Sound quality differences between NAS units

[DavidL]

As other posters have indicated I suspect the differences heard are due to variations in the level of noise/interference transmitted with the ethernet music packets. When I bought a stand-alone renderer (the Sonore Rendu) I was told by the designer that it had built-in isolation, however because it was inexpensive to do I added external optical isolation in the last ethernet link to my DAC and this made a small but audible improvement in sound quality. I found this surprising as I have a wireless bridge between my NAS, computer etc and the hifi equipment which I thought would prevent any related noise/interference reaching the renderer and DAC. I can only assume that power supplies etc local to the hifi equipment was introducing noise/interference. The mains for the hifi is a separate dedicated spur from the rest of the household mains (including computers, NAS etc.), and I use linear power supplies for the hifi kit.