As everyone knows, not just guessed, but clearly understood, just like in other areas of human activity, the broader audio field easily finds brands that almost universally emphasize their uniqueness, exclusivity, and high-end status—in layman’s terms, those eager for quick success, flaunting their achievements on display walls; and simultaneously, those brands that don’t need to prove anything to anyone, simply doing what they’re supposed to do, not deliberately chasing spotlights or industry magazine covers. I have no intention of judging which of these business models is correct, so I’m only mentioning it out of a purely record-keeping obligation. Our protagonist today belongs to the latter camp. Therefore, it doesn’t occupy full-page ads in magazines, nor does it rely on a large number of blindly loyal followers fighting for its reputation; instead, it focuses on what it does best, a point we’ll discuss shortly, leaving the evaluation of its performance to the users. Here’s an interesting point: its product portfolio includes both accessible budget-friendly options and choices for the most discerning audiophiles seeking refined sound. Who and what are we talking about? This is the German brand in-akustik, known for its incredibly diverse product portfolio. Thanks to the generosity of Horn in Warsaw, we were able to test a very beautiful (and, to give you a little spoiler, that’s not its only advantage)… power cord: the Referenz AC-2405 AIR.

The Referenz AC-2405 AIR is in-akustik’s second-highest-end power cord, only below the flagship AC-4005 AIR, in terms of diameter (25 pairs, 40 mm), number of conductors (4 pairs, 16), total diameter (2 x 3 mm² to 2 x 4 mm²), and, predictably… price. However, the rest is commonplace. First and foremost, what catches the eye, or more accurately, is its “accessibility”—despite the aforementioned 25 mm diameter, in-akustik’s cable is remarkably soft, almost “flowing.” This ergonomically appealing feature is thanks to its unique structure, which allows it to be seen and even touched through the perforated outer mesh. But let’s start from the beginning: the appearance. It’s remarkably elegant, possessing a captivating ethereal beauty due to its exquisitely anatomically designed structure. The outer sheath is a semi-transparent layer, unlike its sister models, the LS-2404 and LS-4004 speaker wires. Instead of white, it’s a black “skin,” beneath which lies the shielding layer—a dense tinned copper braid tightly wrapping plastic “rings”—special conductor clamps used to maintain the required geometry for the conductors passing through. The frosted aluminum tubing serves not only a decorative purpose but also an informational and practical function. It reduces the wire diameter before the delicate carbon fiber connector and indicates the manufacturer, model, serial number, and… the intended use of this sample. It’s also worth mentioning that the 2405 is available both as a “bare wire” version—with only finished ends—and as a version with configured C15 and C19 plugs. This clearly indicates its ability to handle high-power amplifiers (such as our editorial team’s Gryphon Apex) and power processors (such as the same manufacturer’s Reference Power Station AC-4500 Full 6F, or Keces BP-5000) equipped with such sockets.

As for the internal structure, four high-purity, 1.5 mm² multi-core copper conductors are wired within the conductor frame clamps—forming a hinged “clamp” skeleton—using the patented AIR Helix Point-to-Point fifth-generation technology. The primary insulation is air, a medium that eliminates the need for other materials that might absorb the conductor’s energy transmission like a sponge. A fifth PE (ground) conductor runs through the center; although the manufacturer carefully omits this fact, it can be assumed to have the same diameter as its surrounding conductors.

Moving on to the listening experience description from the test, I’d like to add some explanation. Since I’m unsure about the timeframe used to provide the test sample, and knowing the manufacturer recommends a burn-in period of 20-50 hours, I gave the in-akustik cable in my system the first few days to “stretch its muscles” and adapt. As you might guess, this adaptation period also applied to me, aiming to eliminate the influence of initial excitement as effectively as possible. Yes, when this German cable connecting the amplifier to the wall reached its expected stable state, and I stopped glancing at it every now and then, wondering whether it was time to wait, things became clear: the Referenz AC-2405 AIR’s advantage lies not only in its exceptional ergonomics and timeless design, but also in its sound performance. Because it represents a very elite group of cables that discreetly retreat into the background, allowing the music to flow at its own pace, whatever that pace may be. Strange? Or rather, it’s only natural? Not necessarily. You’ve undoubtedly encountered cables on your audiophile journey that “improve” certain aspects, elevating a specific performance level to near-stratospheric levels, leaving you speechless or prompting a few trendy, emphatic pronouncements of admiration. However, according to its creators, in-akustik doesn’t improve anything—because the original cannot be improved—but rather minimizes the damage. Yes, my dear audiophile readers, let’s be clear: the Germans, with their innate gentleness and refinement (after all, how sweet and poetic the innocent “butterfly” sounds in Goethe’s language), acknowledge that every connection, including power connections, is lossy. Therefore, the primary goal is to achieve zero-delay power delivery, minimal loss, and in the shortest possible time. And the cable in the title “plays” losslessly in this way, thus providing an argument for those stubborn cable skeptics who stubbornly believe “cables have no sound.” The key is that this “silence” isn’t a characteristic of “desk lamp cords” or “computer cables,” but rather a characteristic of high-end cables in the strictest sense, a category our customers undoubtedly fall into. It’s roughly like living in the illusion that money can’t buy happiness, while simultaneously representing so-called “old money” families. In these families, this wealth, if not from the beginning, has been passed down for at least several generations.

Seriously speaking, the AC-2405 AIR offers an extremely balanced and natural sound, allowing you to fully understand the recording content, not by emphasizing individual components through auditory impact, but by presenting the clarity, resolution, and stability of the sound source within the soundstage. This allows listeners to freely explore the recording once interested, without worrying about encountering rounded, blurry extras like Moomin behind the front-line, magazine-cut, laser-precise and sharp-edged characters. This applies not only to small, chamber ensembles (Tormod Dalen, Hans Knut Sveen, and Sigurd Imsen’s “TARTINI Secondo Natura” trio) but also to large performances (Stokowski’s “Rhapsodies”). In the latter, you can hear and feel firsthand that true dynamics are not about artificially speeding up the tempo and tense volume jumps, but about the ability to control everything on stage with Stoic composure, from whisper-level to jet-roar-level volume, and the ability to switch instantaneously between different states. With in-akustik’s involvement, various types of roughness and near-garage-recording grime are also very successfully achieved. Therefore, when using it in the signal path, you can freely engage with the sharp, unforgiving torrent of metal, like Metallica’s “Garage Inc.”, or the raw blues (Tony Joe White’s “The Heroines”). Just remember that this German cable itself doesn’t add any extra graininess or rusty roughness; if anything, it also ensures that no dirt will tarnish the unfathomable background of velvet black. Thus, compared to some more expressive “cables,” the in-akustik might, at least initially, be considered too conventional and neat—a mistake, and a fleeting one. Because making playback dull and smooth is one thing (the AC-2405 AIR doesn’t do that), but ensuring that only useful signals are processed—that is, the signals present in the recording—are not tainted by parasitic noise, which is precisely the pinnacle of Referenz’s perfection. Therefore, only those who genuinely appreciate the dry, peppery cymbals, the crisp, palmier drumbeats, and the jarring, improvisational repetitions might find our guests today lacking in the rawness of a far from reference-quality release like Iron Maiden’s “Best Of The B-Sides.” Well, since this is still a free country, everyone has the right to their own opinion, and I strongly encourage you to verify and form your own judgment. As for me and my ears, the 2405 may not be “ear-pulling” in its presentation (after all, the album is part of the “Eddie’s Archive” set), but it also doesn’t bear the aforementioned rawness, making even hours of listening entirely possible, and even recommended for fans of the genre.

In short, let me assert that the in-akustik Referenz AC-2405 AIR is, on the one hand, a thoroughly high-end power cord due to its “lossless” nature, and on the other hand, extremely “safe.” Because its presence neither alters the tonal balance of connected equipment nor emphasizes or highlights any unpredictable frequency components, but merely unleashes the potential within the equipment and facilitates the flow of its vital energy. Furthermore, it performs excellently with a wide range of power, from high-powered transistor amplifiers to much smaller tube amplifiers of a few watts, or even with a source unit. Therefore, potential buyers don’t need to consider whether it can be used throughout their existing system during future system adjustments, or whether it’s limited to a specific, dedicated purpose.

The system used for testing:

– CD/DAC: Vitus Audio SCD-025 Mk.II + 2 x Quantum Science Audio (QSA) Blue fuses

– Streaming player: Lumïn U2 Mini + Farad Super3 + Farad DC Level 2 copper DC cable + Omicron Magic Dream Classic; I-O Data Soundgenic HDL-RA4TB

– Turntable: Denon DP-3000NE + Denon DL-103R

– Phono preamp: Tellurium Q Iridium MM/MC Phono Pre Amp

– Digital source selector: Audio Authority 1177

– Integrated amplifier: Vitus Audio RI-101 MkII + Quantum Science Audio (QSA) Violet fuses

– Speakers: Dynaudio Contour 30 + Acoustic Revive SPU-8 pads + Base Audio quartz platform; AudioSolutions Figaro L2

– RCA Signal cables: Furutech FA-13S; NEO d+ RCA Class B Stereo + Ground (1m) phono amplifier cable

– XLR signal cables: Vermöuth Audio Reference; Furutech DAS-4.1

– Digital cables: Fadel art DigiLitz; Harmonic Technology Cyberlink Copper; Apogee Wyde Eye; Monster Cable Interlink LightSpeed ​​200

– USB cables: Wireworld Starlight; Vermöuth Audio Reference USB; ZenSati Zorro

– Speaker cables: WK Audio TheRay Speakers + SHUBI Custom Acoustic Stands MMS-1

– Power cables: Esprit Audio Alpha; Furutech FP-3TS762 / FI-28R / FI-E38R; Organic Audio Power + Furutech CF-080 Damping Ring; Acoustic Zen Gargantua II; Furutech Nanoflux Power NCF

– Power strip: Furutech e-TP60ER + Furutech FP-3TS762 / Fi-50 NCF(R) / FI-50M NCF(R)

– Wall socket: Furutech FT-SWS-D (R) NCF

– Switch: QSA Red + Silent Angel S28 pin + Farad Super6 power supply + Farad DC Level 2 copper cable

– Ethernet cable: In-akustik CAT6 Premium II; Audiomica Laboratory Anort Consequence, Artoc Ultra Reference, Arago Excellence; Furutech LAN-8 NCF; Next Level Tech NxLT LAN Flame

– Vibration damping board: Franc Audio Accessories Wood Block Slim Platform

– Speaker rack: Solid Tech Radius Duo 3

– Acoustic panel: Vicoustic Flat Panel VMT