I didn’t know Okutsu Denko Co. before this review; I had no idea it even existed. As it turns out, it is quite well-known in Japan. The company specializes in power supply systems, and it entered the audio world in 2005 with the Air Cable brand. The pretext for that was the development of a new geometry of power cables, with air as the main insulator. The concept is not new – we may recall the American Tara Labs – but its realization by Okutsu Denko is innovative.
The cables consist of four tubes made of Teflon, centered around a copper wire in the middle acting as a “drain”, a protection wire. Two of these tubes house copper conductors. They are not straight but waved to minimize contact with the surrounding tubes, and so that they do not move. Shielding consists of three layers: copper tape, meshed carbon fiber and copper braid. The tubes are held in place by braided silk. The copper conductors purity has not been specified.
The company presently offers four models of power cables, two highest of which we received for testing. The top model, Extreme, has a smooth, transparent finish, reminding Acrolink, and a purple braid underneath. It is terminated with Oyaide 079 plugs, with their external screw-on part custom made of nicely finished titanium. The less expensive model, Prestige, with a blue mesh, has plugs with aluminum housing.

As there is no information about Air Cable available online in English, I asked the company for first hand information, especially for “High Fidelity”. Here’s the reply from the business owner:
Why Okutsu Denko (an electrical installation company) has become an audio cable manufacturer? It started in 2000 when power cables were recognized as an important sound improvement audio accessory. I had a chance to try several electrical cables (used for electrical installations) for my private recording studio, as my hobby, and I came across an interesting fact. I found a remarkable difference of the sound with different electrical cables (VVF and EM-EEF cables), and I discovered this difference is caused by shielding materials.
The structure of VVF and EM-EEF cables is basically same and the only difference is the shielding material (insulator) which is directly covering the conductor. A dielectric constant of the insulator has some influence to the sound quality. So, what is the insulation material with a lowest dielectric constant ? That is AIR. Unfortunately, there were no power cables with Air-Insulation only excepting a special heavy duty cable for high voltage equipments and a power line between pylon (naked conductor), therefore, I decided to produce an Air-shielding power cable of my own design.
In order to finalize the air cable, I installed “Digidesign ProTools HD” and did several tests together with professional recording engineers. First test samples were tested by some Japanese musicians and recording engineers, and very positive reputations from them made me decided to proceed with the production of the Air Cable.
As soon as the Air Cable obtained PSE (Japanese electrical safety standard), a patent was applied for the structure of Air Cable. Additionally, I also designed a special connecting method between a power plug and the air cable (patent pending), because a normal power plug is unable to tightly connect the air cable which is equipped with air tubes. Five years after starting a development of the air cable, this epoch-making air cable has finally been released into the market.

SOUND

Recordings used during auditions (selection):

• Blade Runner, soundtrack, muz. Vangelis, Universal, UICY-1401/3, Special Edition 3 x CD (1982/1991/2007).
• Paganini for two, Gil Shaham, Göran Söllscher, Deutsche Grammophon/JVC, 480 246-5, XRCD24 (1993/2009).
• Chet Baker, It could happen to you, Riverside/ZYX-Music, OJC20 303-2, 20-bit Super Bit Mapping CD (1958/1987).
• Chopin, 4 Scherzi, Ivo Pogorelich, Deutsche Grammophon, 439 947-2, CD (1998).
• Diorama, The art of creating confusing Spirits, Accession Records, EFA 23450-2, CD (2004).
• e.s.t. Esbjörn Svenson Trio, 301, ACT Music + Vision, ACT 9029-2, CD (2012).
• Ella Fitzgerald & Louis Armstrong, Ella and Louis, Verve/Lasting Impression Music, LIM UHD 045, UltraHD CD (2010).
• Glen Gould, Bach: The Art Of The Fugue, Sony Music/Sony Classical, SMK 52 595, The Glen Gould Edition, SBM CD (1997).
• Handel, Arias for Cuzzoni, Simone Kermes, Lautten Compagney Berlin, dyr. Wolfgang Katschner, Berlin Classic, 0016422BC, CD (2009).
• Jean Michel Jarre, Magnetic Fields, Epic/Sony Music, 488138 2, CD (1981/1997).
• Lisa Gerrard, The Silver Tree, 4AD/Sonic Records, SON212, CD (2006).
• Manaam, Się ściemnia…, Kamiling Co./Pomaton, 957952, CD (1991/2011).
• Nosowska, 8, Supersam Music, SM 01, CD (2011).
• Novika, Tricks of life, Kayax 013, CD (2006).
• Paul McCartney, Kisses On The Bottom, Universal International [Japan], UCCO-3038, SHM-CD (2012).
• Sara K., Don’t I Know You From Somewhere?, Stockfisch, SFR 357.6055.2, CD. · The Modern Jazz Quartet, The Sheriff, Atlantic/Warner Music Japan, WPCR-25129, CD (1964/2006).

Japanese editions available from .

AIR-PC (Prestige Custom)
The audition of this cable was a pleasant experience, although I must say that the nature of the introduced sonic changes did not quite suit my preferences and did not provide the best match for my system.
In this cable the emphasis was clearly shifted from the lower midrange, as in the reference Acrolink, to the treble. It’s not even the higher midrange but the high end. This results in a very detailed sound, bringing loads of information about cymbals, extra-musical events, the master tape noise, etc. For example, I could perfectly hear the difference in the type of noise between Chet Baker’s and The Modern Jazz Quartet recordings – Chet sounded more “old-school,” had a narrower bandwidth. And although we listen to the music, not the noise, such broad-frequency noise as that of the master tape is a great indicator of what happens with the sound in general.

The Japanese cables, at least those that I know, are characteristic in that the more powerful treble does not mean brightening up or harshness. This is a phenomenon, for which I cannot find explanation, but I know it from auditioning and it is repeatable. It’s as if someone lit a stronger light in the room without flashy accentuation of bright surfaces, but rather emphasizing contours, depth, etc. I think it has something to do with low “background” noise, something that blurs the small signals. The AIR-PC Air Cable sounds exactly the same – a deep calm in the background, emphasis on the foreground information at the expense of the scene depth, but with simultaneous vividness of the instruments. These are not as clearly shaped as with Acrolink, since they are formed differently. Their attack is shown more strongly; there is more micro-information around them.
The sound is not very resolved or particularly selective. This does not mean that it is unsatisfactory, but given its high cost, the cable is just average in this respect – maybe slightly better than the Oyaide Tunami GPX-R, but not as good as the Harmonix X-DC350M2R Improved-Version. It’s just that – and it is another special feature of the Japanese cables – it still mops the floor with most cables I know, from companies outside the Land of the Rising Sun.
It’s a cable that changes the signal in such a way as to bring up the first plan, to show a lot of information (details), yet without annoying coloration and without brightening. It will prove to be a perfect match for systems that need a bit more life, better contouring, but without brightening up the sound, without adding annoying elements.
For it is a very smooth and consistent sound. It is a pleasure to listen to, even if – as in my case – the listener’s preferences are slightly different. It simply cannot be underestimated.

AIR-EX (Extreme)
The other reviewed Japanese cable is more sophisticated. This does not mean that the AIR-PC was poor or lacking – it is a really solid contender, with clean treble and good detailness. Only that the AIR-EX additionally brings depth.
At the same time, the fabulously clean treble remains. When I fired up with this cable the new re-release of the album Się ściemnia… by Maanam, one of my favorite albums of this band, the opening cymbal crashes and noise makers literally exploded from my Harbeths’ tweeters. They were neither sharp nor bright, but simply clean. I have not long heard such detailed cymbal attack, so precisely accented decay – even my Acrolinks sound slightly duller in this respect, not by much, but still. For that matter, Acrolinks generally sound darker, just as the mentioned Harmonix. Compared with the Air Cable, the latter is simply warm.
This is probably the main strength of this cable, which will allow it to fit well in even the most expensive systems. No matter what we play with it, be it Maanam kind of music, or Sarah K., or maybe the new Paul McCartney’s album Kisses of The Bottom, we always get a fresh, ranging, open sound. I can almost see a smile of satisfaction on the faces of tube amplifiers owners, for whom the AIR-EX cable will be like a breath of fresh, crisp air. Where there has only been warmth and honey, there will pop up a bit of zing, a light draft will come.
The cable presents the sound in a very dynamic way. This is not a sleepy tone, but rather a sort of sonic “booster”.
What helps it is color shaping. It has slightly accented extremes of the sonic range, which results in a slight attenuation in the area of a few hundred Hz, somewhere around 200-300 Hz. There is no merging of sounds; the attack is very nicely emphasized and this type of sound proves great in a quiet listening, as if addressing the limitations of human auditory system, where sensitivity at the frequency spectrum extremes drops with the sound volume decrease.
However, these modifications are not too significant, or perhaps too offensive, to speak directly of overemphasized treble or bass. As with the previous cable, it is a matter of accent shift. Quantitatively, these changes are therefore not as significant as for example changing columns or components, but ultimately it is they – the way I hear it – that give the audio system polish and final shape.

Conclusion
Both Air Cable cables from Okutsu Denko Co. have quite similarly structured sonics – very clean treble, strong attack and much air. They are without any doubt a great match for tube systems, usually lacking in these areas. Of the two, the AIR-EX cable is much better. The AIR-PC is pretty good, but I would not hesitate to pick the more expensive model, even if I had to wait and save more money. It is worth doing, because the cable is exceptional, with incredibly clean treble.

Review methodology The review was an A-B comparison with A and B known. The Air Cable cables were compared to the reference cable, the Acrolink Mexcel 7N-PC9300, as well as the Harmonix X-DC350M2R Improved-Version (review HERE). Music samples were 2 minutes long. The cables powered the following devices: Ancient Audio Lektor AIR V-edition CD player and Leben CS-1000P amplifier.