Thanks @greg_f  I really appreciate the info and support.

The CA thread is a good resource, although probably more technical than I need.  My goal is to try a better SFP module to see if it will improve the fibre feed to my Lumin U2.  I'd read that Finisar modules were recommended by many on this site.

I'll reach out to Cisco to see if I can get the specs for my Catalyst 2960 switch, and see what modules might be compatible -- and which might offer a SQ improvement.

Many thanks,

JAMES.

@jimboman James, yes the Finisar modules seem to be one of the most popular. Get LC modules perhaps something like FTLF1318P3BTL or if you like to try AOC (Active Optical Cable) then the Cisco SFP-10G-AOC5M or similar, but please do check compatibility at both ends.

@jimboman

I have bought two of this cable ( LuminX1 and Lumin L2) with ´´ APC Optical Fiber edition ´´ Still waiting for the delivery

In replacement of ´´Melco C1-D20 SFP+ Direct Attach Cable ´´

https://www.adark.co/collections/project-constellation-fiber/products/copy-of-afterdark-project-clayx-constellation-sfp-module-for-audiophile?variant=39631937994870

Thanks @greg_f .  I am using the Finisar 1318 you suggested.

I tried bypassing my Cisco Catalyst 2960 with a cheap Mokertek FMC I had lying around, and the Finisar modules work (including one in the Lumin U2)!  This confirms that the compatibility issue was with the Cisco switch.

I find the sound quality to be just a touch more 'full', particularly in the low bass region, with the Finisar modules.  It's a subtle difference, but for the cost, worthwhile IMHO.

With that in mind, I'm wondering what people are recommending for FMCs with good SQ?  @ozzy @audphile1 @tksteingraber @maxwave  (and others) care to chime in?

Best, JAMES.

@jimboman Perhaps an Etherregen or an Sonore optical Module? How are you connected to the Cisco 2960? What is your network structure?