Kassandra Signature employs a range of advanced techniques to minimize jitter throughout the digital signal path. Carefully designed driver circuits and precisely tuned digital line terminations eliminate signal reflections and overshoot that can lead to timing errors.

The system also incorporates 30 LC filters using RF chokes and high-speed capacitors to isolate digital circuits from power supply noise.

At the center of the clocking system is Aries Cerat’s proprietary Super Clock technology. This high-precision clock directly controls the refresh signal of the R2R converters, ensuring extremely accurate timing during the conversion process.

The Super Clock also reclocks the asynchronous USB controller and S/PDIF receiver, ensuring all incoming signals are synchronized with maximum precision. As a result, the Kassandra Signature achieves femtosecond-level jitter performance without requiring an external word clock.

Transformer I/V Conversion

Because the R2R converters operate in current output mode, the signal must be converted into voltage before it can enter the analogue stage.

Rather than using op-amps or simple resistor networks, Aries Cerat employs a custom transformer-based I/V conversion stage. This specially designed transformer converts the differential current output into a single-ended voltage signal while preserving signal purity and dynamic capability.

Compared with traditional I/V conversion methods, transformer conversion offers exceptional transparency and musical realism.

Tube Output Stage

Following the I/V stage, the signal enters a single-ended tube amplification stage derived from Aries Cerat’s amplifier and preamplifier designs.

The stage uses the renowned E280F super tube, connected in triode configuration for optimal linearity and low noise performance. This tube is highly regarded for its excellent transconductance and extremely stable operating characteristics.

The triode stage is loaded by a large-core step-down transformer and powered by an oversized choke-regulated power supply, allowing the circuit to respond effortlessly to wide dynamic swings in the music signal.

This transformer coupling also lowers output impedance to approximately 40 ohms, ensuring excellent compatibility with downstream components.

Power Supply Architecture

The Kassandra Signature employs one of the most sophisticated power supply systems ever implemented in a DAC.

Key features include:

• Four large toroidal transformers
• More than 2 Farads of total system capacitance
• Extensive local decoupling using 76 tuned LC filters
• A pseudo-battery system isolating analogue circuits from the power grid
• Xenon gas rectifiers used in the tube power supply

This massive and carefully engineered power supply ensures exceptional stability and extremely low noise levels throughout the system.

Technical Specifications

Digital Section

• Converter architecture:
  20 R2R converters per channel using Analog Devices AD1865N-K chips (40 total)
• Current-to-voltage conversion:
  Custom transformer I/V stage with balanced current to single-ended voltage conversion
• Clock system:
  Internal Super Clock with triple regulated power supply
• Voltage regulation:
  Eight discrete ultra-low-noise regulators for the converter banks

Power Supply Section

• Four toroidal transformers
• Over 2 Farads of total system capacitance
• Extensive LC filtering (76 filters)
• Pseudo-battery system for analog stage isolation
• Xenon gas rectifiers for tube power supply

Input & Output Section

• Gain stage:
  Transformer-loaded tube output stage using E280F tube
  5:1 / 10:1 step-down transformer with double choke filtered supply
• Output range:
  RCA: 30 Vpp output at 0 dB (10 Vrms)
  5 Vrms output at −6 dB setting
• User selectable output:
  10 V @ 50 ohms
  5 V @ 12 ohms
• Outputs:
  2 × RCA
  2 × Balanced XLR
  True balanced output architecture

Floating RCA output switchable for ground loop resolution

• Output impedance:
  50 ohms (balanced and single-ended)
  12 ohms at −6 dB setting

Digital Inputs

USB input supporting up to 24-bit / 384 kHz

Additional inputs:
AES/EBU, S/PDIF, BNC (others available on request)

Jitter attenuation:
Down to femtosecond levels

Physical Specifications

Dimensions:
540 mm (W) × 350 mm (D) × 165 mm (H)

Weight:
80 kg total

Source: https://aries-cerat.com/kassandra-signature-product-page/