I've been getting a crackling on the headphone outs. I've been trying to use 1+2 as the master out and 3+4 as the headphone outs. Are there any latency settings I should be aware of that could induce the crackling?
Since the emi2|6's headphone output is shared with outputs 1+2, you need to use those as your monitor out, and 3+4 as your master out. As for the crackling, it's quite possible that your output is clipping, which live does not handle very well... try putting a compressor or limiter on your master insert.