Sound quality differences between NAS units

[Mike48]

Though I have only one NAS (a Synology, as it happens), I don't doubt the difference. I have heard this before and seen reviews as well. I think Simon posted comments along these lines, too. From an engineering point of view, I find it interesting and disturbing.

Back to the original poster's question, I wonder

1. What, if anything, might be done in software to minimize this difference?
2. How much does this depend on the renderer and DAC?
3. Is the effect more pronounced with an Ethernet or a Wifi connection, or does it make no difference?
   

Mike