A dotted 1/8 note delay, short time ( about 125 ms +/- to taste) and limited repeats -adjust the feedback setting until you get the sound to kinda bounce to the beat. The Edge uses a lot of delay, bit of verb (try a spring), some dirt/distortion. But it's the "dotted 8th" with a specific type of timing. Here's a video showing how to dial it in. But the specific "Edge sound" is the dotted 8th with limited feedback (2 - 5 repeats), verb and a medium distortion. Here's a demo of it by someone.