33CD

33CD, also known as 33 1/3 RPM, refers to a standard for compact discs (CDs) that specifies the rotational speed of the disc to be 33 1/3 revolutions per minute (RPM). This standard was established by the Compact Disc Digital Audio (CDDA) specification, which was developed by Philips and Sony in the early 1980s. The 33 1/3 RPM speed was chosen to ensure compatibility with existing vinyl records, which typically spin at this speed. This rotational speed allows for a playing time of approximately 74 minutes for a standard CD, which is sufficient for most audio recordings. The term "33CD" is often used to distinguish this standard from other types of CDs, such as CD-ROMs or CD-Rs, which may use different rotational speeds. Despite the advent of digital music formats and streaming services, the 33CD remains a widely used standard for audio CDs.