Originally Posted by Ross Ridge
Interference from a nearby FM station wouldn't cause a recognizable sound to be heard on the headphones. It requires relatively complex circuitry to demodulate an FM radio signal, and that circuitry only exists inside the receiver's AM/FM tuner module. If it is an FM radio station he's hearing then it's likely crosstalk from the the tuner module like DavidMP suggested. Removing the FM antenna or tuning to non-existent station like he recommended should fix the problem.
On the other hand all it takes to demodulate an AM signal is a single diode, so a strong nearby AM radio station can easily cause recognizable interference in all sorts of electronic devices. I used to be able to hear a nearby AM radio station when I put my ear next to my speakers even when my old (tuner-less) integrated amplifier was turned off.
Originally Posted by DavidMP
Right. I meant disconnecting the antenna so that no FM reception can be made even if not on the tuner input.
Well guys I have good news, turns out its not FM I am hearing on other inputs that are silent, which explains why I never heard any commercial breaks or DJs
Comically the sound leak I can hear is Pandora! I was listening to Pandora and switched to HDMI, cranked up the headphone volume and could hear the same music.
FYI, it was not Pandora on Zone2/3, experiment was on MAIN. The sound leak ceased when I went back into Pandora and hit "stop."
A weird quirk nonetheless of such an advanced system, but I love my Yammy.