4.2. LP and EP records Vinyl 'LP's were one of the most popular consumer formats for music reproduction from their inception in the late 1940s until compact disk started to gain significant commercial market share. They are still in use and playback equipment is still readily available. The main drawbacks with records are the accumulation of dust and susceptibility to scratching and warping. In 1948, Columbia introduced the 'micro-groove' LP (long-playing) record: a 12 inch 'vinylite' disk with a speed of 33 1/3 rpm. The purpose of this format was to be able to reproduce a large proportion of the Classical music repertoire, with disks having 2 sides which would play for 23 minutes each. In 1949, as a response to Columbia, RCA Victor introduced the 7-inch 'micro-groove' EP (extended play) record, playing at 45 rpm and again made from vinylite. This format was mainly suitable for popular songs, and it became the mainstay of the pop music industry. The popularity of the new formats led to the fall of the 78 rpm gramophone record. The first stereo records were introduced in 1958. Earlier mono records will play back adequately on stereo equipment. Modern record turntables have direct electrical output, which can be used directly for digitisation without the need for microphones, although a turntable pre-amplifier will be required (see section 5.7). It is important to use a good quality turntable for digitisation, and also to place it so that it is isolated from contact with any source of mechanical vibration. Record styli and cartridges tend to act like contact microphones - a turntable stood on a table which itself is on a wooden floor, for example, will tend to pick up footsteps, doors banging and so on. 4.3. Open reel tape Open reel tape consists of magnetic-coated tape wound onto a plastic or metal spool or reel. Magnetic tape recording technology developed during the 1930s and 40s with the German magnetophon, and became commercially available in the early 1950s. Due to its quality and flexibility it displaced the lateral disk (record) as the most widely used sound recording medium in the music and broadcast industries, up until the rapid expansion of digital audio technology in the 1980s and 90s. There are several formats, defined in terms of the physical width of the tape in inches. They are ¼-inch, ½, 1, and 2-inch, and different formats are used for different applications. The narrower formats are usually used for recording in mono or stereo; in stereo recording, the recording machine would record on two bands or 'tracks' along the length of the tape, one track taking sound for the left hand speaker and one for the right. The wider formats are used for multitrack recording, where the tape is divided into 4, 8, or 16 or more tracks, allowing many sounds to be recorded onto the same tape simultaneously whilst the volume of each remains independently controllable. Open-reel tape machines are available from professional audio suppliers. They have signal outputs, so they can be connected to other audio equipment and computers. Whilst stereo connection to a computer is fairly simple, these machines do have a complex technical setup procedure requiring specialist skills. If the tape is in a multitrack format, either each track needs to be digitised separately (which would require multi-channel audio hardware for the computer), or a mix needs to be made which would require the use of a suitable mixing console and would be best undertaken in a recording studio. 4.3.1. Noise reduction With any analogue audio tape, there is always background hiss evident on playback. Various methods have been used to overcome this, involving electronic circuitry to process the sound as it is recorded onto the tape (a process called encoding), and then again as it is played back (called decoding). If noise reduction was used in recording the sound, it must be used to play it back. Also, it is crucial to use the same kind of noise reduction. If an encoded tape is played back without appropriate decoding, then the hiss may be much louder than if no noise reduction had been used at all, and the sound may be distorted in other ways too. The most widely used types of noise reduction are those developed and marketed by Dolby Laboratories (Dolby A and Dolby SR are their proprietary NR methods for professional use, whilst Dolby B, C and S are those designed for domestic cassette machines). Another fairly common noise reduction system is dbx. Open-reel tape machines usually require separate noise reduction units to be connected: they are not built into the machines. Noise reduction units are also available from professional audio suppliers.
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