Acronym for "bucket brigade device", an integrated circuit which implements a form of analog memory. A BBD divides an incoming signal into charge quantites (or "buckets"), which are passed down a line of capacitors, shifting to the next capacitor each time the BBD is triggered by a clock signal. Eventually the charge arrives at the end of the line of capacitors and is output from the device. As such, the BBD acts as a delay line. Speeding up or slowing down the clock has approximately the same effect as speeding up or slowing down a tape; it shortens or lengthens the delay time, and produces a pitch shift on whatever signal is moving through the BBD at the time. BBDs were widely used to implement relatively short delays used in flangers and chorus circuits in the 1970s and early '80s, until digital memory became cheap enough to supplant it. BBDs are not very accurate transfer devices; they have limited dynamic range and are noisy enough to require noise reduction in most applications; runaway can also be a problem. However, their characteristic distortion can also be a pleasing effect; the famous Roland chorus circuits of the early '80s were based on BBDs.

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