apperently he uses dual and triple rectifiers. the sound reminds me of some of petrucci's clean tones and he uses the dual rectifier.i dont hear any effects . maybe chorus.
According to Mesa, the rectifier came out in 1989...Petie said:Souls of Black was released in 1990 and the Rectifier didn't come out til 1991. Sounds pretty close to Metallica's tone on "Welcome Home (Sanitarium)" though, with the flanging and reverb. Could be a Mesa Boogie or a Roland Jazz Chorus, or it could be direct into the board with effects, or it could be a rented amp in the studio, ya never know.
Just digged out a back copy of Guitar World from 1990 and there is an interview with Eric and Alex, Eric used a Marshall JCM900 on the album (with Boogie tubes), whereas Alex used the ADA-mp1 into a Marshall JCM900 so he says.
The sound on The Legacy is a quite generic clean tone with chorus and some compression, the ADA can do this easily.