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Fiber-optic module

Reviewer: Srajan Ebaen
Financial interests: click here
Main system: Sources: late 2020 Retina 5K 27" iMac with 40GB RAM and Ventura 13.4, 4TB external SSD, Audirvana Origin, Qobuz Sublime,
Singxer SU-6 USB bridge, LHY Audio SW-8 network switch with SOtM iSO-CAT7 isolator, Sonnet Pasithea DAC; Active filter: icOn Gradient Box 2; Power amplifiers: Kinki Studio EX-B7 monos, Goldmund/Job 225; Headamp: Cen.Grand Silver Fox; Phones: HifiMan Susvara; Loudspeakers: Qualio Auido IQ + sound|kaos DSUB 15 on Carbide Audio footers, Audio Physic Codex; Cables: Complete loom of Allnic Audio ZL; Power delivery: Vibex Granada/Alhambra on all source components, Furutech RTP-6 on amps, Furutech DPS-4.1 between wall and conditioner; Equipment rack: Artesanía Audio Exoteryc double-wide 3-tier with optional glass shelves, Exoteryc Krion and glass amp stands; Sundry accessories: Acoustic System resonators, LessLoss Firewall for loudspeakers, Furutech NCF Signal Boosters; Room: 6 x 8m with open door behind listening seat
2nd system: Source: Shanling M3 Ultra, Soundaware D300Ref SD transport, Cen.Grand DSDAC 1.0 Deluxe; Preamp/filter: icOn 4Pro + 80Hz active filter, Vinnie Rossi L2 Signature w. ER50; Amp: Enleum AMP-23R; Loudspeakers: MonAcoustics SuperMon Mini, Dynaudio S18 sub; Power delivery: Furutech GTO 2D NCF, Akiko Audio Corelli; Equipment rack: Hifistay Mythology Transform X-Frame [on extended loan]; Sundry accessories: Audioquest Fog Lifters; Furutech NFC Clear Lines; Room: ~3.5 x 8m
Desktop system: Source: HP Z230 work station Win10/64; USB bridge: Singxer SU-2; Headamp/DAC: iFi iDSD Pro Signature;  Headphones: Final D-8000; Active speakers: DMAX SC5
Upstairs headfi/speaker system: Source: smsl Dp5 transport; DAC: Auralic Vega; Integrated amplifier: Schiit Jotunheim R; Phones: Raal-Requisite SR1a; Active DSP speakers: Fram Midi 120
2-channel video system: Source: Oppo BDP-105; All-in-One: Gold Note IS-1000 Deluxe; Loudspeakers: Zu Soul VI; Subwoofer: Zu Submission; Power delivery: Furutech eTP-8, Room: ~6x4m

Review component retail: €TBA

No sooner had the virtual ink dried that more audiophile mischief was afoot. I'd put the COS S10 LAN distributor aka network switch review to bed to request the usual call-tag pickup. Their Stephen Gong demurred. "Do you mind keeping it for a few more days? We might shortly have an acceptable fibre-optics streaming module for the D10." I didn't have a D10; and already covered the original then v2 in two reviews. "How about we send you a D10 with copper streaming module and an alternate fibre-optics module? This would be just to compare the two modules."

This was about isolating one of the S10's fibre-optic ports to mandate an equivalent receiver; very much like digital Toslink cable needs matching send/receive ports. COS had temporarily shelved a standalone fibre module which would bolt light-based network transmission to any RJ45-fitted machine. To test their superior port in the switch mandated a Lumin-type streamer with built-in such module. In the current COS catalogue only the 5-in-1 D10 has that option. Hence Stephen's proposal to send me one of those to shake hands with the SFP port on the switch I still had on hand. I accepted the mission before the invite would self destruct.

If you're still hazy over fibre-whatniks, affix an eye to the back of this Lumin. Between USB and network port sits an optical version. That's what this gig will zoom into vis-à-vis the typical RJ45 entry. Since none of my decks are fitted with SFP fibre, COS had to cover all my bases.

Here comes the S10 which on the far right of its back panel sports stacked fibre-optic ports. Now the scene is staged. All actors are on their marks. Whilst their dialogue hasn't been penned yet—these are pros who make up their lines as we go along—you just know what comes next.

The director shouts "action" in all capital letters. Of course yours truly never shot a digital movie in fibre optics before. Perhaps better whisper in all lower case. What to expect? I knew that for his Black system, Bel Canto's John Stronczer has for already years proposed ST-fibre transmission for best performance. I'd read that aside from Lumin, Melco too support the SFP optical standard. Even my resident SW-8 switch's bigger brother called SW-10 adds two such ports. But aside from anecdotal footnotes, to me this whole subject was still very esoteric. Time to get with the program. Now reader Michael Fanning dug me a hole: "I enjoyed your review of the COS Engineering LAN distributor and found it intriguing that they're now keen on having you test its fibre-optic streaming module for the D10. I employ a fibre-optic connection between Lumin X1 and etherRegen switch and never thought of using an RJ45 copper connection. I figured if Lumin spent extra coin on a fibre-optic connection, it must by definition be at least a smidgen better. I'll be curious whether COS specify exactly which SFP connection they recommend or are agnostic on the subject. There's lively back 'n' forth on AudiophileStyle and other fora about multi- vs. single-mode transmission¹ and who makes the most audiophile-friendly SFP module (Finisar from Small Green Computer get much love for example). Once transmission style and SFP modules are identified, which optic fibre transmits most faithfully? Do I hear a shoutout for Corning ClearCurve? Of course the bits-are-bits crowd is aghast and says that mode, module and fibre don't matter. I warn you in advance that as you begin your journey, this particular rabbit hole is quite deep!"

Prototype S10 | prototype SFP module for D10

¹ Single-mode fibre transmits a single light mode, multimode multiple modes simultaneously. A single-mode optical core is 9µm thick, a modern multimode core 50µm. Single mode enjoys higher bandwidth and longer transmission distances and in OS2 grade supports 100GB data density or 8K video across 10km.