Fairchild 660

Tube-based audio compressor

The Fairchild 660 is a tube-based single-channel audio compressor invented by Rein Narma and manufactured by the Fairchild Recording Equipment Corporation beginning in 1959. The 660 was the first intelligent automatic volume control limiter. The Fairchild 670, introduced shortly after the 660, is a dual-channel version. The rarity of Fairchild compressors has made them highly desirable and very valuable, with a used 660 now selling for $20,000 or more and a 670 selling for $30,000–$40,000 or more. They are commonly referred to as the "holy grail" of outboard gear.

This keyword could refer to multiple things. Here are some suggestions: