Srajan Ebaen
Financial interests: click here
Sources: 27" iMac with 5K Retina display, 4GHz quad-core engine with 4.4GHz turbo boost, 3TB Fusion Drive, 16GB SDRAM, OSX Yosemite, PureMusic 3.01, Tidal & Qobuz lossless streaming, COS Engineering D1 & H1, AURALiC Vega, Aqua Hifi Formula, Fore Audio DAISy 1, Apple iPod Classic 160GB (AIFF), Astell& Kern AK100 modified by Red Wine Audio, Cambridge Audio iD100, Pro-Ject Dock Box S Digital, Pure i20, Questyle QP1R
Preamplifier: Nagra Jazz, Vinnie Rossi LIO (AVC module), COS Engineering D1, Wyred4Sound STP-SE Stage II
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1, F5, F6, F7; Crayon Audio CFA-1.2; Goldmund Job 225; Aura Note Premier; Wyred4Sound mINT; Nord Acoustics One SE Up NC500MB monos; LinnenberG Allego monos
Loudspeakers: Audio Physic Codex; EnigmAcoustics Mythology 1; Boenicke Audio W5se; Zu Audio Druid V & Submission; German Physiks HRS-120; Eversound Essence
Cables: Complete loom of Zu Event; Ocellia OCC loom: KingRex uArt, Zu and LightHarmonic LightSpeed double-header USB cables; Tombo Trøn S/PDIF; van den Hul AES/EBU; AudioQuest Diamond glass-fibre Toslink; Black Cat Cable redlevel Lupo
Power delivery: Vibex Granada/Alhambra and Three 11R, Titan Audio Eros cords between wall and conditioners and on the amp/s
Equipment rack: Artesania Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands [on loan]
Sundry accessories: Acoustic System resonators
Room: Rectangular 5.5 x 15m open floor plan with two-storey gabled ceiling, wood-sleeved steel trusses and stone-over-concrete flooring
Review component retail: €3'200 without volume control (D2), €3'900 with volume and remote control (D2V)

Emoji queen Maggie Chern's email images set the mood. COS Engineering's cookout was about to serve up a new dish. Regular readers know that I reviewed then bought their D1 DAC/preamp and subsequently wrote up then acquired the H1 fully balanced headfi converter. I like to put my wallet where my pen pressed hardest. Here it makes me a fully invested COS champion. My inner betting man was certain. Act III in this opera from Taiwan would be a class A/B mono amp inside the small chassis of the H1 whose RCA outputs double as minimalist preamp without remote. Add amp. Presto, a full COS mini system. But, Maggie's emoji blew kisses not at that but their new D2 DAC. It's available with/without volume. This bet I'd have lost. It's why my gambling man stays in where he can't do damage. Dommage as the French would say. Too bad. Not! After two Blue Moon awards, anything COS gets me excited. I'd simply not expected another DAC.

Playing email ping pong with Maggie, I learnt why. An amp was on the drawing board but the quicker project to final was the D2. It's seriously less coin than the D1 and shaves off cosmetic extravagance. As COS learnt after their D1 left Kaohsiung Port under a €9'000 banner, for a young hifi company it's not easy to grow a business with a costly first and only product. That's why they worked hard to bring in the H1 at €2'500 ex VAT. With the D1 having set a high bar for designer styling, COS went through a few suppliers before the simpler H1 case passed inspection. Once it went into production, their engineers looked at how to repackage the D1 innards into the smaller extrusion, then shrink, substitute or omit whatever wouldn't fit its size or target bill. With the H1 already containing a D/A converter scaled down from the D1, the D2's removal of the H1's headfi amp could load up again on the digital side; perhaps even the power supply?

It's a clever way to spread out mature tech over multiple models. Each gets a clearly defined user profile. Like the D1/H1 do, the D2's now optional volume operates in the analog domain. There's no bit stripping or resolution loss at low levels. If you're still hazy on COS the name, it's short for connoisseurs of sound. And they're not just saying that. When I told Maggie of my assumption that when they first drew up the D1, they had no notion of high-end's deeply layered margins, "you're totally right. We had no idea. If we knew, the D1 might have been born with a different look". It's reminiscent of Mola-Mola's Kaluga amplifier. Its wave-shaped chassis went through three machine shops before it passed muster. That not only delayed first production. It also weighed down the retail price. Anyone missing in the D2/H1 the D1's push/turn knob set into a massive baffle and the LED half circle below must acknowledge their disproportionate impact on the sticker. If those styling cues are important, the D1 remains the one and only. Pay up!

The COSway to the D2. To recap company history, COS was founded by friends Stephen (Gong Xixun), Oliver (Wang Fuquan) and CC (Fang Zhiquiang) who had previously worked at the same medical electronics firm and shared a love of hifi and good sound. The D1 was preceded by 3 years of internal R&D which included writing their own filter algorithm. Much critical listening used Stephen's office system of Sonus faber Amati speakers, Goldmund Telos 600 monos and Nottingham Spacedeck turntable*. The H1 took two years to perfect. This included three different machine shops until they signed off on the casing. Whilst they would likely prefer to move faster, their standards refuse visible screw heads, bent sheet metal and even minor anodizing imperfections. This imposes limitations on how quickly any breadboarded circuit accompanied by detailed 3D drawings will manifest in final production. As all women know, beauty costs. As all business knows, time is money, too. As small hifi firms know or learn soon enough, to compete with Apple on finish and industrial design without Cupertino's vast engineering department, resources and FoxConn manufacture is no walk in the park.
* Other gear owned amongst the principals includes, for sources, a Blu/DAC64 duo from Chord and a N°30.5/31.5 combo from Mark Levinson; for preamps, a C42 and C500c from McIntosh, a N°32 from Mark Levinson and a tubed Cabernet from Supratek; for amps three MC352 from McIntosh, a DM-10 from Densen and a 2060 from Boulder; and for speakers two pairs of Stradivari and one Cremona from Sonus faber, a Kingdom 12 from Tannoy and a 6 from Dynaudio. For cables, they all favour Van DenHul. This collection of brands and models gives a good indication on their sonic preferences.

"The D2 should hopefully be out by April. Our retailers reported how some of their clients use our H1 without headphones just as a DAC/preamp. For them, the D2 becomes the perfect go-to model if a D1 remains out of reach." By October 27th, Stephen checked in. "After months of further tweaking and thorough auditions, CC—our resident sound master—finally approved the D2. As the D1's little brother, I probably shouldn't say how much it excels but for sure it performs very close. In the last moment we also decided to make for it a metal remote that will be more affordable than the D1's. This will take a few more weeks."

The symbol left of 'USB 2.0' denotes buffer engaged. Signal lock shows with a musical note to the right of the displayed input.

CC's status as sonic sifu isn't capricious. Unlike Stephen, Oliver and Maggie who sweat production and marketing schedules, CC gets to exercise veto powers based purely on performance. That's his function. During a Munich HighEnd 2017 show meeting, Stephen confessed how CC gets to be most unreasonable and often forces their team into more tweaking and experiments which may (or not) move performance up and forward by an inch. In this case, the D1 was CC's stubborn reference. That at well more than twice the price it shouldn't just be bigger, heavier and blingier to him wasn't logical. As a result, he cost production an extra half year to final this fully balanced circuit with integer upsampling to 176.4 or 192kHz at 32-bit precision via a custom linear-phase FIR filter. In the V-for-volume version, a 0.1% tolerance switched resistor ladder attenuates the signal. A 1-second buffer—defeatable by rear toggle for video lip sync—reclocks the signal for <1ps jitter and there's galvanic isolation between digital and analog circuits.

Another rear toggle selects between USB 1.0/2.0. The former is a Windows saver if one doesn't want to install a driver. The latter supports up to 384kHz. A universal 100-240VAC switch-mode power supply makes for one global model. Full-scale output is 2/4Vrms on RCA/XLR respectively, S/N ratio >110dB A-weighted. The white Oled display resolves 128x64 pixels and overall case dimensions are 26 x 25 x 6cm WxHxD with a weight of 3.5kg. Standby draw is half a watt and usual operation occurs below 15.

When the review loaner shipped by the end of November, it was anounced by this email: "We dispatched to you a D2V plus buffer board for DAC-only use this morning. Please refer to the attached documents. The metal not plastic remote will take more time. We made prototypes but beauty comes at a price. So we just have to work harder and hopefully can make something beautiful that's still affordable." The remote is obviously exclusive to the D2V version. Conversion from without-to-with volume is child's play. It involves merely removal of the front panel by first removing the front footers to gain access to the fixing bolts beneath; disconnecting the display ribbon cable; loosening the back panel; finally pulling out the motherboard from its side extrusion rails. Pop out the buffer board by its pin headers, replace with volume control board. Reverse previous process. Presto. 10 careful minutes ought to do it, no return to Taiwan necessary.

About those RJ45 COSlink ports, "they are indeed for 2-way comm protocol but purely digital hence no replacements for the standard analog RCA/XLR sockets. They are currently intended for our pending power amplifier whose feature set hasn't been fixed yet." So perhaps these would just be on/off triggers; perhaps more. Time would tell. Already, the twosome scheme did predict mono amps.