  We construct functorially a class of algebras using the formalism of double
derivations. These algebras extend to higher dimensions Crawley-Boevey and
Holland's construction of deformed preprojective algebras and encompass
symplectic reflection algebras associated to wreath products. We use this
construction to show that the quotient field of a symplectic reflection algebra
is "rational", confirming a pair of conjectures of Etingof and Ginzburg.
