33 RPM - 33 RPM
33 RPM ( 33 revolutions per minute or 33⅓ revolutions per minute ) is an acronym for recordings on vinyl records . It is used as a designation for a sound recording format widely used today in vinyl publications.
It is the speed most used when recording vinyl records for fidelity. Generally on 12 " , 7" ( singles ) records, although 10 "gramophone records were also used for some time (no longer in use). RCA Victor first started using this new speed in 1931 , with the idea that in a disc the longer recording time. [ 1 ] Vinyl records recorded at 33 RPM are also well known for being called LP ( Long Play , long duration) this name is for the difference between the duration of a disc of 78 RPM versus a 33 RPM one.
The first 33 RPM records came out right around the time of the Great Depression of 1929 . Just coinciding with this great crisis, they were not successful, since the new format implied buying new equipment. [ 2 ]
By comparison, the microgroove on a 33 RPM record was as fine as a human hair, spanning about 118 grooves per centimeter , whereas the 78 RPM record only had 33 grooves per centimeter. In comparison: one 33 RPM drive equals five 78 RPM drives, the new drives were also lighter. In addition, in a 2.4 meter long shelf of 78 RPM records, now with the new format, only half a meter is enough to store the same amount. [ 3 ]
At first this format was used for recording on 12 "diameter discs, but later it was also used for recording 7" singles at this speed. This speed is still used today, in fact it is the most used, although record companies make 45 RPM releases on 10 "discs.
Although most LPs were recorded at 33 RPM, due to the high fidelity some continued to be recorded at 45 RPM , especially the singles. Some recordings (mainly the vocals), were equalized to record at 16 RPM and try to avoid the "spike noise", but without success. From the 1950s to the 1970s it was possible to buy turntables with all four speeds: 16, 33, 45 and 78 RPM .