If you run balanced lines, either mic level or line level, you are undoubtedly using 3-pin XLR connectors. They are much sturdier than 1/4″ connectors and provide a better electrical connection. However, there is one thing you need to be aware of when wiring your system, and that is which pin you are going to use as the ‘hot’ connector.
Pin 1 is ALWAYS ground. It never changes, and never will change. The other two pins are a little different. In the “old days,” (late 70s), the “standard” was Pin 1-ground, Pin 2-neutral, Pin 3-hot. It makes logical sense if you think that if pin 1 is ground, the pin numerically furthest was Pin 3, so that was hot. The pin in the middle, 2, was “neutral.” Most US and British-made equipment adhered to this standard. Then came the Japanese products spearheaded by Yamaha, and they all used pin 2 as hot, and pin 3 as neutral.
Everybody has gradually shifted to the “Japanese standard” and now pin 2 is hot with pin 3 being the neutral.
It should be noted that due to the physical layout of the XLR connector, it doesn’t make ANY difference at all, since all of the pins are equally spaced in a triangle shape. You just have to make sure when connecting pieces of gear together that they all use the same pin as hot, or you can run into trouble.
One of those problems is if you have a piece of gear that has Pin 3 hot, and you are feeding something that has Pin 2 as hot, the signal will be 180 degrees out of phase. This, in itself, may or may not cause any problems, but I am a firm believer that a positive signal voltage swing at a mic preamp should result in a positive voltage swing the rest of the way through the system, and should result in an outward movement of the speaker cones, and therefore result in a positive pressure wave being generated. It can make an audible difference on some instruments. Kick is a good example. The drummer’s beater hits the drum head, and the initial percussive impulse moves the head toward the listener. If the speaker cones move toward the listener, the drum sounds good, and percussive. If the initial impulse moves the cone back, away from the listener, it results in something that doesn’t sound nearly as percussive, since the initial result is to decrease the pressure of the air.
There are also times where you may need to tie neutral and ground together when connecting two pieces of gear together. If piece A has Pin 3 hot, while piece B has Pin 2 hot, and you are using a standard XLR-XLR connector, you will have trouble, since you will be shorting hot to ground, and connecting neutral to the ‘hot’ conductor of piece B.
Now, you could go through the entire system, checking every piece of gear for which pin is hot, and make adapter cables that swap pins 2 and 3 at one end (and ONLY one end), but then you have the problem of “special cables,” which I hate. If you are troubleshooting a problem, you constantly have to be aware of which cables need to be “special cables, and what exactly those “special cables do” while you are substituting. You can’t just grab any old cable and use it. Since having to troubleshoot a system as complex as a sound system is not trivial, and rarely happens during a lull in activity or under ideal conditions, this is one thing you really don’t want to have to worry about.
It would be MUCH better to go through the entire system, and rewire EVERY XLR connector on every piece of gear so that they all have the same pin hot. You can pick whichever one you want. As I said earlier, there is no electrical or structural advantage to either one. Personally, I would pick whichever one your console uses. Since it has the highest XLR jack/inch density. it would definitely be the biggest hassle to switch. While you are at it, it can be worthwhile to go through all of your mic cables and check them as well. You run into the occasional one that has been repaired at some point, and someone got Pin 2 and 3 switched on the end they fixed.
In fact, I would recommend that once a year, you go through EVERY cable you own, cut the ends off about 6-12″ back, and completely remake every cable. Nearly every cable failure I have ever seen has been at a cable end from repeated flexing or stresses on the solder joints. Just cut off the cable nearest the ends where it has suffered the majority of the flexing and twisting, clean out the solder cups in the connectors and flow new solder in them, strip and tin the conductors, and put them all back together. This would be a good time to add shrink-tube strain reliefs, if you don’t already use them. This will improve the reliability of your cables greatly, and may just save you the joys of crawling behind amp racks, in the dark, 10 minutes before showtime, with a Big Name Star breathing down your neck, trying to find out which cable has finally failed because it was bent, pulled, and twisted one time too many. It is just this kind of situation which can ruin your reputation as a professional-grade sound company, and can result in the loss of future jobs. In the market you have chosen, and in an economy such as we now have had thrust on us, you need every advantage you can get, and absolutely must avoid things like this.
Every situation is a learning situation. In this situation, you would learn that a couple of hours of tedious work each year can prevent 5 of the worst minutes of your life.