Actually while the data levels are digital the timing can be considered analogue The higher the speed the larger the jitter Some CD players can reclock the signal some apparently dont Without a fully reclocked data sream jitter may get through to the DAC and beyond where it will be audible This was a quality issue in Audio CD production when the mastering machines in the factories were sped to x speed It was a Pink Floyd CD where an unexpected drop in quality was first found and it was finally tracked down to the speed increase at the manufacturing of the master discs The problem was addressed by Sony and as an employee of a CD fab told me solved by improving the mastering machines to yield perfect results at the higher speeds