How to get more than one output channel
To get the most out of mixHDJ you need to be able to monitor one deck whilst outputting the other deck live. There are a few ways to achieve this by means of splitting the left and right output from a single channel.
      Make your own cable. Left channel from jack to socket for headphones, and right channel from jack to socket for mixer/amp.
* Notice how left and right channels are combined back at the stereo socket.
Using off the shelf products, 3.5mm to 2xRCA, and 2x single RCA socket to 2 x RCA to make mono output onto both L&R channel on headphone and mixer.

split left and right channels
RCA cableRCA splitter combine
Dont confuse this with the widely available headphone splitter lead. It looks the same but does not split left and right channels.

If you want to use off the shelf products you can use the following
combination of connectors to replicate the custom made cable.

1 x  This plugs into the phone

1 x    This Cable goes to your amplifier

1 x

1 x    To plug the headphones into