Waynes quite right, but I suspect where 'Chicago' became confused was the rather silly way that Behringer describes 1/4" TRS phone plugs as
stereo 1/4" TRS inputs. This mislabelling is derived from the multiple use of the TRS connector on stereo headphones, where in fact the tip is one channel and the sleeve is the other channel. It simply does not apply here.
From the 1500 manual in part:
1500.jpg
brucek