I spoke to PS Audio this afternoon. They are basically just using the same B&O ICE modules that are available from many other manufacturers of digital amps. However, there is an innovation that the volume is controlled directly by controlling the gain of the amplifier itself, eliminating the need for a pre-amp.
But this is very similar to having a CD player with a digital volume control and connecting it directly to the amplifier.
But this is very similar to having a CD player with a digital volume control and connecting it directly to the amplifier.