I have a nice little Greco headphone amp made in the 90s (I think). It works fairly well, *BUT* even with the guitar *not* plugged in, I get a subtle white noise in the background through the headphones.
It's runs on two AA batteries so it's not plugged into the wall.
Sound does come through when I plug the guitar in and the aux in works fine, too, and if I play a little loud I almost can't here it but the moment I stop playing I hear it and it drives me nuts.
How can I troubleshoot this thing? Do you see anything in the pics?