Lumin U1 to PS Audio Direct Stream, via USB with Intona and iFi Micro, is the best I’ve heard so far.
Others I’ve heard:
Roon/ROCK on Intel NUCi5 > PS Audio DSD;
Synology NAS/Minimserver > PS Audio DSD;
Logitech Transporter > Audio Note DAC;
Squeezebox Touch > Audio Note DAC;
Mac Mini > Ayre QB-9
Transporter > AN 4.1 DAC is prob close behind the Lumin/DSD.
There are others I just don’t recall all the combos.