6/17/2023 0 Comments 33 rpm 7 inchIn any doubt, the speed is usually written on the central label. Due to its limited manufacturing run the SX2 has become a sought after rarity among pro DJs. As a general rule, 12 vinyl are 33 RPM and 7 are 45 RPM. A raised barrier was also added to contain the head in the event of miscuing and a polished surface inside the barrier to minimize damage to the stylus. One of the main design revisions, required was a series of 'ribs' on the underside of the platter to prevent warping from the extreme changes in temperature during the manufacturing process. The SX2 (Single Extender, Rev 2) was manufactured by plastic injection at Spirit, Inc. He would then do the final assembly (bonding a lathe cut acrylic center and a foam pad) and packaging by hand. The original design (The Extender) was made up of a platter die-cut from sheets of plastic that McLaughlan would drive on the hood of his car from the supplier in Cambridge, MA to the die-cutter in Ipswich, MA. By 1949 magnetic tape was used for mastering. Original LP release: ML 4001 Session producer: Goddard Lieberson Originally Released 1945 Mono recording, Bruno Walter Edition, SMK 64459 ML4001 was mastered direct-to-disc on 16-inch lacquer. McLaughlan, a Boston area nightclub DJ, came up with the design to make 7" discs easier to handle when mixing. Original 78 rpm release: set M-577 (mx XCO 34739 - XCO 34708). Not necessarily more than one song per side, but definitely 33 RPM and with 'regular' spindle holes. The SX2 and The Extender were designed and manufactured by Mark McLaughlan between the early 1980s and early 1990s. They're 7-inch, two-song singles, one song per side, but they're stereo and they play at 33 rpm and have a small spindle hole like an LP. Several manufacturers made "spider" adapters in slightly varying shapes and many different colors, though yellow and red were most frequently used. The Hutchison adapter included small bumps called "drive pins," which locked the adapters together while revolving, thus preventing the stacked records from slipping against each other. Commissioned by RCA president David Sarnoff and invented by Thomas Hutchison, spiders were prevalent in the 1960s and sold tens of millions per year. The former RCA Corporation introduced a snap-in plastic insert known as a spider to make 45 rpm records compatible with the smaller spindle size of a 33 + 1⁄ 3 rpm LP record player. The EMI version is circular, with four small notches holding the center part onto the rest of the record. Some EMI and other British records have a similar feature. These had a triangular section molded in with an LP-size spindle hole that could be punched out for playing on 45 rpm spindles. Capitol Records for a time produced what they called "Optional Center" or "O.C. A differently shaped, but similarly difficult-to-use metal adapter was made by Fidelitone. They were made of solid zinc, difficult to insert into a record and almost impossible to remove without breaking the disc. The first 45 rpm inserts were introduced by the Webster-Chicago Corporation, also known as Webcor.
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