This is my build. It’s a streamer built on the StationPi. FifoPi with Acusilicon clocks, ReclockPi and HDMIPi sending out an I2S signal to my dac. The dirty side of the Pi is powered by the LinearPi and the FifoPi is powered by a 3.3v LifePO4 mini.
I’m really happy with it, but I can’t leave it alone, hence the itch to build a full dac stack.
In case you missed it, here’s my current DAC/Streamer build in a thread over at DIYAudio
Hi AudioMike,
I’ve just taken delivery of -
FiFoPi Q7
HDMIpi MkII
Monitor Pi
PurePi 5V+3.3V
LinearPi Solo
to match with my RPi 4B and Denafrips Pontus 2 DAC.
I want to just use RoonBridge as I have been doing with my hifiberry-digi. Can you tell me what you used for the dtoverlay and any other settings you used to get it going or if this is even possible?
I’ve tried dtoverlay=i2s-dac and hifiberry-dacplus
Thanks.
I know this is old thread, but I’m wondering how you did this - having 2 separate endpoints, point to 1 DAC, and switch between the two. I’m trying to get the same functional with my stack that includes;
PurePi II > RPi 3 > BridgePi > Combo768 > IsolatorPi III > MonitorPi > DAC HaT
I can get one or the other going, but I can’t get it change to the other when I try to change to it. I know I’m using newer hardware from Ian, so your solution may not be applicable. Maybe what I’m trying to do cannot be done without the newer ReceiverPi DDC. This is not an option I will use/need everyday, but I do like to build-in the capability if it’s possible.
I’ve been building RPi endpoints for years, but this combination of kit parts are messing with my mind. 
Rick
Hi Richard, which Pi, distribution and hardware options are you using?
Mike
I’m using an older Pi 3B with the latest version of Ropieee for the 3B. If you’re referring to my stack - it was listed below. In Ropieee, I’ve got the USB enabled, but it’s not detected. Is that what you meant? No WiFi enabled. Does that help?
Edit: It just dawned on me that the USB Audio in Ropieee is used only for an external DAC, so that doesn’t apply to my use case and is irrelevant. I’m now testing with an RPi 5 and have removed the IsolatorPi III and the MonitorPi. Still the same results. Unable to switch between the two endpoints.
I’m not overly familiar with your hats but generally only one output hat will work at once. My hat outputs iic, aes & spidf simultaneously which in turn go to their respective inputs on my dac. USB can also be active, but you need to pause your Roon playback when switching to / from. Once you around that, you can select USB as a Roon end point and you hat as an endpoint…
If I understand your post, you’re using an external DAC? Or, you are using a TransportPi? That’s would make a big difference. I think in my case the software is competing with each other, and who gets to the I2S buss first. There’s no hard switch, and even though I select the Combo768 (USB), endpoint in roon, if I switch to the DAC HaT (over I2S) it won’t switch. I don’t think roon discriminates that both endpoints are coming into the same physical hardware stack. (1) USB (Combo768), and (2) I2S (network). Oh the joys of having too many options!
Edit: I simply may not be able to achieve what I’m trying to do, without additional hardware. ie. the ReceiverPi DDC.
Just build another pi, and dedicate one to the USB-interface and the other to your DAC HAT. You are complicating things to an unnecessary degree! 
…
And, i am convinced that the USB output choice in Ropieee is referring to the USB port on the Pi itself, not the HAT.
Edit: I just realised that the Combo768 is a USB INPUT, not sure what you are trying to achieve and therefore disregard my post…
As I mentioned above, at this point I don’t believe it’s achievable with the current hardware I’m trying to use. I’m an avid music lover, but I’m also a tinkerer that likes to be challenged with builds - especially with this one using some leftover kit parts from other builds. 
Ian’s boards offer a level of music reproduction that are suitable for a wide range of enthusiasts - and a pile of hardware at your disposal. Having said that, many have found that some things simply don’t play well together, or there may be software, that supports this, or that option. But, he continues to improve and innovate with new and/or upgraded products that address new features and functionality for the system builder.
Roon has been my friend over the past 5yrs on the software side, that simply just works with a ever growing hardware list - both commercially and kit hardware available to the diy’er. Most of Ian’s hardware is trouble-free and software agnostic that makes the ‘fun factor’ and experimentation easier to achieve. 
Rick
Well aware of IAN Canada’s stuff, have a few.
Still dont understand what you intend to accomplish, but a way forward would be that you draw up a flowchart of what inputs/outputs you wish to materialize.
