Technique

Energy-domain foundations and circuit behaviour

Within an electroacoustic reproduction chain, the power-supply system is the point at which electrical energy is made available to the circuits that process, control or amplify the signal.

The power supply is therefore not merely an auxiliary function: it contributes to defining the physical conditions within which the active stages of the reproduction chain operate. Variations in voltage, impedance, noise, coupling or recovery can alter those operating conditions and, when sufficiently significant, interact with circuit behaviour.

Energy-domain stability must therefore be considered in relation to load, level, duration, frequency and system state, rather than solely through nominal values of power or delivery capability.

The power-supply system thus constitutes the interface through which the mains supply, available energy and circuit behaviour enter into relation within the electroacoustic chain.

Mains-frequency power supplies and energy-domain behaviour

For many decades, power supplies based on transformers operating at mains frequency have represented a widely used solution in audio electronics. Considered from the standpoint of energy-domain behaviour, they exhibit specific characteristics and constraints associated with 50/60 Hz transformation, rectification, energy storage and release, and the properties of magnetic materials.

Architectures comprising a mains transformer, rectifier and capacitive smoothing are commonly classified as “linear” power supplies, in contrast with switch-mode power supplies. The designation is purely conventional and does not imply that magnetic transformation, rectification, capacitor charging and load response are perfectly linear processes.

A characteristic component of these architectures is residual ripple. In a typical full-wave rectified architecture, the transformer supplies an alternating voltage at mains frequency, the rectifier converts it into a pulsating voltage, and the filter capacitors charge near the peaks before releasing energy to the load between successive peaks.

The resulting DC voltage may therefore contain a residual AC component, typically at 100 or 120 Hz, together with other components dependent upon the architecture and operating conditions. Filtering and regulation can reduce its magnitude substantially, but the relevance of the phenomenon must be assessed in the actual system and under the operating conditions considered.

The power-supply domain should therefore not be represented as an ideal, infinite or immutable source, but as a physical system possessing impedance, noise, dynamic limits, energy-storage capability, and finite release and recovery times.

Energy modulation, hysteresis and circuit behaviour

Ripple, when sufficiently contained, may not exert a determining influence. Variations in supply voltage and source impedance can nevertheless interact with the currents demanded by the circuits, particularly in the presence of dynamic signals and variable loads.

Depending on the architecture, relevant phenomena include: variations in ground-reference conditions; variations in bias points; interaction between power-supply impedance and dynamic current demand; and coupling between channels or stages through shared energy domains and return paths.

A further consideration is hysteresis in magnetic materials. In such systems, the present response may, under defined conditions, depend on the preceding state of the magnetic circuit and therefore on the recent magnetisation history of the core. In the 'AURORA' Lexicon, this and other dependencies upon a preceding state fall within the descriptive class of “energy memory”. Energy memory does not designate an autonomous physical mechanism, nor does it imply an intrinsically adverse effect; it can, however, become structurally relevant when it introduces asynchronous contributions or variations in gain, phase, noise or recovery that are incompatible with the reference representation.

Energy storage and release in capacitors are likewise normal and necessary processes in the operation of a power supply. They become structurally relevant when, under the conditions considered, they contribute to voltage variations, recovery times, modulation or coupling capable of materially altering circuit behaviour.

Verification of these phenomena therefore requires dynamic measurements and representative test conditions; it cannot be inferred from the mere presence of a particular topology or category of component.

Mechanical and magnetic effects

Transformer-based power supplies can also introduce secondary physical phenomena.

Magnetostriction of the core can generate mechanical vibration, while stray magnetic fields can couple into surrounding circuitry. The magnitude of these effects depends upon the component, load, physical arrangement, separation distances, shielding and coupling paths present within the system.

Careful design can reduce these phenomena to the point at which they are not significant under the conditions considered. Their relevance must therefore be established in the context of the actual implementation.

The Black Cosmic Space™ research framework

Black Cosmic Space™ identifies an SMPS power-supply architecture and the associated research and design framework developed within AURORA Electron Devices® to investigate and control the influence of the power-supply domain upon circuit operating conditions, with particular attention to noise, dynamic impedance, recovery, separation of energy domains and dependencies upon temporally preceding energetic states.

Work undertaken within this field has explored high-frequency resonant SMPS topologies, dedicated filtering, controlled grounding, functional separation, and the reduction of mechanical and magnetic perturbations.

The technical objectives of the research framework include:

• containment of residual noise;
• reduction of dynamic impedance under the intended operating conditions;
• high independence between channels and energy domains where required by the architecture;
• containment of mechanical and magnetic perturbations;
• predictable voltage and current behaviour in relation to load and signal dynamics;
• control of recovery phenomena and dependencies upon the system’s energy history.

Black Cosmic Space™ was developed to investigate and contain, within defined conditions, certain limitations characteristic of conventional power-supply architectures applied to audio circuitry, adopting an assessment criterion directed towards controlling and measuring behaviour under real operating conditions and within pre-established and defined design limits.

Topologies and configurations for investigation

Black Cosmic Space™ does not correspond to a single mandatory circuit configuration. It defines a set of technical criteria whose application depends upon circuit function, load, control objectives and the operating conditions under investigation.

Among the configurations investigated in the 'AURORA' design programme is true dual mono, adopted where consistent with the objective of increasing channel independence and separating the respective energy paths.

The same principle applies to dedicated high-frequency filtering, grounding, separation of energy domains, control of return paths and reduction of dynamic impedance: these are design instruments that can be combined in different forms, and whose effectiveness must be verified through explicit physical quantities and protocols compatible with the actual behaviour of the circuit.

Stability of energetic potential

In the terminology of the 'AURORA' Lexicon, “stability of energetic potential” describes the ability of a section of the chain to make voltage and current available under the intended conditions while keeping under control variations in impedance, temperature, noise and recovery that may alter the signal. The expression does not designate an autonomous physical quantity distinct from the measurable quantities that determine it.

The term therefore does not imply an ideal, infinite or immobile source. Every power supply possesses resistance, reactance, noise, limits and state dynamics. Stability is relative to load, level, duration, frequency and system state.

When these conditions are adequately controlled:

• modulation originating within the power-supply domain may be reduced;
• reference conditions may become more stable;
• response to transient demands may become more predictable;
• coupling between channels or stages may decrease;
• unwanted dependencies upon the preceding energetic state may be contained.

These outcomes must be verified experimentally under the operating conditions considered and not inferred from the power-supply schematic alone.

Within the framework of the Theory of Pattern Conservation in Stereophonic Electroacoustic Reproduction, the power-supply domain constitutes one of the physical conditions that can contribute to the preservation or degradation of the structural relationships represented by the reference pattern.

The pattern does not coincide with the total quantity of energy: it is represented by the organisation of modulations and relationships between the pertinent physical quantities. Reducing noise, self-generated modulation, coupling, uncontrolled recovery or history dependence can therefore contribute to limiting a class of perturbations introduced within the energy domain.

Such a contribution does not, by itself, demonstrate pattern conservation throughout the entire chain. Each stage of reading or reception, conversion, processing, amplification, transduction, radiation and propagation must be considered within its own domain and conditions of validity.

From this perspective, Black Cosmic Space™ confines its field of research to the behaviour of the power-supply domain and its interactions with the circuitry, without assigning to energy architecture alone a universal function of pattern conservation.

Energy conditions and auditory perception

The perceptual consequences of a difference in the power-supply domain cannot be inferred automatically from the topology adopted. They must, wherever possible, be related to repeatable physical differences and assessed under controlled listening conditions.

When variations in noise, impedance, coupling, recovery or preceding energetic state become sufficient to alter the behaviour of the chain, any perceptual differences may be described in terms of greater or lesser transient definition, intelligibility of low-level information, stability of spatial cues, dynamic articulation or localisation.

Such descriptions belong to the perceptual level and do not automatically identify a single physical parameter. Their interpretation therefore requires correlation with measurements, control of conditions, and distinction from expectation effects, thermal drift or other unrelated variables.

The expression “black background”, recurrent in listening descriptions, may denote a perception of lower noise, reduced masking or greater intelligibility of weak information. It does not, however, constitute an autonomous physical quantity and, by itself, does not demonstrate that the cause is a specific reduction in energy modulation or system memory.

Within the 'AURORA' framework, the value of a perceptual observation therefore lies in the possibility of relating it to repeatable differences in the system and, wherever possible, to an identifiable physical correlate.

Historical implementations and research applications

Black Cosmic Space™ has been studied and experimentally investigated through different design approaches, with configurations adapted to the circuit function and operating conditions considered.

The solutions investigated have included, as appropriate, separation of energy domains, dual-mono configurations, dedicated filtering, management of ground and return paths, noise control, reduction of dynamic impedance, and attention to energy-storage and recovery phenomena, with the objective of establishing under which conditions management of the energy domain can reduce perturbations uncorrelated with the structure of the signal.

Conclusions

A sufficiently stable and predictable energy domain can reduce the influence of noise, self-generated modulation, coupling, recovery phenomena and dependencies upon temporally preceding operating states on the operating conditions of the circuitry.

The relevance of these phenomena must nevertheless be established case by case through explicit measurements, dynamic signals, representative loads and, where pertinent, controlled listening protocols.

Within the 'AURORA' research framework, Black Cosmic Space™ identifies an approach developed to investigate these conditions through power-supply architecture, energy distribution, filtering, functional separation and control of mechanisms dependent upon dynamic-temporal history.

Its purpose is not to impose a character upon the signal, but to investigate and contain a class of physical conditions which, when sufficiently significant, can alter its representation within the chain.

Within the framework of the Theory of Pattern Conservation, this work therefore addresses a defined part of the general problem: control of the structural consequences of the transfer, storage, conversion and release of energy within the power-supply domain.