Perhaps this is old news to everyone, but I found this nice presentation that explains why it is very difficult for digital volume control to match the performance of analog volume control:
http://www.esstech.com/PDF/digital-vs-analog-volume-control.pdfThe main takeaway is that unless the digital volume control system has access to the internal data path of the DAC, it cannot match the signal to noise performance of analog volume control. Even then, the DAC has to be 32-bit internally and the signal has to be 16-bit. However, if digital volume control is implemented correctly (at least under these parameters), the analog volume control has to be "exquisitely" well designed to beat the digital one.
