Ed_sawyer...Thanks for the info. Dropping the LSB is how you multiply by 1/2, in context of my comment. For further gain reduction I suppose they do more shifts (dropping more bits). Perhaps they figure that as the volume level goes down you don't need 16 bits, 15 bits, 14 bits, etc. as the LSB is not audible anyway. However, I would not design it that way.
One idea that someone could use to mitigate the evils of digital gain control would be to add a very simple (cheap) 4 or 5 step analog attenuatior between the digitally controlled source and the power amp. This would be used like a "range" switch, to select the approximate volume desired, and then the digital control could be used to make only fine adjustment. The analog range selector would, for one thing, take care of the attenuation that is always necessary simply to cut the preamp signal down to match the power amp sensitivity. (Preamp designers always put out more volts than necessary to be sure that their product will work with any power amp). Of course, this "range selection" approach would also be suitable for automatic digital control.