How to get DSD working in a networked (Roon) setup?

Thank you for your reactions

@lordmelton : a DSD album on a usb stick, not SACD

The MP doesn't see DSD (*.dsf) files, so I can't plug in and play. That's exactly the issue.

@jazzman7 : They are on my NAS, but Roon transforms it into PCM and downsamples it. No purpose in DSD128 or DSD256 files if they're downsampled.

@bhoage : When you follow the signal path, is Roon downsampling? I have the *.dsf files, but it's brought to my speakers as PCM and downsampled. Thanks for sharing that link!

Thanks for getting back to me.

@jazzman7 : It's afaik what happens - Roon downsamples as I'm now relying on a network infrastructure rather than a USB connection with a PC. I'll take a screenshot this evening. 

Indeed - only through the "USB DAC" DSD files can be played. Furthermore, depending on the USB receiver used, there might be a limitation on the quality as well. 

I really new to DSD. But indeed - having done more research and with the answers received I started to look for a PS Audio DirectStream with Bridge II (new model of the DS is out so sharp prices second hand) or a Lumin Mini U2. Over time, I hope to migrate to the T+A PSD 3100 HV (it's delayed) as it will also support DSD256 over LAN. We'll see :) 
Your summary thus seems correct: DSD capable, Roon capable, USB bridge. Would you happen to know such a device?

@lordmelton : the unit plays flac without an issue. I have the same album in flac/DSD to compare, the flac was visible, the DSD simply wasn't. It only plays native DSD through the "USB DAC", and then it functions like a sound card. So yes - it does native, but only through the USB DAC receiver.

Thanks @yage - I'm like 80% convinced I've changed that 10 times to DSD but that it jumps back. I'll pay more attention to it. The "DoP for Converter" is unchecked.

So I plunged the deep end and turned my (work) laptop into a audio player. Installed the T+A USB driver, installed Foobar2000, installed the AISO & DSD components, etc. I found the right USB cable, connected my laptop and after some fiddling was able to play DSD files on a USB stick. As the T+A still kept showing PCM as output, I really start to wonder what I'm overlooking :)

Anyway

@yage : I did indeed, it was the part I wanted to avoid as my (gaming) rig is literally on the other side of the house and the only laptop is from work.

@erik_squires : The streaming works, I uploaded a DSD album to Roon and it plays, but with downsampling (Roon literally says "downsampling", so I assume that's what it does).

@bhoage : I'm trying to play DSD256 / DSD128 files so I assume it's downsampling if Roon only plays DSD64 and (ii) literally says "downsampling" in the signal path. I'll remember to make a screenshot from it next time.

@jazzman7 Thank you for your input, going to take a look at such a setup. 

@lordmelton The SACD and DAC part are separated in the unit. It can play up to DSD512 but I didn't manage that yet. Coming close now connecting my laptop to it, but it still moves to DoP.

Dear all, just an update. I got it working but you'll never guess how.

I ran into the guide below, explaining how to install a music streamer on a Raspberry Pi4B. I had one laying around by accident. So I installed Volumio on it, bought a higher end 2m USB cable and it plays bit perfect DSD256 to my T+A MP 3100 HV. It's a bit weird to see a 150 USD solution dangling behind the T+A, but it works. 

To make it clear: with this Pi based solution, I can play (at least up to) DSD256 from a USB stick plugged in the Pi, over USB to the "USB DAC" port on my T+A MP 3100 HV. Config was too easy to be true, certainly compared to Foobar2000. 

Thanks for your feedback @erik_squires . I've a NUC for Roon (the ROCK setup), doesn't it require more power than a Pi4B can deliver?

The challenge here is that my DSD collection is very limited and kept on a USB stick. Would Roon see the stick and be able to push DSD to the "USB DAC" gate?

I ordered a 4-pack of micro SD cards so could give it a go :)