  We study the relationship between two key concepts in the theory of
(di)graphs: the quotient digraph, and the lift $\Gamma^{\alpha}$ of a base
(voltage) digraph. These techniques contract or expand a given digraph in order
to study its characteristics, or obtain more involved structures. This study is
carried out by introducing a quotient-like matrix, with complex polynomial
entries, which fully represents $\Gamma^{\alpha}$. In particular, such a matrix
gives the quotient matrix of a regular partition of $\Gamma^{\alpha}$, and when
the involved group is Abelian, it completely determines the spectrum of
$\Gamma^{\alpha}$. As some examples of our techniques, we study some basic
properties of the Alegre digraph. In addition we completely characterize the
spectrum of a new family of digraphs, which contains the generalized Petersen
graphs, and that of the Hoffman-Singleton graph.
