CX (noise reduction)
Noise reduction system for recorded analog audio
CX is a noise reduction system for recorded analog audio. It was developed by CBS Laboratories (a division of CBS) in the late 1970s as a low-cost competitor to other noise reduction (NR) systems such as dbx disc and High-Com II, and was officially introduced in 1981. The name CX was derived from "Compatible eXpansion", a feature of the technique.
CX is a companding system: the dynamic range of the signal is reduced before being written to the medium, then recovered (expanded) afterwards. Such a combination reduces the effect of noise on the resulting signal and expands the dynamic range that can be practically used. Directly playing the recording without the corresponding expander still results in an acceptable sound, hence the claim of being compatible.
Use on vinyl LP records
CX was originally designed by CBS as a noise-reduction technology for vinyl LP records, similar to the earlier dbx disc (based on dbx II) and High-Com II systems, but, like the later UC system, it aimed at the lower-cost consumer mass market rather than high-end audiophile niche markets only. CX-encoded records required a special CX expander connected to a stereo system, in order to fully reproduce the CX encoded sound on the LP. However, in contrast to dbx disc and High-Com II, CX-encoded records, like UC-encoded records, could also be played without a decoder with a resulting (claimed acceptable) amount of dynamic range compression. CX being a 2:1:2 compander system, a noise reduction of 20 dB(A) was achieved for a resulting maximum dynamic range of typically 80 to 85 dB(A) (other sources claiming up to 95 dB(A) or even 107 dB). The theory of operation is described in U.S. patent 4,376,916.
“CX (noise reduction)” enters the record as noise reduction system for recorded analog audio. Crown Archives preserves that source wording while asking what noise, reduction and Noise can confirm, complicate or overturn.
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