Is this a dumb idea? It appears that we've been doing this for ages and so far none of the musicians have complained. My understanding is that you'll just get an out of phase signal which sounds like it comes from each ear individually, not a phantom centre in the middle of your head. But does that bother people? Do people do this and not bat an eyelid?
Update: Signal goes from impedance balanced line level out from the desk to headphone amp, plugged in with a TRS. However input expects unbalanced stereo signal, not balanced. IEM's get plugged into the headphone amp.