Air Audio Services AC-2K Balanced Mains Transformer

Air Audio is a small and unassuming manufacturing and distribution outfit located not far from the City of Oxford in the UK, and run by long-time high-end audio guru Michael Osborn. While specializing in the sell-through of extreme-performance cartridges and cables, the team also turn their hand to the design and fabrication of audio accessories and components. Seasoned two-channel audiophiles might be familiar with Osborn’s name as chief engineer of the Astin Trew audio separates brand, the company he founded in 2003.

While it is not uncommon for home theater afficionados to question the efficacy of noise-reducing and power stabilizing gizmos, Air Audio nevertheless asked if we would like to review its latest balanced mains transformer, the AC-2K. The company is particularly keen to dip its toe into the home theater arena, not least because it has recently developed a rack-mount version of the unit, which had previously only been available as a standalone block. Both SKUs are now available direct from the company in both 120v (US) and 220-240v (Europe) versions. As opposed to regular power supplies, Air Audio insists that the AC-2K’s lowering of the audio noise floor results in vastly improved soundstage depth and detail perception, as well as enhanced video performance.

AC-2K Rack Mount Version

Design and features

Weighing in at 37lbs (17Kg), the first thing a new user will notice about either the standalone or rack-mount AC-2K after removing the sturdy packaging is that this is not a machine you will want to move from one location to another on a regular basis. In the case of the 3U-height rack version, it should simply be a case of screw mounting, plugging into the wall outlet, attaching power cords of up to six components (Blu-ray players, receivers, power amps etc.), and then forgetting. Furthermore, unlike the kind of toys that home theater enthusiasts are used to playing with, there are obviously no remote controls or endless on-screen menus to navigate. There are merely one front-placed power on/off switch and a rear-mounted toggle for the red LED output voltage display on the front panel, should you choose to defeat its illumination.

AC-2K Standalone Version

Air Audio goes to some lengths to emphasize that balanced mains transformers are used extensively in recording, radio and TV transmission studios and environments to lower the noise floor. Among the key benefits of these residential units are the removal of RF pick up from power cords, elimination of AC/DC ‘noise’, reduced interference between audio and AV components and optimized power delivery. Using balanced mains has a further advantage, according to Michael Osborn, in that cables used to carry the power from the AC-2K are “less critical.” That is not to say that better cables will not improve sound quality, but the RF and other noise usually picked up from unshielded mains cables is cancelled out “…so more expensive shielded mains cables become unnecessary.”

The AC-2K is supplied by a massive specially built low impedance 2KVA balanced output transformer whose core is “impregnated with varnish”, the center of which is filled in with resin to reduce mechanical buzz. The transformers are ‘treated’ cryogenically which increases their power delivery, we are told. As if that were not going far enough, it is also mechanically isolated on an anti-vibration platform within the rack mount version. Good quality input and output sockets are mounted on the rear face, supplied by high purity copper internal wiring. As well as the integral ‘soft-start’ and anti-surge protection, there is an optional DC blocker circuit available if required. The standalone ‘audiophile’ version uses a double gold-plated output socket, a gold-plated C19 (16A) IEC input socket, plus additional sound and vibration damping elements.

In Use and Performance

Probably like others in the home theater community, I tend to raise a somewhat cynical eyebrow when confronted with esoteric magic boxes from the world of two-channel audio. After plugging all my pre- and power amps, disc player and projector into the rack-mount AC-2K, I fired up my system, and proceeded to place the UHD Blu-ray of Return of the Jedi into the spinner. I had already decided that I would run my non-scientific A/B comparisons by rather unceremoniously unplugging the unit and restoring all my component power cords to their usual surge-protected strips. I would also listen at identical volume levels for all content. This would allow me to detect any shortcomings in my system, if they existed, after removing the AC-2K from the circuit.

AC-2K Standalone Version (Rear View)

The opening sequence of ROTJ where Tie Fighters power off to the left the soundstage was both huge in scale and almost “holographic” (as Air Audio suggests in its literature that performance might be). When I immediately reverted to connecting my power strips to the wall outlet, the same excerpt dropped in energy, and its dimension was partially curtailed. Furthermore, the timpani in the opening Williams theme had lost some of their acute definition and resonance.

While those qualities had certainly impressed me, it wasn’t until I listened to some two channel sources that I understood the full potential of the AC-2K. On Talvin Singh’s 2001 CD Ha, the opening track “One” propelled the electronic bass drum thuds to a new level of precision and power, fusing midrange and bass with spot-on timing and a marked punch. It was also a delight to hear the strings on my Naxos recording of Stravinsky’s Pulcinella suddenly find their natural, clean and bright state. I have my reservations about that particular recording with strings often sounding a little dirty and gristly, but the improvements here were enlightening.

Because my 4K video face-offs were hampered by long projector cool-down cycles, I was unable to conclusively deduce that the AC-2K lifted video quality. But I was anecdotally aware of finer contrast and more stable grain structure, particularly on 4K Blu-rays transferred from 35mm film elements.

Conclusion

With comparatively low expectations for the performance enhancements that the AC-2K claimed to offer, I was indeed surprised – and actually quite stunned – by what a boost in fidelity and resolution the unit could achieve. Of all the components I have had the pleasure of cycling through my system in the past few years, this is one I was extremely reluctant to have to return to the manufacturer. While various forms of snake oil are peddled to audio- and cinephiles with alarming regularity, it’s refreshing to see that a box as understated as the AC-2K can genuinely lift your entire system to another level.

Notes on Purchasing, Shipping and Returns from the Manufacturer

The 19″ rack-mounted AC-2K with 120VAC input to 60/60VAC balanced output to six sockets is priced at c.$1,750 (GBP £1,299). It incorporates a standard fused C14 IEC mains power input socket, with on/off mains input switch on the front face, along with a switchable output voltage display.

The US plug to C14 IEC mains cable at 24″ long, using gold plated audiophile plugs and the OCC-UP silver/gold plated copper mains cable is c.$335 (GBP £249.00) plus shipping if bought with the AC-2K. This ‘audiophile’ quality cable is offered at trade price with a further charge of c.$31 (GBP £23) per each additional foot of cable, if required. However, any locally bought power cable using 16AWG or above will suffice.

Import duty is 1.6%, paid at the US end plus small admin fee. A 3-5 day air freight service through FedEx can be arranged at around GBP £110.00 including all packaging and insurance for the above. Lead time is usually 3 – 4 weeks and return policy is 30 days. Please email [email protected] to place an order or if you have questions about the company’s products. Company website is www.airaudio.co.uk.