A delay line which uses an analog technique of delaying the signal. Currently, all available analog delays use a circuit known as a "bucket brigade". This circuit uses an analog sampling technique: a capacitor captures the instantaneous voltage value of the signal being delayed. Then, on a clock signal, the voltage is passed to the next capacitor in the chain, and the first one captures a new voltage. Delay time available depends on the number of capacitor "buckets" in the chain. The delay time is varied by varying the clock rate, which effects the bandwidth available.
A large number of analog delay devices were available from about 1970 (when the techniques for manufacturing bucket-brigade integrated circuits were developed) through 1990. This was because digital memory was expensive at the time. However, bucket-brigade analog delays are relatively noisy circuits, with some processing artifacts (such as the loss of bandwidth as the delay time is increased). Once digital memory became less expensive in the 1990s, digital delays supplanted analog delays for most purposes. Nonetheless, analog delays continue to be used in some flanger and reverb circuits, and some performers prefer them for low-fi effects.