The audio quality of LPs increased greatly over time, and a contingent of music fans maintain that the analog sound found on well-maintained LPs is superior to the finitely accurate digital sound used for CDs and MP3s. Early LP’s were monaural, but stereo LP’s became commercially available in 1957. In the 1970s, quadraphonic sound (four-channel) became available. These did not achieve the popularity of stereo, partly because of scarcity of consumer playback equipment, competing and incompatible quad standards (which played fine on regular two-channel stereo equipment) and partly because of the lack of quality in quad-remix releases. Quad never escaped the reputation of being a gimmick. Three-way and quadraphonic, which were favored and championed by artists like Leopold Stokowski and Glenn Gould, are only now making a small comeback with older masters being turned into multi-channel Super Audio CDs.
Besides the standard black composition, specialty productions are also produced on different colors of PVC (red, yellow, green, blue, white, clear, pink, multi-color and more) or special picture discs with a cardboard picture sandwiched between two clear sides. Several in different novelty shapes are also produced.
Although most LPs play at 33⅓ rpm, some super fidelity discs were designed to play at 45 rpm. There were also, early in the evolution of the LP, some releases (primarily spoken word) designed to play at 16⅔ rpm, and from the 1950s to the 1970s it was possible to purchase playback systems with four speeds: 16, 33, 45, and 78 rpm.
The composition of materials used has varied considerably over the years. Virgin material is preferred, but during the petrochemical crisis in the late 1970s, it became commonplace to use recycled materials, melted unsold compilations with all of the impurities. Sound quality suffered, with increased ticks, pops and other surface noises. Other experiments included reducing the thickness of LPs, leading to warping and increased susceptibility to damage. Using a bead of 130 grams of material had been the standard, but some labels experimented with as little as 90 grams per LP. Today, high fidelity runs follow the Japanese standard of 160, 180 or 200 grams.
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