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Like its big brother, the Concero's casing is carved out meticulously. This even includes milled and threaded stand-offs for the motherboard and deeper pockets for the Chinese PE65812NL pulse transformer and vertical LED board that must show red for power/no lock, blue for lock without upsampling and magenta for lock with IIR/apodizing filter/integer upsampling. Eight screws put it all together; four for the board, four hidden beneath tiny rubber bumpers to seal the bottom lid. Assembly of the Concero at Resonessence thus takes about a minute since actual board population and case work are outsourced to local subcontractors.

As the 9023 Sabre on-chip recipe predicted, there's really not much to the board proper. The main brain to control the various firmware functions is a Resonessence-programmed Spartan-6 Xilinx gate array.

There are discrete clocks for the audio and video-related 44.1/48kHz sampling frequencies, a few other bits and bobs plus board-mounted connectors and that's it. Also in the small shipping box were a 15-page owner's manual, a generic USB cable and Apple's remote and USB wall adaptor with US plug.

My first order of business was confirming iPod happiness. As I'd learnt with Burson's Sabre-powered Conductor, that's not a given when a maker fails to account for sufficient data-rate speed-margin error to accommodate the lower-tolerance output of such sources. Burson's Conductor stutters when fed a digital iPod signal. It suffers data dropouts and repeat relocks accompanied by clicking noises. The Concero thus got leashed to my customary Cambridge Audio iD100 dock's S/PDIF output via Chris Sommovigo's very best cable in lieu of the usual Zodiac Gold, from there into Bakoon's amazing AMP-11R which powers Beyerdynamic's sealed T5p or the open-backed Audez'e LCD-2.

To a far lesser extent than with the Conductor and sans accompanying relay clicks, I once again suffered the occasional drop-out and to an even lesser extent also in USB bridge mode* when I came off my usual quad-core iMac. My contact Mark Mallinson at Resonessence talked to their lead engineer and confirmed that this sensitivity issue of the S/PDIF receiver should be easily fixable with a firmware tweak via direct download. In the meantime I set the iPod to shuffle and endless repeat to hasten the Concero's break-in.

* USB bridge mode hiccups turned out to be due to an apparent minor incompatibility between Mountain Lion (I'd recently updated my OS from Lion) and the very latest Audirvana Reverting back to PureMusic 1.86 became perfectly smooth sailing as usual. The minor dropouts thus were exclusive to the iPod/Cambridge source.

In apodizing 176.4kHz mode feeding APL Hifi NWO-M in DAC mode, Audiophilleo 2 for scale

Grabbing one of my Apple remotes confirmed control over display dim. Sustained press of 'down' dims, 'up' gets brighter over a surprisingly broad range. For filter mode pressing 'menu' once engages the IIR filter/upsampling; pressing 'menu' again gets you to the apodizing filter with upsampling and pressing 'menu' a 3rd time returns to native mode. Hijacking an existing remote and its code was a stroke of genius particularly with as slick a mini wand as Apple's. If your music player of choice is set to upsampling—I favor Audirvana in direct/integer mode and 4 x upsampling to 176.4kHz—the Concero's filters won't kick in. This black box only upsamples 44.1/48kHz data. If hitting 'menu' repeatedly won't net magenta, that's why. Due to its socket orientation, USB bridge mode with the Concero does require an S/PDIF cable. My Audiophilleo 2 cleverly gets away with just a short hardware adaptor that mounts directly between its BNC output and the receiving machine's coax or BNC input. Of course the Concero is bigger and heavier to begin with. This would probably advise against hanging it off the back of a DAC in the first place.