I have an mbox2, and it only has one headphone output on it. This output is the only way to hear what's happening in protools through headphones. If i'm running a session, and my singer is in the other room recording with headphones, how would I go about listening to it at the same time? Could I get a two-channel mixer, plug the headphone output into it, and run two pairs of headphones out of that, or would that not work? A simple headphone splitter? what are my cheapest options.