UD-4 was a discrete four-channel

quadraphonic sound Quadraphonic (or quadrophonic, also called quadrasonic or by the neologism quadio formed by analogy with "stereo"">portmanteau.html" ;"title="/nowiki>portmanteau">formed by analogy with "stereo" sound – equivalent to what is now called 4.0 s ...

system for

phonograph records A phonograph record (also known as a gramophone record, especially in British English) or a vinyl record (for later varieties only) is an analog sound storage medium in the form of a flat disc with an inscribed, modulated spiral groove. The g ...

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 C ...

(

Denon is a Japanese electronics company dealing with audio equipment. The Denon brand came from a merger of Denki Onkyo (not to be confused with the other Onkyo) and others in 1939. It originally started as Nippon Chikuonki Shoukai in 1910 by Freder ...

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

RCA RCA Corporation was a major American electronics company, which was founded in 1919 as the Radio Corporation of America. It was initially a patent pool, patent trust owned by General Electric (GE), Westinghouse Electric Corporation, Westinghou ...

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 incorrectly referred to as RM or Regular Matrix) was a phase amplitude Matrix decoder, matrix 4-channel quadraphonic sound system for phonograph records. The system was based ...

); *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 the process of 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 ...

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