the present invention involves apparatus and techniques for converting analog data , preferably audio signals , to digital information , which digital information is preferably recorded from two separate main channels onto main tracks and includes a third or backup track for recording thereon partial or most significant portions of that information recorded on the main tracks . the invention involves apparatus and techniques of each data group on each main track and the backup track ; checking for synchronization codes arranged between data groups ; and checking for a match of that appropriate portion of the main track data against the data on the backup track , with , when potentially erroneous or questionable data is detected , the invention providing for comparison of main and backup track data groupings for determining which is most likely correct or , in the case where neither data grouping is identifiable as most likely correct , the invention provides for substitution of last correct data or integration between good data . the preferred invention incorporates clocking at the signal input for data stablization , and first - in - first - out circuitry at the output for reducing the effects of wow and flutter to produce a very high quality conversion of digital to analog form to pass to a speaker system .