I may be getting totally confused and misunderstanding what the Matrix X-SPDIF 2 but is it fair to compare it with optical ethernet FMCs for the purposes of isolation?
My current understanding is that the two approaches are this:
- music server -> USB cable -> X-SPDIF 2 -> I2S cable -> DSD DAC
- music server -> ethernet cable -> router -> ethernet cable -> FMC -> optical cable -> FMC -> ethernet cable -> DSD DAC
Assuming power supplies are equal, which do people feel is the better approach.
As always, thanks so much for the upcoming education. 
The Matrix isnāt really an isolation device: itās a well designed and built USB -> AES3 / S/PDIF / TOSLink / I2S converter. I find this function to be valuable in my system and itās gravy that I also get better sound quality in my system. The Matrix (possibly with an external power supply) is all the tweaking that many people think they need with USB.
Iād say that the Matrix helps most peopleās systems sound quality enough that they donāt feel that the Bridge (even well tweaked) has an inherent advantage compared to USB. This frees them to pick the UI they want or, for example, the infrastructure they want (USB doesnāt support nearly as long of a cable as Ethernet does.)
To me the biggest difference in the two options you show would be the user interface. Personally I donāt like any of the UIs that Iāve seen for DLNA / UPnP systems, they donāt let me navigate my music collection in the manner to which Iāve become accustomed. On the other hand probably most people like those interfaces better than the nerdware I use (foobar2000).
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Thanks, @tedsmith!
Iām a fan of roon so if I went down the Matrix route I would run roon on the music server and output directly from itās USB to the Matrix and ultimately into the I2S port on my DAC. I think would work and would negate the need to invest in FMCs and potentially one additional LPS. (2x FMCs vs 1x Matrix).
The only downside I see is that Iād need to have my music server in the listening room.
I think that would be the best approach assuming I can mask any audible fan noise from the server (could do fanless NUC of course)?
I find Foobar2000 to be the absolute best windows media player whatsoever! I have tried them all.
Hi @tedsmith I see the newer X-SPDIF3 has isolation
Have you thought about upgrading to the newer Matrix ?
Here is X-SPDIF3 tech info from Matrix website:
Compared with the previous generation, the IIS-LVDS output isolation is added, which completely isolates the digital output from the ground wire of the USB end, and bids farewell to the annoying noise of the USB front end. In addition, it supports up to 32Bit/768kHz PCM signal and 1Bit/DSD512 signal output, achieving an excellent output quality from both PC and mobile devices.
Iāve been putting off getting one. Iād really like to get one, but the Matrix 2 is serving my purposes now. I have to talk myself down about once a month 
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The website states power requirements āUSB bus power supply: 5V/1000mAā
That doesnāt make any sense.
More than USB3 spec and it isnāt even a USB3 port like X-SPDIF2
Using USB-PD the device can request up to 3A using a standard cable. The docs talk about using an USB OTG cable and OTG does optionally support USB-PD and whatever the other power delivery over USB spec is out thereā¦ USB 2.0 is all thatās needed for USB Audio 2.0 or USB Audio 3.0.
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Ok Iāve asked Matrix on their forum, lets see if they mention USB-PD too
X-SPDIF 3 - USB bus power spec is 1000mA
I suspect youāre right of course
Many computers now have Thunderbolt / USB-C ports that can supply more than 900mA at 5Vdc
Matrix have confirmed in my thread linked above that USB 2.0 port is sufficient (500 mA)
At least it seems that way
No requirement for the 1000mA they specify on their website
