Reviewer: Srajan Ebaen
Financial interests: click here
Sources: 2TB iMac 27" quad-core w. 16GB RAM running OWS 10.8.2, PureMusic 2.02, Audirvana 1.5.10, Metrum Hex, AURALiC Vega, Aqua Hifi La Scala MkII, SOtM dX-USB HD w. super-clock upgrade & mBPS-d2s, Apple iPod Classic 160GB (AIFF), Astell& Kern AK100 modified by Red Wine Audio, Cambridge Audio iD100, Pro-Ject Dock Box S Digital, Pure i20
Preamplifier: Nagra Jazz, Esoteric C-03, Bent Audio Tap-X
Power & integrated amplifiers: Pass Labs XA30.8; FirstWatt SIT1, F6; Crayon Audio CFA-1.2; Goldmund Job 225; Gato Audio DIA-250; Aura Note Premier; Wyred4Sound mINT; AURALiC Merak [on loan]
Loudspeakers: Albedo Audio Aptica; soundkaos Wave 40; Boenicke Audio W5se; Zu Audio Submission; German Physiks HRS-120, Gallo Strada II w. TR-3D subwoofer; Zugspitz Klang Seligkeit [on review]
Cables: Complete loom of Zu Event; KingRex uArt, Zu and LightHarmonic LightSpeed double-header USB cables; Tombo Trøn S/PDIF; van den Hul AES/EBU; AudioQuest Diamond glass-fibre Toslink; Arkana Research XLR/RCA and speaker cables [on loan], Sablon Audio Petit Corona power cords [on loan]
Power delivery: Vibex Granada/Alhambra on all components, GigaWatt PF-2 on amps
Equipment rack: Artesania Audio Exoteryc double-wide 3-tier with optional glass shelves, Rajasthani hardwood rack for amps
Sundry accessories: Acoustic System resonators
Room: Irregularly shaped 9.5 x 10m open floor plan with additional 2nd-floor loft; wood-paneled sloping ceiling; parquet flooring; lots of non-parallel surfaces (pictorial tour here)
Review component retail in the US: $9'000

After introducing herself
with a thumb nail photo of the product—the COS Engineering website just then was still under development—Maggie Chern announced that they would like to submit their maiden effort to Stephæn for review. After looking over the attached prospectus, our man in the US courteously declined. He cited his predilection for NOS DACs and concomitant bias against all up/oversampling shenanigans as making him the wrong man for the job. Asking Maggie who their #2 choice might be, my name came up. "We are a new start-up company with limited funds for sales/marketing, hence we first aim for the US (we only speak English in addition to Chinese)." Not only was her English flawless, the proposed DAC/preamp called D1 was one natty dresser. Minimalist in the best Scandinavian design tradition, with only a flush-mounted but top-protruding volume wheel and pin-prick LED circle plus IR eye and engraved logo on the front, close inspection of the rear panel revealed a 'made in Taiwan' declaration of origin. This explained Maggie's European first name and Asian family name. All Pacific rim folks of my acquaintance favour such a combination: Ronald Kwok, Sam Ngyuen, Simon Lee.

The product PDF sketched out the company: "COS Engineering was founded by three close friends who are serious about audio entertainment. With an aversion to cacophony, an aspiration for style and a penchant for simplicity, the founders have harnessed extensive knowledge and experience in mathematics, electronics and communication to research and design. The objective is to offer gear featuring musicality as well as aesthetics." With one out of two cited goals aced almost instantly, my curiosity about the musicality bit was piqued. I'd of course already looked over the feature list to have proper traction.

To wit, minimalist but bona fide analogue preamp functionality. That's accomplished by way of single RCA/XLR input pairs—the D1 is fully balanced—and analog-domain resistor/relay volume in 256 x 0.25dB steps over a 64dB range with better than ±0.1dB accuracy. In my book, the latter is the only credible way to sell an amplifier-direct connection for any DAC with high-end pretensions. Digital attenuation works well over a restricted range. Eventually it turns lossy though. That means tonal bleaching, weight loss and dimensional flattening. An uncompromised preamp must remain compelling even at whisper levels. Quoting off its spec sheet, the D1's analog inputs, without overloading, can process up to 8/16V on RCA/XLR respectively whilst showing their sources a 100KΩ input impedance. Z-out is 100/200Ω on RCA/XLR. Max voltage swing is 8/16V, S/N ratio >110dB unweighted. Finally, the digital filter is proprietary to the company. It's a FIR-bared linear phase affair handled by a 3'648 millions multiply and add per second DSP. Mechanical specs are dimensions of 415x280x100mm WxDxH. Weight is 8.6kg. An external voltage selector enables the same unit to work on 100-120 and 200-240VAC wall power. Draw is 50 watts in use, 5 watts in standby.

All digital audio/video data are upsampled to 176.4/192kHz using COS' own 32-bit algorithm to bypass their DACs' on-chip SRC; then buffered by one second; finally reclocked with a <1ps crystal oscillator. Two-stage power supply regulation assigns discrete toroidal transformers to the digital and analog circuits. A dual mono layout dedicates separate power regulation, filters, DAC chips and volume control to each channel. The current outputs of the 24/192 stereo DACs are combined into mono feeds for improved SN/R and "manually tuned and matched for 6dB lower distortion than their specification". For those tired of the DSD hype, the D1 remains mum on the entire subject. As the rear panel shows, the buffer can be defeated (recommended for video to better sync sound and picture); and the USB input can run as USB 1.0 or 2.0, with the former requiring no drivers for Windows.

Time to learn more about COS. First off, it's short for connoisseur of sound. Then, "Stephen and Oliver are college school mates with more than 20 years of experience in engineering. They are the founders of a public company in Taiwan. Stephen is strong in product design and planning, Oliver specializes in product R&D. Together they form a good team. C.C. with his finance background joined the same company later as president. He is keen of hearing and can perceive sounds even with subtle differences. The three share a common interest in hifi and decided to start COS three years ago. Here Stephen is in charge of electronics, Oliver is responsible for the digital filter and C.C. is the resident critic to detect areas for improvement. Next in our R&D pipeline is the H1 planned for a summer 2015 release. It will be an amplifier to match the D1. The systems of our three founders you asked about and the one we use in the office are as follows."

source Chord DAC64 Chord Blu, Chord DAC 64, Marantz CD16D Mark Levinson N°. 30.5 + 31.5, Marantz SA14  
preamp Mcintosh C42 Mcintosh C500c, Supratek Cabernet, Placette Audio passive linestage Mark Levinson N°. 32 Goldmund Telos 600
power amp Mcintosh MC352 Mcintosh MC352 X 2, Densen DM-10 Boulder 2060  
speakers Sonus Faber Cremona, Tannoy Kingdom 12, Dynaudio 6 Sonus Faber Stradivari Sonus Faber Stradivari Sonus Faber Amati
power delivery   Aray First Cry Aray First Cry  
turntable Nottingham SpaceDeck   Nottingham Dais  
cartridge Goldring 1042   BenzMicro LP  
phono amp Lehmann Black Cube   Lehmann Silver Cube  
headfi amp   HeadRoom Maxed Out    
headphones     Sennheiser HD600, audio-technica ATH-W1000    
cables Van Den Hul Van Den Hul Van Den Hul Van Den Hul

Maggie then wanted to know whether I'd use my own power cord. If not, she'd source an adaptor to suit Switzerland's own 3-prong outlets. Very professional. Most far more established companies ship me utterly useless Schuko cords. I told her not to bother. I'd use my own since past a wall adaptor I'm on US-style plugs. "There are three things I would like to mention before you start the audition. 1/, the D1 will need 10 minutes to warm up before it reaches its ultimate performance. 2/ If you decide to open the machine, please ensure that you don’t touch the four white wires at all. These are manually tuned and matched so the performance will be greatly affected even if they’re slightly moved. 3/ When you put the spikes on, please ensure that you place the D1 on its side. Flipping the machine upside down will obviously put pressure on the exposed volume knob." These were all perfectly sensible requests, no 500 hours of break-in demanded before one was allowed to come to any conclusions. Was COS really shorthand for common ordinary sense? Wicked! Tracking the shipment's progress, I saw that its point of origin was Taiwan's Hsin Tien City before it made tracks to mainland China in GuangZhou, then Europe via Köln and Basel.