Digital delay pedals tend to give the user much more control and stability than their solid state analogue cousins. However, their sound can differ greatly - analogue delay lines are generally reputed to have a much warmer, smoother sound. They typically use a series of large capacitors which buffer the audio signal in order to create the actual delay, and which also tends to make them substantially more expensive to manufacture. Other than sound quality, the other key difference is the manner in which they behave when the delay time is altered in real time. A digital delay line takes a sample or snapshot of the incoming audio signal and then delays it accordingly, whereas an analogue unit physically stores the audio in capacitors or chips. When the user manipulates the delay time in real time, an analogue unit will change the sound in a very different way, sometimes creating extremely unusual pitch changing effects reminiscent of 60s sci-fi movies - this is one of the reasons that musicians and producers often seek out these units. Some digital devices now actually model this effect!