Thanks so much, Erik. I think you've zeroed in on the issue. When I change the Macbook's output rate, the fizz gets adjusted (with some rates, it seems to go away; with other rates, the fizz is lessened; with other rates, the fizz is pretty loud).
The Parasound is supposed to have a very good DAC, or so I thought. Is the failure to lock just something that some DACs don't do, or do you think my Parasound's failure to lock indicates I just got a defective model? I have about a week before I'm outside the 30-day period with the seller (Audio Advisor). My big question now is whether, if I exchange my Parasound for a replacement of the exact same model, will the replacement be able to lock, or is this an inherent issue with the Parasound Halo Integrated. What do you think?