hi sir,
he used the direct line (2) of this amp modded by jose' (wow)arredondo.I've got a marshall arredondo mod.It is really unbelievable amazing.It or he, 'cause is live he eats and sleeps like me,he's got 2 line level output,so Mr vai goes in his rack and goes out into two
power amp or more.He used also Shiller soldano amps in this way and i pray someone to tell me the settings of theese shiller amps.
He maybe isn't got the power tubes or he put a load in the speaker jacks to not crash the output trasformer.
In a normal amp you must go out from send and go in your effect rack.You must have a line mixer in the rack to put in stereo the ambience effects(delay/reverb or so)go out with 2 lines into a power amp and into 2 4x12 cabs.You must put away your power tubes on the head or you built a load resistence (4ohm) and put it in the speaker jack.Set your ohm in your head on 4ohm.
That's all.
After FIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIRRRRRRRRRRRRRRRRR RRREEEEEEEEEEEEEEEEE!
I54U
Alessandro