An annular Helmholtz damper for a gas turbine can combustor is provided, the annular Helmholtz damper having an axis and comprising: an inner wall and an outer wall concentrically arranged with respect to the axis to define an annular damping volume arranged around a can combustor; a front and a rear circumferential plate for closing upstream and downstream the annular damping volume; at least oneintermediate circumferential plate arranged between the front and the rear plates for dividing the annular damping volume in a main and a secondary volume; at least one main neck passing at the innerwall and configured for fluidly connecting the main volume with the can combustor chamber; at least one intermediate neck passing the intermediate circumferential plate configured for fluidly connecting the main volume with the secondary volume; a plurality of purge holes passing the rear circumferential plate configured for entering purge air in the secondary volume; a plurality of intermediatedrain holes passing the intermediate circumferential plate configured for draining collected liquid from the main volume to the secondary volume.