Just wanted to let everyone know that my problem is solved. Dusty spent quite a bit time with me on the phone finally getting to the root of the buzzing - a ground loop between my iMac and VPH-1.
You should know that Dusty was extremely patient working through the various potential solutions, hanging on the phone while I rebooted my Mac multiple times. What customer service and what a complete gentleman! I always enjoyed his products, but backed up with that kind of customer service makes them unbeatable. Even enjoyed a long chat about the state of the audio business!
Thanks again to Dusty and all those who took the time to help me out with my problem.
Craig