Digital-to-analog converter

A digital-to-analog converter for a pulse code modulated (PCM) signal having a plurality of code groups and a given sampling rate comprising:

• a source of said PCM signal;
• first means coupled to the output of said source for increasing said given sampling rate of said PCM signal;
• second means coupled to the output of said first means for selecting a predetermined number of the most significant bits of each of said code groups of said increased sampling rate PCM signal;
• and
• third means coupled to the output of said second means for converting said most significant bits into a pulse stream having a mean density which is proportional to an analog signal represented by said plurality of code groups wherein
• said first means includes fourth means coupled to the output of said source for interpolating additional pulse code groups in the intervals between said plurality of code groups;
• and
• wherein said fourth means includes fifth means coupled to the output of said source for storing each of said plurality of code groups until the next of said plurality of code groups is received, said fifth means also being coupled to the input and output of said second means to generate an error signal when said error is determined;
• and
• wherein said fourth means is coupled to at least the output of said second means to determine any error resulting from said selection of said predetermined number of most significant bits;
• sixth means coupled to said fifth means for circulating each of said stored code groups two or more times while stored;
• said
• sixth means also being coupled to the output of said fifth means and to the input of said second means to couple said error signal to the input of said second means to reduce said error.