Description

Aries Cerat Kassandra Reference DAC

The Kassandra Reference DAC represents the pursuit of a truly uncompromised digital source. Designed as part of the flagship Reference Series from Aries Cerat, it was created with a clear goal: to build a digital converter capable of delivering the natural timbre, flow, and musicality of the finest analogue sources while surpassing them in resolution and dynamic presentation.

From the earliest stages of developing the Aries Cerat reference system, it became clear that a true state-of-the-art source component was essential. Designing world-class loudspeakers and amplifiers demands a source that can reveal the full potential of the system. The Kassandra DAC was developed to fulfill that role — a reference-grade digital source built without compromise.

Design Philosophy

The development of the Kassandra began with a complete re-evaluation of existing DAC designs. Extensive listening tests and technical analysis showed that many digital converters on the market share similar limitations: a certain sonic character, reduced dynamics, and a lack of the natural tonal flow associated with high-quality analogue playback.

While developing the Aries Cerat reference system, numerous DAC designs were evaluated, yet none delivered the level of realism and musicality required. Both Delta-Sigma and multibit converter architectures were examined but ultimately did not achieve the analogue-like sound quality that Aries Cerat aimed for.

This led to the adoption of a pure R2R ladder DAC architecture, which provided the most direct and natural approach to digital conversion. The result was the development of the proprietary digital engine used in the Kassandra series, based on the renowned AD1865N-K converter chip.

R2R Ladder DAC Architecture

The Kassandra Reference DAC is built around a true ladder DAC architecture, a design that uses a precision resistor network controlled by digital switching. In this approach, the incoming data stream directly controls the resistor ladder, converting the digital signal to analogue voltage without manipulation or complex processing. Unlike many modern converters, the Kassandra uses no digital filters and no delta-sigma processing, avoiding the sonic artifacts that can arise from those architectures.

At the core of the converter are the classic AD1865N-K R2R chips, widely respected for their straightforward data handling and exceptionally musical sound. Their simple architecture allows the data stream to be handled directly without additional processing stages.

To maximize performance, the Kassandra employs sixteen R2R converters per channel arranged in parallel. This configuration dramatically improves linearity while reducing noise and distortion. By paralleling converters, resistor tolerances effectively cancel out, producing extremely precise conversion and exceptional dynamic range. Beyond the technical advantages, this design elevates sonic performance across the board, improving tonal density, channel separation, and micro-dynamic resolution — all critical elements for high-end audio reproduction.

Jitter Control and Super Clock Technology

Precise timing is essential for accurate digital conversion. The Kassandra Reference DAC uses a number of advanced techniques to minimize jitter at every stage of the signal path. Specialized driver circuits and carefully tuned digital line terminations ensure stable signal transmission and prevent timing errors caused by signal reflections or overshoot. Additionally, the digital circuitry is isolated from power supply interference through an extensive filtering network consisting of 35 LC filters using RF chokes and high-speed capacitors.

At the heart of the timing system is Aries Cerat’s proprietary Super Clock technology. This high-precision clock directly controls the refresh signal of the R2R converters, eliminating jitter before it can affect the conversion process. The Super Clock is also used to reclock the asynchronous USB interface and S/PDIF receiver, ensuring that incoming data is synchronized with extreme accuracy. With this internal clocking architecture, an external word clock input is unnecessary. The result is a conversion system capable of femtosecond-level jitter performance, allowing the Kassandra to deliver extraordinary clarity and precision.

Transformer I/V Conversion

Because the R2R converters operate in current output mode, the signal must be converted into voltage before entering the analog stage. Instead of using conventional 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 the purity of the original signal. Compared to other I/V methods, this approach offers superior sonic transparency and dynamic capability.

Tube Gain Stage

Following the I/V conversion stage, the analog signal is amplified by a single-ended tube gain stage derived from Aries Cerat’s world-class amplifier designs. The stage uses the highly regarded E280F super tube, connected in triode configuration. This tube is known for its exceptional linearity, low noise, and high transconductance, making it ideal for precision audio applications.

The tube is loaded by a large-core step-down output transformer and powered by an oversized choke-regulated power supply. This ensures the analog stage can respond instantly to the converter’s wide dynamic range while maintaining extremely low noise levels. The step-down transformer also reduces output impedance to approximately 40 ohms, enabling strong drive capability and excellent system compatibility.

Technical Specifications

Digital Section

• Converter Architecture
  16 R2R converters per channel using Analog Devices AD1865N-K chips
  Eight converters per bank, two banks per channel
• Voltage Regulation
  Eight discrete ultra-low-noise regulators for the converter banks
• Power Supply
  Over-engineered power supply with extensive input filtering
• Current-to-Voltage Conversion
  Custom wideband transformer I/V conversion
  Balanced current to single-ended voltage conversion
• Clock System
  Internal Super Clock with triple regulated supply
  Clock bypass selectable on the fly

Input & Output Section

Power Supply
Large toroidal transformer with oversized capacitor banks and input filtering

Analog Gain Stage
Transformer-loaded tube output stage using the E280F super tube
5:1 / 10:1 step-down transformer
Double choke filtered power supply

Outputs

Output range: 30 Vpp at 0 dB (10 Vrms)
5 Vrms output at −6 dB setting

User selectable output levels:
10 V @ 50 ohms
5 V @ 12 ohms

2 × RCA outputs
2 × Balanced (XLR) outputs
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

Jitter attenuation down to femtosecond levels

Physical Specifications

Dimensions:
540 mm (W) × 520 mm (D) × 165 mm (H)

Weight:
60 kg

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