Supreme 3 automatic fuse - 10.3 x 38 mm
Supreme 3 - Rev. 2.0 automatic fuse - 10.3 x 38 mm - 20 Amp - gg/gl - Hifi-Tuning

HiFi Mains Supply · Audiophile Fuses

“We hear the current from the wall socket” is an old HiFi truism. It originally meant that modern HiFi components reshape mains current to such a degree that the resulting waveform ultimately drives the loudspeakers — circuits, components and their dimensioning all have audible consequences for the final result. What the audio world largely ignored well into the early 21st century was the influence of the mains fuse on this same chain. Then a number of audiophiles noticed that simply swapping a fuse produced subtle but reproducible sonic changes. Today the fuse counts as one of the most cost-effective tuning measures in High End — and among the German pioneers, one name stands first: HiFi-Tuning Berlin.

Founder and sound tinkerer Bernd Ahne was one of the first in Germany to have fine fuses built consistently to audiophile criteria — by hand, in Berlin, following his own design philosophy: ceramic housings instead of glass, identical material for fuse wire and end caps, a mechanically damped fusible link, and cryogenic post-treatment for every finished fuse. The HiFi-Tuning Supreme³ Automatic Fuse 10.3 × 38 mm Silver/Copper is a special version of this line — built for use in fuse holders inside distribution boards, where the fuse acts most directly and most centrally on the power flow to the entire HiFi system.

Initially the topic of audiophile fuses was dismissed as wishful thinking. The turning point came with the publicly published observation that swapping a standard fine fuse for a high-quality one can significantly raise the damping factor of a transistor amplifier. With that, the electrical effect was suddenly measurable beyond the realm of pure listening — and the topic has since become a firmly established part of the HiFi world. HiFi magazines at home and abroad now unanimously recommend trying it; rarely can a comparable sonic gain be achieved with such a modest investment.

HiFi-Tuning Berlin today offers a complete range of audiophile fuses — all still hand-built in Germany. Bernd Ahne's design principles have been consistent since the first generation: ceramic housings instead of glass (greater mechanical stability, better thermal conductivity, none of the resonance behaviour of a glass cylinder), fuse wire and end caps from identical material (avoiding mismatches at the material boundaries), and a special coating that mechanically damps the fusible link itself. As a final step, every finished fuse passes through cryogenic treatment in Berlin — a controlled deep-cooling phase that stabilises the material structure and reduces internal resistance. Compared with industrial mass production, the HiFi-Tuning fuses measure a markedly lower internal resistance.

The Supreme³ Automatic Fuse offered here is a special version designed for use in fuse holders inside distribution boards. It comes in the standardised 10.3 × 38 mm format with a striking black ceramic body — visually a clear distinction from classic white industrial fuses and from the lighter ceramic bodies of the smaller fine fuses. The end caps are made of a silver-copper alloy and additionally plated with 24-karat gold. The gold layer is more than corrosion protection: it creates an electrically and mechanically defined contact surface to the fuse holder that does not deteriorate over years through micro-corrosion.

The choice of materials is a deliberately different concept from pure-copper fuses: silver has the highest electrical conductivity of any metal, copper ranks second. The alloy of both combines their strengths — the immediate energy and detail of silver with the natural tonal colour and substance of copper. Combined with the gold outer surface and the resonance-damping black ceramic body, the result is the balanced, dense and at the same time highly resolved sound that has made this fuse line one of the most successful tuning components for years.

Since April 2020, an improved version of the Supreme³ Automatic Fuse has been shipped — recognisable by the marking “Rev. 2.0” on the packaging. The central change: the fusible link now primarily consists of Cardas Grade 1 Copper. The change-over was so demanding that the supplier had to develop an entirely new manufacturing process — producing the finest copper wires with defined melting characteristics from a high-purity audio copper is anything but trivial.

Cardas Audio of the USA is regarded among audiophiles as one of the most respected copper specialists in the industry — Cardas OFC conductors can be found in the highest-quality speaker and interconnect cables of the trade. “Grade 1” denotes the highest purity and structural-quality grade in the Cardas internal classification. Having this material now form the fusible link of the Supreme³ is more than a marketing point — it is a consistent application of audiophile cable-making insights to the previously ignored fuse element. According to HiFi-Tuning, the Rev. 2.0 takes another small step beyond its already excellent predecessor.

The designation gg/gl is a standardised classification according to IEC 60269 describing the switching and protective behaviour of a low-voltage cartridge fuse. The first „g” stands for general purpose — the fuse is fully protective across the whole current range, from minor overcurrent up to short circuit. The second character indicates the protected object: „l” (for line) and „g” describe general line and installation protection. In practice this means: the fuse is suitable for the universal protection of wiring and residential distribution — exactly the application it is designed for.

The term “automatic fuse” is established in everyday language but technically a little misleading: a classical miniature circuit breaker (MCB) does not actually contain a fuse — it is an electromechanical protection device that can be reset. What this fuse actually goes into is a fuse holder in the same format as an MCB, mounted on the same DIN rail in the distribution board, accepting a cylindrical 10.3 × 38 mm fuse — the same form factor in the same location, but with a fusible insert instead of a switching mechanism.

Bernd Ahne explicitly recommends having a suitable fuse holder installed in the distribution board by your trusted electrician. The sonic improvements, according to HiFi-Tuning, are very clearly audible — and they act centrally on every HiFi component fed by the protected phase, without requiring any intervention on individual devices. This central effect is also why the automatic fuse, despite its unassuming appearance, enjoys such a strong reputation among audiophiles: a single measure — one fuse — affects the entire downstream chain.

Despite its audiophile optimisation, the Supreme³ is a fully compliant cartridge fuse: it conforms to IEC 60127-2 for fine fuse links and is CE-certified. It therefore meets the same safety requirements as a conventional cartridge fuse of identical form factor and current rating — the difference lies solely in the sonic optimisation of the internal construction, not in the protective functions.

Important: the fuse is installed in the residential distribution board, not inside individual HiFi components. For insurance and safety reasons, this work must always be carried out by a licensed electrician — both the replacement of the suitable fuse holder and the insertion of the fuse itself. Anyone preferring to operate the fuse at a more accessible location can have a corresponding 10.3 × 38 mm holder fitted in HiFi-Tuning's own design, mounted in an accessible enclosure as a pre-fuse for an individual distribution strip or a single device.