Supreme 4 OCC-AgAu1 automatic circuit breaker - 10.3 x 38 mm
- 16 Amp

Power Supply · Audiophile Fuses

Every ampere of current that reaches a hi-fi system first passes through a fuse. What is intended as a humble protective component therefore sits at one of the most delicate points in the signal chain: a thin fusible wire, a handful of grain boundaries within the metal, one contact too many — and the current loses its purity before it ever arrives at the power supply. This is precisely where HiFi-Tuning of Berlin has been working for years. With the new Supreme⁴ OCC-AgAu1, sound engineer Bernd Ahne now presents the long-awaited successor to his bestselling cabinet fuse — pushing conductivity a further, clearly audible step forward: more dynamics, finer resolution, greater spatiality and naturalness.

The difference comes down to a newly developed fusible conductor. The designation “AgAu1” reveals the recipe: a monocrystalline silver-gold alloy of 99 % silver and 1 % gold — according to the manufacturer, the world's first fuse element of its kind. Silver is the finest electrical conductor of all, yet in pure form it tends to tarnish; the minimal gold content stabilises the material against corrosion and ageing without meaningfully reducing its conductivity. The decisive factor is the monocrystalline structure produced by the OCC process (Ohno Continuous Casting): instead of countless short crystals with just as many grain boundaries, the metal grows into long, continuous single crystals. The current need not cross a multitude of crystal junctions — each of which is a tiny resistance and a potential source of distortion.

HiFi-Tuning follows a design philosophy that sets it firmly apart from mass-produced industrial goods. The housing is made of black ceramic rather than glass — ceramic is mechanically more robust, damps its own resonances more effectively and contains the arc more safely when the fuse blows. The end caps are crafted from the finest silver-plated OFC copper and then given a wafer-thin layer of 24-carat gold, which permanently protects the contact surfaces from oxidation and keeps contact resistance low. The fact that both conductor and terminals are made of consistently noble, low-oxygen materials lowers the fuse's internal resistance appreciably below that of conventional protective components.

Each fuse receives its finishing touch through a cryogenic treatment: the completed component is deep-cooled for a full week in a computer-controlled process at −196 °C — the boiling point of liquid nitrogen. This sub-zero treatment relaxes the metal's microstructure, homogenises the crystal lattice and reduces microscopic stresses within the conductor material. The result is a measurably more uniform current flow and a further reduction in internal resistance. Each Supreme⁴ is then made by hand in Germany, packaged individually and tested in line with the international safety standard UL248.

A fuse produces no sound of its own — but it can curtail it. Every needless resistance, every grain boundary and every poor contact acts like a fine filter, drawing energy and information from the current before it reaches the power supply. This is exactly what the Supreme⁴ addresses: thanks to the monocrystalline silver-gold conductor, the noble contact surfaces and the cryogenic refinement, the current arrives at the component more cleanly and unimpeded. The result is audible as a quieter background from which the finest details emerge more distinctly — the famous “black silence” between the notes.

Compared with the already excellent Supreme³ predecessor, listeners report above all greater dynamics, fine resolution and spatiality: instruments become more precisely placeable, the soundstage opens up, and the entire presentation feels more natural and effortless. Swapping in an audiophile fuse is thus one of the most inconspicuous yet most fundamental interventions one can make to a system — it works at the very root of the signal chain, at the power supply itself.

The Supreme⁴ OCC-AgAu1 measures 10.3 × 38 mm and is therefore designed for use in the typical cylindrical fuse holders of electrical cabinets. The label “automatic fuse” is somewhat misleading: this is a high-quality fusible link inserted into a corresponding cabinet-mounted fuse holder. For the best sonic result, Bernd Ahne expressly recommends using a suitable, high-quality fuse holder — since its contact quality, too, has a bearing on the final outcome.

Those seeking the very maximum will find the Supreme⁴ additionally available in a “Diamond” version (diamond diameter 2 mm). It is technically identical in construction, yet the gains in sonic quality are once again clearly audible. Both versions are initially offered as a 16-ampere variant.

Important note: The installation of an automatic fuse, and all work on electrical installations, must be carried out exclusively by a qualified specialist. Please also bear in mind that audiophile fuses across all brands have a very low tripping tolerance. In devices with high inrush currents (such as those from Naim or Accuphase), the fuse may in rare cases trip on the very first switch-on. When in doubt, please confirm the rating with the device manufacturer.