The Evolution of My Digital Devices

My journey into building external digital converters began in the 1990s. Inspired by Peter Qvortrup’s article Time Waits for No-One…, my search soon focused on multibit DAC chips, transformer coupling, non-oversampling (NOS) mode, and tube output stages—though there were occasional deviations along the way. Out of curiosity, I tested all known digital filters, only to find that nearly all of them led to a significant deterioration in sound quality. The sole exception was the SAA7030 when paired with the TDA1540.

Every other digital filter altered the sonic landscape in ways that merely replaced one set of flaws with another, often less tolerable. For many years, I improved the output stage and transformers, believing them to be the primary influences on sound quality. However, a realization dawned on me: the true determinant of digital audio performance extends far beyond the output stage and current- voltage conversion method. The power supply plays a far greater role.

The impact of power supply design is not limited to the type of voltage regulators used. It encompasses every aspect: decoupling and filtering capacitors, transformer materials and their physical arrangement, the phasing of windings, rectifier topology, diode selection, and transistor choice. While excellent solutions for output stages have long been available, power supplies have remained largely neglected. Even in high-end digital equipment, high-quality  diodes, transistors and voltage stabilizers are rare.

It should come as no surprise that commonly used voltage regulator chips such as LM317, 7805, and 7905 severely limit audio performance. Whether the problem lies in circuit complexity, negative feedback, or material quality is a matter for speculation. Personally, I prefer to focus on results rather than theorizing over their causes—life is too short for both.

Since my first use of a shunt voltage regulator based on germanium transistors in the late 1990s, I recognized a path few had explored. The improvement in digital music reproduction was striking. Yet, over time, I discovered that shunt regulators alone were not sufficient. They excelled in certain areas but had limitations in others. The best approach, I found, was a combination of different stabilizer types, each chosen for its specific strengths. While many who copy my designs rely solely on shunt regulators, my latest work incorporates four distinct types, some featuring entirely novel solutions.

Beyond regulators, every component before them—the power transformer and rectifier—is of crucial importance. For most circuits, I favor a half-wave rectifier, though I use a full-wave design for the output stage. Half-wave rectification has inherent limitations and cannot be universally applied.

My approach to current-to-voltage conversion has also evolved. Several years ago, I moved away from using transformers in this section, as I achieved superior results with a germanium transistor-based converter. This circuit has undergone significant development, progressing from a simple NPN design with a single-polarity power supply to a more advanced PNP structure requiring both positive and negative voltages—sometimes even with tube rectification. I now use high-frequency transistors, carefully selecting different types to match various DAC chips, allowing me to highlight their best qualities and achieve a more harmonious overall performance.

The question of transformer use in audio remains a complex one. High-quality transformers can indeed provide excellent sound, but they inevitably introduce distortions that I now find unacceptable. My goal is to extract the maximum musicality , beauty and informativeness without imposing bandwidth limitations, extra coloration, or dynamic compression. A transformer at the DAC output inevitably restricts dynamic peaks—this is a fundamental law of physics. The perceived warmth of transformers is often due more to the sheer quantity of copper used than to the method of signal transfer itself. Greater sonic benefits can be realized through alternatives such as chokes, autotransformers, and wire-wound copper resistors.

There are, however, two applications where classic transformers remain indispensable: step-up transformers for moving coil (MC) cartridges and step-down output transformers in tube amplifiers. Beyond these, transformers function as little more than additional filters—akin to tinted lenses designed to mask a system’s underlying deficiencies. My pursuit remains the same: to refine every element of the circuit, ensuring that music is reproduced with the greatest possible clarity, depth, and realism.

Advancements in I/U Conversion and the Birth of New DAC Models

Regarding the current-to-voltage (I/U) converter based on germanium transistors, my experience has confirmed that this approach offers the highest linearity, the best dynamics, the widest soundstage, and the most precise instrument localization. A converter with exceptionally low input resistance (less than 3 ohms) creates ideal working conditions for the DAC chip’s output stage—something neither a resistor nor a transformer can achieve. However, its apparent simplicity is deceptive; such a converter can only deliver superior sound quality when meticulously designed, with carefully selected components and a properly structured power supply. Over many years, I have refined this approach until I was fully satisfied with the results.

The Emergence of New Devices

Following the principles outlined above, two new DAC models have been developed: Psyche and Hermes.

• Psyche is based on the renowned TDA1541 chip.
• Hermes is a more versatile design, accommodating up to four interchangeable modules, allowing it to support different DAC chips: PCM58, PCM63, AD1865 (1864), and AD1862.

Each chip has its own dedicated module. Three of these modules can be swapped without requiring circuit modifications. However, the PCM58 module necessitates an adjustment to one of the voltage regulators, which should be taken into account when placing pre-orders.

These DACs incorporate the finest solutions developed in recent years: tube rectifiers in the DAC power supply, a combination of different stabilizer types tailored to specific circuit requirements, a balanced input, and the option for balanced output.

The Signature versions also feature my handcrafted capacitors and resistors, further enhancing their sonic performance.

In the following articles, I will provide a detailed look at each model, exploring their unique design elements and sonic characteristics.