Round 1. Leisurely switching inputs by remote whilst both feeds ran through their 15 tracks clarified right off that they were equal but not absolutely identical. The domain in which this small difference occurred was contrast. The textural offset was transient vs. decay. The flavour was sharp vs. soft. The USB stream had slightly higher contrast. The effect was very similar to playing something louder by so little that it doesn't yet register as really louder but as stronger contrast. Anyone who has ever manipulated the contrast setting on a television understands how the effect is achieved. Rafael Cortés playing flamenco guitar on Cagiñi was spicier and more leading-edge tweaked off the iMac. Hence it was sharper, with a tad more on-string metal action. A saucy Middle Eastern string orchestra backing male and female solo vocals on Magida el Roumi's Ghazal felt softer and more decay-polished with the La Diva. With such more 'reverberant' fare, the same action suggested a bit more body or fullness. Sabine Meyer's Bläserensemble with Antonin Dvorak's Serenade in D Minor Op. 44 thus got the nod on the Italian disc spinner whilst Omar Bashir's vigorous oud favoured the iMac. Sœur Marie Keyrouz's Byzantine vocal exploits in church acoustics and against the backing forces of the Ensemble de la Paix went to Milan, Aytac Dogan's plucked qanun to Cupertino. That match was a draw.

It's important to state that the magnitude of this difference was so mild that your ear/brain would account for it in minutes if not seconds. In short, any to-buy-or-not decision would likely be based purely on what you already owned to call it quits right there. Mind you, this statement doesn't yet factor high-resolution files, DSD or the sheer convenience of having at your finger tips a vast library (your own or cloud-based) and being able to cross-link tracks without swapping CDs and cueing up tracks. This exercise deliberately disregards creature comforts. It concerns itself solely with sonics. On that count and with my COS Engineering DAC which wasn't yet capable of exploiting the perhaps superior AES/EBU or I²S connection, my internal judge felt reassured that iMac-based PureMusic-optimized transporting competed fair and square with a twice-priced dedicated CD transport. Any concerns to the contrary were off the hook. Of course the inverse would be just a true. Someone already owning the La Diva and being purely focused on sound wouldn't see any compelling reason to switch allegiances whilst using the COS DAC.

Round 2. To play with its stablemate La Scala Mk.II DAC, I reconfigured the system to include the AbysSound ASP-1000 fully balanced transistor preamp to control volume. The first order of business was comparing S/PDIF, AES/EBU and I²S. In a nod at sacred cows and Barbarian axes, the technically arguably best format ran with perfectly blasé frumpy Ethernet patch cord. The other sockets pressed their case with more audiophile variants from Tombo and van den Hul.

Even though its cable was costliest by far, S/PDIF via BNC exhibited the most edge. It was the adolescent agitator of the bunch. AES/EBU played it calmer, mellower and fuller. Taking the cake however was the parallel format. With it the sound settled down fully and blossomed. This was particularly amusing considering its €0.80/m CAT5 link. If you've played endless switcheroo between various digital filters and found the differences between them minuscule at best, this comparison played it bigger and more obvious. And, the gap between S/PDIF and AES/EBU was narrower than between AES/EBU and I²S. Not since my long-departed Zanden Audio separates had I played with I²S. Clearly this rare non-standardized transmission protocol—some implement it on HDMI, some on S-video, some on RJ45—still had legs.

With a very clear best pathway established, it was time to toss the losers and pit USB against I²S. Given this preamble, my inner judge was admittedly no longer feeling haughty. Fidgety and jittery were his words du jour. Hey, rattling that old geezer to the core was a good thing. Live and learn remains the motto.