@amirmBlack Lion Audio White Sparrow DAC Measurements
I started my testing with S/PDIF connection:
View attachment 205764
Very surprised to see such a jungle of spikes around our main tone which likely indicates jitter. There is also power supply noise which may be the source of said jitter (or some of it). I should note that on power up, one channel had much more distortion which pulled SINAD down to 90 dB but it climbed up after 1 minute of warm up.
why do you think its power supply "noise" ? I don't see any fundamental 60hz (or 120,180hz) spikes ?
That looks like jitter. Is the jitter frequency close to 60hz ? If so it could be emi induced jitter from the transformer or nearby ac lines. or maybe just physical vibration of the crystal from the transformer if too close or not isolated properly. Can you open it up and show us the insides ?