UD-4
UD-4 was a discrete four-channel quadraphonic sound system for phonograph records introduced by Nippon Columbia (Denon) in 1974. This system had some similarities with the more successful CD-4 process introduced by JVC and RCA in 1972.
 | |
| Media type | Phonograph record |
|---|---|
| Encoding | Analog signal |
| Capacity | Four audio channels |
| Read mechanism | phono cartridge |
| Developed by | Nippon/Columbia (Denon) |
| Usage | Audio storage |
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 standard used for UD-4 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.
A BMX decoder could be used to play back UD-4 recordings, but, by adding a special phono cartridge and a specialized 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 high frequency carrier signals similar to the CD-4 system.
The system suffered from incompatibility with regular stereo playback due to phase differences between the left and right channels.[1]
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.[2]
References
- Cooper, Duane. "THE UD-4 SYSTEM". HI-FI NEWS & RECORD REVIEW - MARCH 1975. Retrieved 5 February 2012.
- Cooper, Duane H.; Shiga, Takeo (June 1972). "Discrete-Matrix Multichannel Stereo" (PDF). Journal of the Audio Engineering Society. AES. 20 (5): 346–360. Retrieved September 28, 2018.