So, presumably, without EDO, Roon would convert DSD to PCM and 192/24 to 96/24?
When addressing compatibility between content and a device, Roon cuts the sample rate in half until it reaches a rate that the device supports. So, for example, an SB3 that supports only 44.1k and 48k will play 192k content at 48k and 88.2k content at 44.1k. DSD content (which inhabits sample rates that are integer multiples of 44.1k) would all play at 44.1k.
Likewise, if playing to a device that doesn’t support DSD (either native, or encapsulated), the DSD content will be converted to PCM. For the most part, Roon’s idea of whether a device supports DSD or not is something managed in Roon’s settings.
None of what I just explained is specific to Squeezebox–the same logic applies to all outputs.
And with EDO, it will do native DSD and 192/24?
From Roon’s perspective, EDO just causes the Touch to support 176.4/24 and 192/24 in addition to the configurations that it supported from the factory.
When DSD64 is encapsulated as DoP, it is carried within a 176.4/24 PCM stream. So EDO creates the possibility of transmitting DoP-encapsulated DSD64 to a DoP-capable DAC via the coax-out on the SB Touch.
So, if you have a Touch with EDO, you can go into Roon settings and choose “DSD over PCM” as the “DSD Playback Strategy”, just as you would on a local audio device.
One thing I’ve never been clear about: will a Touch with EDO send 192/24 over its optical/coax output? Or DSD?
S/PDIF is explicitly a PCM interconnect. I’m not aware of anyone carrying “naked” DSD streams over S/PDIF without encapsulating them using something like DoP.
The Touch, even with EDO, has no awareness of DSD–from the perspective of its hardware/firmware, it’s playing a 176.4/24 PCM stream. It’s up to the DAC that you’ve plugged into the Touch to recognize that the incoming PCM stream is DoP-encapsulated DSD64 and handle it properly.