Things have moved on quite a bit so I suggest you look at the Allo USBridge signature. I have it on good authority this is significant development.
https://allo.com/sparky/usbridge-signature-player.html
I went through a period with NUC Roon server and endpoints but then discovered this little gem, a modified simple SD card player with I2S output. It’s basic but overwhelmingly the best, most natural sound I have found to date.
http://www.tirnahifi.org/forum/viewtopic.php?f=15&t=4541
PS Yes I did get my original Sparky/Dietpi/McDualXO/McFifo to work outputting I2S and used it for a while but its been superseded by other things I mentioned…
Thanks Patrick. I have an original sparky USBridge, and a kali,piano2.1 setup with Volt (not installed currently) so I’m familiar with the Allo kit.
Trying to find a way to redeploy my dam1021 that I repaired (hopefully) anyway enjoy your music…I find I. Doing that more than wanting to diy these days 
Managed to get it working on a RPi 3b with just the 3 i2s lines and grounds connected. No 3v3 or other connections to the Soekris.
Now I’m trying to get it working with Ian Canada’s I2S isolator and DoP to DSD board…should be interesting. Also needs a couple of 5v supplies to add to the mix.
Nice work 
! It’s probably best to get the 3 I2S lines as short as you can… How does it sound?
Yes the wires are 150mm I think but today I found some 100mm ones so will try those with isolatorpi.
@spockfish done a feedback for you Harry, just to make sure there is no better HAT setting I could use and or see if there is any tweaking possible to get past 24/192 see 5d037060b8d206e1
There is no need to use isolator - all i2s inputs of DAM 1021 are galvanic isolated (SI8620BB)
There is if you want the dop to dsd conversion, but I have given up for now and just upswing with the Flirc.tv 3b case over the top to give some cooling and shielding too
Made setup with a NanoPi NEO Plus2 + PSU from Meanwell, with USB to the Amanero, and then to I²S on the Soekris. This is playing DSF files to 352.8 kHz/ DXD level.
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you are using the unbuffered line outputs for the RCA?
**Both balanced and RCA, I have a Preamp that can do both, so I can listen to the channels and hear no big difference.
Am I right in assuming the only way to get anything above 24/192 from Pi4 I2s>Soekris is by using the Amanero?
Sorry, totally new to Roon, trying it out as a different option to Moode.
That might be the best way
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I have used the Derone with Bravo chip SA9227, works fine with Linux and Roon, there are also drivers for Windows cost are then € 28 AliExpres.
Also possible with S/PDIF output, where I use it now.
Thanks bro, I got one to try, maybe will get it to do DSD which I haven’t got working on the rpi.
Hi Hans, Ineke,
I just read your reply here. Would you be so kind to verify the ali-link or verify my found product. Did you get this board running with a raspberry pi too? Could you also tell me if or how you use volume control in Roon with the dam1021? Thanks (Looks like you’re Dutch so you can also reply me in PM in dutch 
)
Hi Maikel, from Bangkok? 
I have the interface with no problems in combination with the Friendlyelec Neo and Roon. I dont use the RPI, there is maybe a problem with the frequentie that is given by a standard RPI.
link ali, SA9227 Usb Interface Dac Board I2s Pcm 384Khz Dsd 128 Digitale Interface Gratis Verzending|DAC| - AliExpress