Sorry Adam, you mixed up the types.
A DJ splitter is the one that sends left(resp. right) to one plug and duplicating the mono to become 'stereo' output so you get L+R output for each of the plugs.
As the app (or program) sends cue to left (right) and main to right (left) this is the one the use.
A stereo to mono splitter only splits to the 'tip' of the jack, so you don't get signal to the ring (or if ring is missing it is sleeve which may cause noise on one (worse case on both) of the output sides).
The 'normal' stereo splitter only splits stereo in identical L/R signal for the 2 plugs.
this is a solid DJ cable
https://www.amazon.com/Native-Instrumen ... tter+cableor one for your key ring
http://djworx.com/review-urbanears-slus ... nd-iphone/