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A note about XLR audio. An XLR jack is a Balanced audio line. Comp is right that it is always mono. Unlike 1/4" or RCA, an XLR jack uses two wires for audio (+ and -) and a seperate "shield" for ground. This arrangement allows for longer cable runs without interference. (It’s much more technical than that, but that’s the gist). The PD-170 has an excellent audio interface to handle a Balanced line. Be sure of a couple of things. Set your phantom power switch (on the channel you connect to the camera to) to off (the +48V) as you may damage the sound board by returning voltage to an output. This is used to power condensor microphones (ie-the shotgun that came with your camera) only. Next set your input level on the camera channel to LINE. Every sound board is a bit different, but most good boards will provide you with a +4 level that should be well within your range to adjust. Good points on turning off the AGC in the camera and using the manual mode to set level. Also good idea to test in advance as you may need to adjust the level of the feed on the sound board output. Try to hook to a MONO or SUM out if the board has this. If not, either left or right will work fine, but be sure the mix is panned to mono or you will only get the channels panned to your output. Mackie boards are very popular but have some quirks as to channel routing, so be sure to test in advance.
The last thing to check is for what’s called a "ground loop". This is a hum or buzz that you cannot get rid of except by unplugging the feed or turning down the input in the camera. It is caused by interference on the grounding system. Without going into about 3 volumes of electrical theory, just watch for them and know they are very difficult to get rid of. Easiest solution is to run the camera on battery and avoid pluging the camera to anything other than the sound board that is plugged in to electric power.(this may or may not be an option, just an easy fix if you encounter the problem.) If you have this problem, check with someone knowledgable in sound systems and see if they can find you/make you an XLR cable with a ground "lift". This will usually knock out the source of the problem. (It’s just a circuit that disconnects one side of the ground to break the "loop".) You can also try Broadcast Supply Worldwide (www.bswusa.com) to see if they still have a "ground lift" adapter??
Hope this helps.
Best for the new year!