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UD-4, also known as UMX or BMX, was a discrete 4-channel quadraphonic sound system developed by Nippon/Columbia (Denon).

UD-4
UD-4 format logo.png
Media type Vinyl record
Encoding Analog signal
Capacity Four stereo channels
Read mechanism phono cartridge
Developed by Nippon/Columbia (Denon)
Usage Audio storage

Only 35 to 40 items are encoded in this format, and it was marketed only in the UK, Europe and Japan.

The UMX standard contains two subsystems, BMX, a basic 4-2-4 matrix decoder (different from QS Regular Matrix), and QMX, a 4-4-4 system.

UD-4 is the process of modulating QMX onto a record with a process similar to CD-4, but also matrix encoded.

The system suffered from incompatibility with regular stereo playback due to phase differences between the left and right channels.[1]

A BMX decoder could be used to play back UD-4 recordings, but, by adding a special cartridge and a UD-4 demodulator, two supplementary channels could be extracted and used to enhance directional resolution.

UD-4 systems first encoded the four original channels into four new channels. Two of these new channels contained the original four channels, matrix encoded. The other two contained only band-limited localization information, and were encoded with carriers similar to the CD-4 system.

UD-4 was less critical in its set-up than CD-4, because the carriers did not have to carry frequencies as high as those found in the CD-4 system.[2]


ReferencesEdit

  1. ^ Cooper, Duane. "THE UD-4 SYSTEM". HI-FI NEWS & RECORD REVIEW - MARCH 1975. Retrieved 5 February 2012. 
  2. ^ Cooper, Duane H.; Shiga, Takeo (June 1972). "Discrete-Matrix Multichannel Stereo". Journal of the Audio Engineering Society. AES. 20 (5): 346–360.