the answer:
this is a mail that Peter Rizzo, the author of "Deconstructing the Edge" sent me:
- Shimmer to me is a type of phase shifting sound
(like you hear with a MXR Pahse 90 pedal or other
phasers, even a UNivibe can give you a similar sound
on more extreme settings.) But with Edge is little
more complex. The sound was made famous by Dave
Gilmour and SRV who used Rotating Leslie Speaker units
to creat this big spacious sound. Its little trick as
while he sends shimmer treatment to one amp, and the
DI, he often runs ther treatments to his other amp, so
the mixture can often be confusing to identify. The
Leslie speaker give the wow/flutter sound of the
speaker being spun around. A lot of guys on the group
get it wrong and ont understand it. You can here it
best on the MTV interveiw when Edge is playing I Still
Havent Found What I am looking for...awesome (but its
mxed with a little delya which gives it a more spatial
sound)