Well, with the test jig built and inserted into your 500 rack, LC53A module connected to the test jig, you will need to send a sine wave signal to the input of that 500 slot (XLR or whatever, depending on your rack). If you can monitor an unbalanced signal with your DAW, (set a channel up to record enable) I would just use the DAW instead of the DMM. If you use a DMM, you can just clip your probes on. If you need to make a cable for your DAW, you will need only 2 alligator clips. I think 'Chung has pics of that part in his build pics.