  We study discrete Schroedinger operators with analytic potentials. In
particular, we are interested in the connection between the absolutely
continuous spectrum in the almost periodic case and the spectra in the periodic
case. We prove a weak form of a precise conjecture relating the two.
  We also bound the measure of the spectrum in the periodic case in terms of
the Lyapunov exponent in the almost periodic case.
  In the proofs, we use a partial generalization of Chambers' formula. As an
additional application of this generalization, we provide a new proof of
Herman's lower bound for the Lyapunov exponent.
