I absolutely agree with this. I guess my only point (and it's not even your problem of course) is if someone (for example only) connects Qutest to an earthed USB source and earthed preamp then the USB galvanic isolation of Qutest will essentially be defeated as both sides of USB interface are connected to earth, no? But as mentioned, this is not your problem to worry about. You are dead right (of course!) when you say "My job is to make the quality of the source (with bit perfect data of course) become irrelevant". How we integrate your gear is out of your control.