Connected Fidelity AC-2K Reference

It at all times comes again to the mains. Perhaps one comfort of residing in these densely populated British Isles is {that a} majority of the inhabitants lives inside a couple of stones’ throw of a distribution sub‑station. And we have now a well-regulated provide that normally stays effectively inside tolerance of the mandated 230V AC +10/–6 % and 50 Hz ±1 %. But the quantity of RF noise using on the mains is simply going up as the trendy world depends on elevated use of radio and microwave communications, exterior and within the dwelling.

One strategy to counter such undesirable interference is to transform the standard mains feeding the system electronics right into a balanced mains provide, utilizing the identical precept as balanced sign interconnections through XLR socketry between units – creating section and anti-phase waveforms that may cancel out exterior intrusion by common-mode noise rejection.

Turning Live

In the case of mains energy, meaning turning Live and Neutral traces into ±120V AC, and utilizing a centre-tapped earth on a transformer as a brand new 0V floor connection. Balanced mains options are already utilized in hospitals and recording studios and the know-how is rising in popularity for dwelling audio methods. To energy an entire system does demand a decent-sized transformer with capability to spare, which normally means a big and large field weighing tens of kilos.

From new model Connected Fidelity we have now the AC-2K, a balanced mains transformer constructed right into a sturdy aluminium chassis with output voltage indicator on its entrance. Connected Fidelity is a sub-brand of distributor Air Audio, based by Michael Osborn and higher generally known as the founding father of Astin Trew, and latterly the importer of Hana moving-coil cartridges from Japan.

The AC-2K’s 2000VA-spec toroidal transformer ought to have the headroom to permit not simply low-power supply parts however amplifiers too up to some hundred watts of rated energy. In truth, and in defiance of many mains therapy options I’ve tried with energy amps, from the outset it was the amplifier that responded most positively to this new balanced provide.

The black anodised case with brushed pure entrance is giant however not big at 23cm vast and 18cm excessive, extending again 33cm, and at virtually 17kg it’s nonetheless comparatively man-liftable. The rear panel as customary has only one UK mains outlet and a 20A IEC energy inlet. Other choices can be found to order, together with two UK mains retailers, and EU or US retailers.

Power wire? Nein danke

There’s no energy wire supplied with AC-2K; Connected Fidelity is primarily a cable firm so upsell alternatives can be found. The take a look at unit was provided with a brand new cable simply added to the vary, the Chronos 2 (£840). It’s based mostly on a braided weave of cryogenically handled multistrand UP/OCC copper and silver-plated copper wires, totalling 12 sq. millimetre for every of the 2 energy traces, terminated with Furutech IEC and MS HD Power UK plugs.

Inside the field, safety circuitry on the balanced output aspect is specified as two residual present circuit breakers with overcurrent safety (RCBO). On the enter aspect is a soft-start relay swap to cut back switch-on surge. The toroidal transformer is mounted on a compliant anti-vibration assist plate, with transit screws to safe the mass when packed for delivery. And in a bid to extract the perfect efficiency from this transformer, it undergoes deep cryogenic therapy previous to set up in AC-2K, cycled by a industrial specialist all the way down to –195 °C in a course of that’s stated to learn the ferrous core of the transformer by growing the proportion of martensite and reducing austensite within the metal’s crystalline construction. And because the toroid is handled full with its copper wiring, there could also be optimistic results of chilly annealing on the first and secondary windings.

Cryogenic therapy can be marketed for the inner fuse and wiring in addition to the PCB and its parts, however not the Chtai mini circuit breakers or Songle soft-start relay, which might not safely survive a deep-freeze therapy.

In use the AC-2K remained blissfully silent, with no hint of background hum from its transformer. Nor did it journey the buyer unit on switch-on, which I’ve encountered with different balanced mains options. Inspired by professional items just like the Equitech Model Q, there’s a voltage output show, fortunately switchable and stored off for listening, with even the corporate admitting it has an influence on sound high quality. Referenced to different voltage meters it additionally appeared not significantly correct both, constantly studying over 4V too excessive. There is a bare-bones ‘Studio’ model of the AC‑2K (£1,995) with out the chocolate teapot read-out though this model additionally lacks the circuit breaker security options and decoupled transformer mounting.

Sound high quality

While checking out the facility provide to a system is important for good sound, there are many mains therapy merchandise that subtract as a lot from efficiency as they add. Excessive or the incorrect sort of mains filters, for instance, that add networks of resistors, capacitors and inductors within the curiosity of eradicating noise, might achieve this on the expense of ‘slowing’ down the sound, robbing dynamics or slam as they go. They might exist, however equally, in my expertise I’ve not discovered a shielded mains cable that has completed something apart from collapse the drama and dynamics from the music both.

This balanced mains provide is altogether completely different, and regardless of my greatest efforts to incorrect foot it, the important timing and dynamics remained intact – whereas the general sound was in respects displaying the sort of night-and-day variations that makes comparisons swift and decisive.

Limited by the solitary UK mains outlet, the AC-2K was first wired into the system with a six-way distribution board, a Nordost QB6 with V2 mains cable, which serves a Chord SPM 1200C energy amp and Rothwell Signature One phono stage. Playing vinyl from Clearaudio Innovation, the main transformation was the way in which that instrumental color was fleshed out, making a return to unbalanced mains seem as gray and flatter in timbre. Working by an previous favorite of the Peddlers’ Birthday album, the classical guitar that unusually supplies the principle accompaniment within the opening observe ‘Where Have All the Flowers Gone?’ appeared extra important, extra within the room and now fairly naturally positioned in its area. A shimmer of tambourine was unveiled brisker and cleaner, and together with Roy Philips’ vocals, was now clearly being fed by some traditional plate reverb for that 70s manufacturing. Image peak was shifted upwards, together with the sense of air as you discover as noise flooring are lowered. Playing the subsequent observe ‘Little Red Rooster’ with Philips behind his signature Hammond B3, the drawbars appeared to discover a new place, one I’d have to explain because the rippling-funky-gospel setting.

Given some solo piano recordings, modifications have been maybe not so manifest, and whereas Kempff’s enjoying of the Beethoven Pathétique didn’t so simply exhibit the modifications there was undeniably extra delicacy and nuance. A swap again to plain mains now confirmed a flatter depth perspective and a way that quick finger runs that punctuate the primary motion weren’t so fluently performed. And that’s one of many treasures of enhancing the standard of sound copy – as constancy is elevated, so too will be the standard of musicianship as appreciated by the listener.

The AC-2K was acquitting itself of the same old sins of mains therapy – the robbing of tempo, slewing of timing or subtraction of micro-details – however with my system at the very least there was a small matter of addition, and that was in bass richness. While it could preserve the tempo ticking alongside from prog rock to journey hop, I felt it may tickle up the mid-bass with a contact of euphony.

Played at appropriate live performance quantity, the Floyd stay CD efficiency of The Wall stored the architectural solidity from the rhythm part basis, with added focus to vocal components, and within the background acoustic of a extra convincingly cavernous Earls Court.

Happy hogging

This remaining outcome was solely after making an attempt numerous wiring mixtures of DAC and upsampler plugged into both the identical distribution board as the facility amp from AC-2K; on their very own direct from the wall; or with simply the digital supply parts on the balanced provide. As prompt in earlier trials, the Chord DAC/upsampler combo, with their pesky laptop computer SMPS provides, don’t make simple mains-sharing bedfellows with the amp and different analogue electronics, so have been as soon as once more relegated to their very own retailers with out the blessing of balanced mains. Or to place it one other approach: the Chord SPM 1200C energy amp was at its happiest when hogging the AC-2K alone.

Balanced mains from the AC-2K should depend as a kind of one-way dems, the place the sonic advantages make switching again to the previous regular an unwelcome journey. It presents cleaner, extra extremely resolving sound together with a mid-band declutter, with none elementary cramping of tempo and dynamics.

Technical specs

  • 2.0 kVA screened balanced transformer
  • 4 x rubber isolation mounts
  • UP/OCC inner wiring
  • Deep cryogenic therapy for transformer, fuse, wiring and PCB
  • Input socket 16 A IEC C20, gold-plated
  • Output socket UK 3-pin, gold-plated
  • Soft-start relay and resettable RCBO
  • Dimensions 230 × 185 × 330 mm (whd)
  • Weight 17.3 kg
  • Price £2,890


Connected Fidelity


UK Distributor

Air Audio


+44 (0)1491 629629

Back to Reviews

The put up Connected Fidelity AC-2K Reference appeared first on Hi-Fi+.

Select your currency