DJ Cable takes advantage of algoriddim‘s djay app’s Split Output mode, which will send the master output to the left channel and the cue output to the right channel. With any other app, DJ cable will output the audio’s left channel through the jack labeled with the speaker icon, and the right channel out through the jack labeled with the headphone icon.
You might have your wires crossed: Make sure that you have your headphones plugged into the jack labeled with the headphones icon, and that your PA is plugged into the jack labeled with the speaker icon.
Make sure that you have Split Output mode turned on in the djay app’s settings. If Split Output mode is not turned on, you’ll hear the master output through both sides of the splitter.
algoriddim’s djay app compiles the main output into one mono channel, and the cue output into a second mono channel. This means that both jacks on the DJ Cable will output mono audio.