I tried swapping out cables to differentiate sound. I need to proper rig to switch between the two cables quickly. I don't trust myself to recall how it sounded like after after the amount of time it took to swap them out. It's quite difficult to decern, and it makes you hyper attentive at looking for differences and if you recall the memory imprecisely, your impressions are not accurate. I have heard the argument that usb sounds harsher than optical or the usb sounds shrill or has glare compared to optically fed signal due to noisy line. How does that make sense, although at times, usb seemed brighter sounding than optical. Also, bit rate did change how I perceived sound as well.