Hi and welcome to ASR.I can confirm that I also get the "scratching" noise with my JM20 when waking it up, however I don't hear any hissing or popping. Weirdly though, in windows it shows up as a MBQuart MB20P? (I got it from what seems to be a reputable seller online). On the outside it looks exactly as pictured in this thread.
If I'm not mistaken, this DAC has a high/low gain mode. Is there any way to adjust that, along with hardware volume on Windows?
Yes, that brief "scratching" every time it resumes from sleep mode is the only minor issue I can blame to the dongle.
MBquart MB20P is essentially the same unit under different brand, I connected the JM20 to Windows just briefly long time ago, I don't remember how it was recognized but for sure not as MBquart, i would remember it, maybe some mishap in reseller stocked items...