When we measured the audio noise during playback we found some
non repeating random noises , when we investigated this , we found
it was from the Ethernet port when the player app was downloading data,
we also noticed noise when using WiFi while streaming data.
We explored various options to reduce it , One to shield it the analog section,
the second would be to reduce as much unnecessary
stuff from running when we are playing back a track. For example
the UPNP server if running answers to any device on the network
querying for it (SSDP).
Our software stack does not run any unnecessary BG daemons till
the user starts it. So unless you are in the UPNP player mode the
daemon is not running in the background. Same for other Player
daemons too.
Second important thing we found that reduced the noise during playback
of network content (NAS/UPNP Stream) or even USB content, is to download it to
a RAM disk and play it from there. There is a small delay during startup for
downloading the track but more than makes up for much better listening
experience. There are No IO operations , no buffering etc, that happen when we playback from the RAM disk so much cleaner sounding playback.
We have an Option to turn on “Download Before Play” in Settings menu.
Finally we have taken great care to isolate the power supplies and
shield transformers from analog sections etc.