Two questions for
@Christiaan Punter or
@Taiko Audio:
1. With the DCD and Router/Switch not being galvanically isolated from the O/IO - how important is it that they closely share the same AC ground?
How many people have the DCD/Router/Switch on a separate circuit vs the same circuit as the O+I/O?
2. A Roon extension is available to allow volume control of my preamp from Roon (it connects to Home Assistant and triggers an IR blaster to send Vol up or Vol down signals), allowing me to control volume directly from Roon without switching apps or grabbing the remote.
Any known detrimental effects from running Roon extensions? The Home assistant instance does poll Roon for song/playback position and status on an ongoing basis, though probably no different than having another Roon client connected to the Olympus Roon instance...
As MarkusBarkus mentions, it's best to use the same phase. Further, to avoid ground loops, it's best to use the same AC ground. Generally speaking, I find that using the same single ground for the entire system yields the best coherence and focus. Conversely, when sourcing ground via different cables and from different spurs, this tends to have a blurring effect. This is not an issue for galvanically isolated devices like Routers, which are frequently located in other rooms and on different circuits. When you have multiple 100% identical spurs, the outcome can differ, and there are other exceptions, as no two situations are alike, so it may be worth experimenting.
Regarding Roon extensions, basically, the more Roon does, the more network traffic it generates, and the more audible its effect. Then again, with Olympus, the Router, Switch, and DCD, we have various measures in place to minimize Roon's influence.
In cases where I disabled Roon volume control for a DAC, this has often been audible, even at 100% volume. However, in such cases, it is hard to determine whether the impact is due to Roon traffic or processes within the DAC. A preamplifier could behave similarly or differently, but neither Emile nor I have a preamp that allows this, so we have no first-hand experience with it.
If or when you decide to test this, I would be interested to hear the results.