UD-4

UD-4^[1][2] was a discrete four-channel quadraphonic sound system for phonograph records introduced by Nippon Columbia^[3] (Denon) in 1974. This system had some similarities with the more successful CD-4 process introduced by JVC and RCA in 1972.

UD-4

Media type	Phonograph record
Encoding	Analog signal
Capacity	Four audio channels
Read mechanism	phono cartridge
Developed by	Nippon/Columbia (Denon)
Usage	Audio storage
Released	1974

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)^[4] standard used for UD-4 contains two subsystems:

• BMX (quadrasonic, two channel matrix),^[5][6][7] a basic 4-2-4 matrix decoder (different from QS Regular Matrix);
• QMX (four channel matrix),^[6] a discrete 4-4-4 system (adding band-limited localization information encoded with high frequency carrier signals^[1] similar to the CD-4 system).^[8][4]

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 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.^[9]

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.^[4]

References

1. Hope, Adrian (April 10, 1975). "Two more innovations for the hi-fi addict". New Scientist. p. 81.
2. Cooper; Takagi (March 1975). "THE UD-4 SYSTEM". Hi-Fi News & Record Review.
3. Myers, Alfred (May 1978). "FCC's 4-Channel Listening Tests" (PDF). Audio: 24.
4. Cooper, Duane H.; Shiga, Takeo (June 1972). "Discrete-Matrix Multichannel Stereo" (PDF). Journal of the Audio Engineering Society. 20 (5). AES: 346–360. Retrieved September 28, 2018.
5. US4152542A, Cooper, Duane P., "Multichannel matrix logic and encoding systems", issued 1979-05-01 
6. Gerzon, Michael (December 1974). "Surround-sound psychoacoustics" (PDF). Wireless World: 483.
7. Eargle, John M. (December 6, 2012). Handbook of Recording Engineering. Springer Science & Business Media. ISBN 9789401093668 – via Google Books.
8. Robinson, Larry. "Quadraphonic Systems". MidiMagic. Retrieved 2023-01-12.
9. Cooper, Duane; Takagi, Toshihiko (March 1975). "THE UD-4 SYSTEM". Hi-Fi News & Record Review.