BC,
I think George hit the nail on the head. The cable you probably purchased is known locally as an In/Out cable, with a pair of 1/4-inch mono plugs that go into a 1/4-inch stereo plug. Its primary use is for sendng effects--not for combining signals. Wrong cable for what you hoped to accomplish. just a pair of ordinary instrument cables is all you need.
Good Luck,
Gary
------------------
Travlin' Easy
_________________________
PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)