| That's the easiest way, but 99% of the time that output signal will be way too hot. Remember you are taking that output from a small amplifier (which drove the speaker). If you follow the wires back from the speaker, you'll usually find they lead to a single transistor, which is the entire amplifier. Connecting to the input of that xtr will usually give you a signal that is at a better level to work with. Of the three legs of that xtr, one is "ground", shared by both input and output. It's often the middle leg, but not always. Of the other two legs, one is input and the other is output. connect wires to the input leg and the ground leg, and run those to your new jack- ground goes to the sleeve. If you aren't sure how to test which leg of the xtr is input and which is output, wire it up with alligator clips first; if it doesn't work, switch the connections to the legs. | 
