Connecting Volumio on RPi 4 to Home Stereo System (Cirrus Logic CS4398 DAC)

This is very much a novice’s question. I bought a Raspberry Pi 4 with the idea of using Volumio to stream music from a Qnap NAS to my HiFi system over an Ethernet Home Network. I planned to use the built in DAC in my Marantz Tuner (NA7004) which can be connected to the RPi via USB B. The DAC is a Cirrus Logic CS4398 and is not in your supported DAC list (needless to say I did not know this when I set out on this plan; I naively thought any DAC would do!). Now I am beginning to think that this is not possible. Certainly a test of the set up after having installed the Volumio image on the Pi produced no sound! However I would be very happy to discover that after all it is possible. And, if it is, what settings should I be using in the Volumio GUI?
I hope someone can help. Thanks in anticipation.

Only skimmed this thread, but this seems to be someone using the DAC back in 2018. You might like to do some more searches yourself.

Thanks for your reply chsims1. I looked at the thread you suggested and from what it says it looks as though it is possible to connect the RaspberryPi directly to the Marantz DAC via USB A to USB B. So the next question is what Audio Output settings to choose in the Volumio setup page. I’m guessing that I2S DAC should be set to “Off”. But then the only alternatives for Audio Out are “HDMI” or “Headphones”; no setting for “USB Out”! So where to go? Maybe simply by plugging the Raspberry Pi into the Marantz DAC and turning on the Pi volumio automatically finds the USB output? Also what about the settings at “General Playback Options” and 'Volume Options" - what to do there? I am all at sea. Any advice? Thanks again and I look forward to hearing from anyone with more knowledge than I have, ie. probably anyone at all on this forum.

Well for starters, yes you definitely need to connect the RPi to your DAC, and hopefully it will recognise that there is a valid USB out. As to the rest of your options, it will depend on the capabilities of the DAC, and you will need to try and see what happens.

When you connect your RPi to the Marantz, the USB DAC should show up in the playback options.
Start with switching the Marantz to USB input and then boot the RPi and from the playback options choose whatever USB Audio name it shows.
In case it does not work, try switching the usb port on the RPi.
When it still doesn’t, you will need to make a log after doing this, preferably from a fairly fresh start.
Also check whether you can/need to set the Marantz USB interface to Class 2 Audio (which is the case with some amplifiers I know, like the Cambridge).
The NA7004 seems to be a Class 1 Audio device and cannot be configured to Class 2

Thanks to both chsims1 and gkkpch I now have Volumio working via the Marantz NA7004 DAC. Sounds great through my HiFi system! I couldn’t have done it without your help. Regards and thanks again.