#compact cassettes

Companies wanted the attention of consumers and digital music could be made much crisper and free of the quality issues from the wear and tear of analog formats.  The problem with the digital cassette tape compared to the analog cassette, however, was that digital audio requires a lot more tape. This meant that unlike the Compact Disc, the digital audio on the DCC had to be compressed.

The music at the time was recorded by sampling it as much as forty-eight thousands times per seconds.  Data is stored in binary and in this case, each of the samples is represented by a number written in a 16-digit string of binary (0's and 1's).  With a stereo, two channels means two signals so storing a single second of music requires 1.5 million 1's and 0's.

Put it all together with additional memory requires for control and error calculation and a single second of music requires 2.8 million 0's and 1's - or about 2.8 megabits.  At the time of the product launch, we were still sticking floppy discs in our computers and even the most powerful floppy discs used in personal computers at the time could only hold about 4 seconds worth of digital music.

In order to get all of that data packed into a digital cassette tape, developers realized that it would have to move extremely slowly.  If the digital cassette tape moved at a standard speed it would need to be extremely long.   Using technology from video cassette recorders, Phillips was able to create a DCC that would move tape slowly however read quickly while carrying a large amount of data.

At the time, Phillips was well respected for their ability to stay on top of advanced technology and create quality products.  With the benefit of their development teams, they were able to use data compression to reduce the binary needed to store the digital music.  This allowed them to use linear tracks and reduce the overall amount of tape

A Complicated Technology

Even with compression though, cramming all of that data into linear tracks is far from easy.  A standard analog tape has only four tracks - two stereo channels on each side of the cassette tape.  The Phillips DCC, using tape of the same width as standard analog cassettes, had 18 tracks with 9 going in one direction and 9 going in reverse.  Eight of those tracks would contain the music while the 9th track was all control information.

Because of this, a sophisticated recording head was developed in order to read all 9 tracks in parallel.  This sped up the flow of information onto and off of the digital compact cassette.  It's also why the machine was backwards compatible; the sophisticated head could easily play simple analog cassette tapes.  With the sophistication of the digital compact cassette however it's easy to see why a standard cassette player couldn't read the digital tape.

A Question of Quality