Using the second conjecture in the paper J. Guillera, “A New Method to Obtain Series for 1/π and 1/π2,” and inspired by the theory of modular functions, we find a method that allows us to obtain explicit formulas, involving eta or theta functions, for the parameters of a class of series for $1/ \pi$. As in J. Guillera, “A New Method to Obtain Series for 1/π and 1/π2,” the series considered in this paper include Ramanujan's series as well as those associated with the Domb numbers and Apéry numbers.