UD-4 was a discrete four-channel

quadraphonic sound Quadraphonic (or quadrophonic and sometimes quadrasonic) sound – equivalent to what is now called 4.0 surround sound – uses four audio channels in which speakers are positioned at the four corners of a listening space. The system allows for th ...

system for

phonograph records A phonograph record (also known as a gramophone record, especially in British English), or simply a record, is an analog sound storage medium in the form of a flat disc with an inscribed, modulated spiral groove. The groove usually starts near ...

introduced by

Nippon Columbia , often pronounced ''Korombia'', operating internationally as , is a Japanese record label founded in 1910 as Nipponophone Co., Ltd. It affiliated itself with the Columbia Graphophone Company of the United Kingdom and adopted the standard UK ...

(

Denon is a Japanese electronics company started in 1910 by Frederick Whitney Horn, an American entrepreneur. Denon produced the first cylinder audio media in Japan and players to play them. Decades later, Denon was involved in the early stages of de ...

) in 1974. This system had some similarities with the more successful CD-4 process introduced by

JVC JVC (short for Japan Victor Company) is a Japanese brand owned by JVCKenwood corporation. Founded in 1927 as the Victor Talking Machine Company of Japan and later as , the company is best known for introducing Japan's first televisions and for ...

and

RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Com ...

in 1972. Only about 35 to 40 LP album titles were encoded in this format, and it was marketed only in the UK, Europe and Japan. Most of these releases were marketed by the Denon label. The UMX (universal matrix) standard used for UD-4 contains two subsystems: *BMX (quadrasonic, two channel matrix), a basic 4-2-4

matrix decoder Matrix decoding is an audio technology where a small number of discrete audio channels (e.g., 2) are decoded into a larger number of channels on play back (e.g., 5). The channels are generally, but not always, arranged for transmission or recordin ...

(different from

QS Regular Matrix Quadraphonic Sound (originally called Quadphonic Synthesizer, and later referred to as RM or Regular Matrix) was a matrix 4-channel quadraphonic sound system for phonograph records. The system was based on technology created by Peter Scheiber, but ...

); *QMX (four channel matrix), a discrete 4-4-4 system (adding band-limited localization information encoded with high frequency carrier signals similar to the CD-4 system). The UD-4 process modulated both BMX and QMX into a single record. This way, a BMX decoder could be used to decode quadraphonic sound using an existing stereo record player, while by using a special phono cartridge and a specialized UD-4

demodulator Demodulation is extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated ...

discrete supplementary QMX channels could be extracted (enhancing directional resolution). In theory this allowed backward compatibility with existing players and records, but the system suffered from incompatibility with regular stereo playback due to phase differences between the left and right channels. Phono cartridge set-up for UD-4 playback was less critical than in CD-4, because the high frequency carrier signals were not as high as those found in the CD-4 system.

References

{{Quadraphonic sound Surround sound Quadraphonic sound