Update. I found the JitterBug to be very effective when used with my Windows 10 PC desktop. The difference in the upper mids is startlingly evident. Without JitterBug, the complex passages of multi-instrument recordings sounded much more wiry and borderline harsh. Inserting the JitterBug between the PC and USB cable feeding my DAC, I was able to consistently reproduce the smoothing and calming effect it has on such recordings. I was using my MacBook Pro much more than PC for that reason but now I can throw the PC into the mix as it sounds almost as good.
I found no need to use the JitterBug with my MacBook Pro whatsoever.
