Assuming that "A/D" is meant to be "D/A," the 106 dB must be some DAC chip spec, not actual system.
I think "A/D" is correct; in the quote you gave, it's in the context of "using analog sources," which typically are digitized for processing.
And a question . . . after resetting to factory status, did you install any available firmware upgrades from Anthem? I don't know if they exist, and I don't know if they might have improved this badly performing unit. I do know that Anthem makes updates available, that they might affect performance, and that they might need to be installed through its ARC software.