dbx is a company who is most known for their history of building dynamics processors. In fact they developed the modern VCA that made high quality dynamics processing possible. But their name has also been somewhat synonymous with noise reduction. Like Dolby, the term dbx is often used generically to mean noise reduction. Dbx noise reduction systems work in a way that is fundamentally different from the early Dolby systems. They use compression (to tape) and expansion (from tape) of the audio to lower the relative noise levels and effectively double the dynamic range. The systems work well, but like Dolby, have side effects that some users find unacceptable for modern high quality recording. The development of these systems has slowed in recent years and they have pretty much fallen out of favor with professional recording engineers. There are two main types (type 1 and type 2) that we will discuss in the next few days.