Official comment
I'm not 100% sure what you're asking... but I'll try and answer based on the two possibilities...
1) If you're trying to output audio from your iPhone to the DDJ-SR2, you would need to use an RCA-to-Minijack cable to connect the headphone output of the phone to one of the line inputs on the back of the SR2, making sure to toggle the input selector switch to LINE for that channel on the back of the unit, and the channel input selector to PHONO/LINE on the top of the deck.
2) If you're trying to use your phone as an input device, I'm sorry but the phone doesn't work that way; the output from the DDJ-SR2 is a line-level output, and if anything, your phone may accept a microphone-level input, but sending it line level would overpower the input and result in distortion, even if you had the right kind of cable.
