Point taken.
Furthur testing has been done, the original scenario was repeated (Tekkon 9v DIN-3 to Naiant and 5v USB to r-09hr), but this time, I ran line-in XLR to my pmd-661 which was running on internal AA's at the same time. I got the same noise on the devices. When the USB cable was removed from the equation, noise was gone.
Well, as far as this thread is concerned, maybe someone else can chime in who has had issues like this.