When you say "the headphones work fine on other sources" do you mean different pieces of equipment (like an iPod) or do you mean that the Denon provides the headphones with sound on AM/FM but not on Blu-Ray (or something)?

Is it possible that the Denon requires an analog input for the headphone jack and that the source component you are trying to listen to is only connected to HDMI or SPDIF?

bibere usque ad hilaritatem