I got this used recently. However, There is a button selector for TUNER but there is no way to hook up an antenna. Compared to photos of otherStage Ones, the place where the coax connector should be is not there, not even a knock out. What gives? When I press the TUNER button, numeric station are there, but obviously there is no sound. Secondly, there are TUNER RCA inputs on the back to the right of AUX RCA inputs. Weird, huh? Thanks for your help.