I don't know if this will help anyone, but I could not get my music server to connect properly to the Gustard R26 via the I2S input. It connected, but PCM files displayed as DSD, and sound only came out of the left side with great distortion. I tried five different hdmi/I2S cables and nothing made a difference. Finally I bought the Gustard U18 to make sure the I2S input was working on the R26, and it was working. So my only solution was to build an I2S cable and try all the combinations to determine the correct pinout. I tried all combinations and nothing made a difference. Finally, I read somewhere about shorting Pin 15 with Ground, so I tried that on the connector side closest to the dac, and no difference. Last option, I shorted Pin 15 (the PCM/DSC flag pin) with Ground (Pin 17) closest to the streamer connector, and it worked! So, long story short, if you are having an I2S pinout issue, it might be that shorting Pin 15 with Ground (Pin 17 in my case) will do the trick. Unfortunately the R26 doesn't have any pinout options like Denafrips, so you are kind of stuck unless you order a special cable or make your own. I'm including picture of how to make the I2S cable if you need to. My cable was only to try different pinout options, so it's not complete and I wouldn't use it as a permanent option. By the way, this was my first I2S cable, so it's not pretty, but it got the job done. I tried adapting a regular hdmi cable and that was a disaster. It was much easier, about an hour of work, to make your own cable from scrap.
