From the top. Our 4-driver 3-way Swiss speakers blend a custom small AlNiCo widebander with an upfiring Raal ribbon at an unconventionally high ~10kHz, so far beyond our hearing's range of greatest sensitivity. The biggest change which switching between DACs made here was the 3kHz+ band's energy. With the D10 it had more. That gave vocals greater presence, immediacy and forward projection. The Terminator played it a bit more laid-back and relaxed. Interestingly, this didn't present as an upshift in tonal balance. The D10 covered the low-end as anchored and weighty as the Denafrips. Still, my perception of air and brilliance was higher with the COS, so also its degree of recorded venue intelligibility when very faint reflections paint the picture like flashes of lightning do to a nocturnal landscape.

Soundaware D100Pro SD transport ⇒ coax out Terminator, AES/EBU out D10 ⇒ both into icOn via identical Crystal Cable XLR ⇒ Bakoon AMP-13R ⇒ sound|kaos Vox 3awf ⇒ Zu Submission 

I considered its effect on the sense of musical flow versus propulsion—ease versus pressure, looseness versus tautness—negligible. On that and the other scores which dissecting a musical performance nets during audiophile discussions, I thought the two converters surprisingly similar so in the same class. The Taiwanese challenger simply packed far more utility. Rather than Jack of all trades but master of none, going neck to neck with the Terminator made the D10 equally serious on all its fronts. And that's the takeaway of this review. Very close to the D1 as DAC/pre, superior to the H1 as headphone amp, the D10 isn't just loaded for bear on paper. And that's before testing its streamer and phono boards which will be for another writer to do.

The only other nit past absentee black-out option during play was full black-out during standby. I happen to think that there ought to be a small visual indicator to distinguish between full/half off. Presently there isn't. Looking at the D10 in a rack, one can't tell whether it's in standby or off, period. But that's neither here nor there. The only real problem concerns the D1. While the D10 was longer coming that first scheduled, hearing it confirms that its designers spent the extra time not just perfecting their complicated enclosure. Sonically it's unreasonably accomplished for selling at half whilst doubling usage plus bolting on two more optional features each for a surcharge. COS' wood-shack period clearly chipped away at extra performance points so effectively that their prior flagship got knee-capped in the process. Now that's progress. For all the obvious reasons, it's also not something most companies would dare to do without billing extra.

Of the 3-in-1 aspects I could cover, my personal favorite was the sum total of headfi amp + DAC. I love headphones. Fronted correctly and accounting for the fundamental differences to SpeakerFi, headfi with modern flagships eclipses all but the room-luckiest of big systems on resolution, linearity and bandwidth. Now replace "fronted correctly" with the D10. That equation fulfills all the way up to the notoriously inefficient HifiMan Susvara but includes super sensitivos like Final's Sonorous X. Then pull out the headphones to fire up your speaker amp/s instead. The same very high standards transfer to your big system – if your room cooperates reasonably enough. Our small mains crossed at 40Hz to a big sub match their 6x4m space ideally so the room cooperates with just regular furnishings as 'treatment'.

So… cos célèbre? Absolutely and without apologies. The COS Engineering D10 from Taiwan is a modern multi talent whose modular concept allows each buyer to bundle the features they want. With the slide-in modules, this can easily be post purchase, no dealer visit or two-way shipping involved. It's been strange times but 2020 hindsight calls the D10 one highlight of this year!