I received the TP-Link CM100M units yesterday and installed them between the switch and the Directsream DAC. I selected all the dip switches in the up position and it fired up without any issues. After listening to my standard reference files, including Tidal streamed via Roon, I came to a few conclusions:
Playing vinyl DSD rips showed the optical isolation to be a little more dynamic, just a touch. Not jarring by any stretch. The music was a little more palpable. I’m not sure I could pick it out in A:B comparison.
Playing hi res 24/96 files, RB rips, and DSD downloads also pretty much followed my experience with the DSD vinyl rips. Just a little more dynamic and hopefully not expectation bias.
Things got interesting when I listened to Tidal streams via Roon. I immediately noticed the music was more palpable than before. It was like the improved dynamics were on turbo. Percussion was more crisp and cymbals more lifelike. In particular listening to Nickel Creek, Chris Thile’s mandolin strikes on “When in Rome” seemed to jump out with more energy and all the instruments had more distinct percussion and separation. This was not a subtle difference. I could easily blind pick the fiber isolation from the non-isolated.
So why is this, I wonder? I can only ascribe this to the fact that streaming is more susceptible to upstream noise than my archived recordings, I guess. Just to see how good Tidal files were sounding, I compared The Doors Morrison Hotel DSD 64 from HDTracks to the Tidal version and could honestly not hear a difference. Not that there was a huge difference before, but now there was none. The Tidal version sounded great. And just as importantly, I have not experienced any momentary distortions I would occasionally hear while streaming. I wishfully attributed this to my non-shielded CAT6a ethernet cabling picking up RFI from the mess of cords I have behind my system. Now the optical fiber crosses the power cords, etc, and is now theoretically more immune to such effects. Theoretically.
So I’m very happy with the fiber isolation. One quirk I noticed was while listening to DSD 128 (or which I have a lot of vinyl rips) to the Bridge. Roon apparently negotiates with the DS DAC and converts DSD 128 to PCM 352 automatically and then to 176. This has gone on without a hitch without the optical isolation. But after isolation, I get a harsh digital noisy sound obscuring the underlying song. I had to go into Roon and enable DSP and down-sampling to DSD 64 to make the digital noise go away. This can’t be a problem of bandwidth, I would imagine. It’s not a processing issue since it can transpose into DSD, which takes more processing power than the conversion to PCM 176. I have no clue why that is. Weird. More experimentation is needed to figure out what the cause is.