Italo,
These double 2290 presets are for U2 covers. Sometimes Edge uses two delays; one delay is prominent in the mix, and the other delay is more subtle. I agree that most of the time the delays are probably in parallel, but some people think that serial delays may be used on some songs. I wouldn't mind being able to experiment between the two different types of sounds just to hear the differences for myself.
Cheers,
Jeff
