UC (noise reduction)

The UC compander system (with "UC" derived from Universal Compatible or Universal Compander) is a noise reduction system for vinyl records, aiming at highest playback compatibility even without corresponding UC expander.

Overview

The UC compander system was developed in the 1980s by VEB Zentrum Wissenschaft und Technik (ZWT) of VEB Kombinat Rundfunk und Fernsehen (RFT) in the former German Democratic Republic (GDR). The system was based on the observation that the dynamic range of typical audio source material almost always needs to be reduced in the vinyl mastering process and that very similar system parameters are commonly applied in the process either by the sound engineer or through the hardware. The idea was to develop a compander system loosely emulating this process and to formally standardize on its characteristics. By emulating the typical characteristics of this compression, UC compressed records would not produce acoustical artifacts which would not have been present in similar form on the produced disk anyway, and that thereby they would remain virtually unrecognizable, so that consumption would remain acoustically pleasing and compatible even if records were later played back without UC expander. Initial experiments with a compression factor of 2:1:2 were found to still cause too many artifacts to maintain this compatibility, which led the UC developers to implement a broadband compander utilizing an adaptive compression factor between 1.33:1:1.33 (or 1.67:1:1.67) (at 0 dB) and 1:1 (at −20 dB). In contrast to earlier vinyl disk noise reduction systems such as dbx disc, High-Com II or CX 20, the system deliberately limited the reduced disk noise by about 10 to 12 dB(A) only, an amount similar to what could be achieved by other compander systems where only the receiving side of the medium was exposed to users and therefore the system had to remain playback compatible with a large installed base of devices without corresponding decoder (such as Dolby FM or High Com FM in radio broadcasting).

In fact, the results were found so good that, especially for records produced with Direct Metal Mastering (DMM) (but not exclusively), the system was undocumentedly introduced into the market by the East-German VEB Deutsche Schallplatten through record labels such as Amiga, Eterna and Nova since 1983/1984, with UC-encoded records only identifiable by a shy extra "U" engraving in the disk's silent inner groove area. Up to 1990, over 500 UC-encoded titles were produced.

The economical necessities in the former GDR, however, made it impossible to introduce a suitable UC decoder at the same time.