It's possible that the upsampling takes place as part of the A/D conversion process - as I said, that was just my understanding. I would suspect that the process that upsamples from 44.1/48kHz to 96kHz (or whatever higher sampling rate the 990 generates, I don't recall exactly what it upsamples to) is entirely within the digital domain, though, which is why I assumed the A/D step carried you up to 48kHz under normal circumstances and the upsampling process that is used for digital inputs is then applied identically for the analog signal.