The present invention relates to method and apparatus of converting a series of data words into modulated signals. This method generates for each data word a number of intermediate sequences by combining mutually different digital words with that data word, scrambles these intermediate sequences, translates each scrambled sequence into a (d,k) constrained sequence, detects running digital sum (RDS) every bit for each translated (d,k) constrained sequence while counting sign changes of each RDS, selects one sequence of which RDS changes most in sign among the (d,k) constrained sequences after discarding every sequence of which maximum value of RDS is beyond a preset threshold, and records the selected sequence onto a recordable medium such as an optical disk or a magneto-optical disk. The present invention can suppress DC component more remarkably in case that a sequence becomes longer.