Our recent tips on wiring polarity have generated a few more general questions about how to change the polarity of wire connecting gear. This week we will discuss a few permutations of how to wire cables for various circumstances. Other permutations can be covered in the future as needed. (Before you go on make sure you understand and follow the information from the 12/23/99 TTOTD as it contains the background that makes the following information more relevant.)
It's important to first understand how cables are normally wired. Here is what we say is the "normal" way to wire an XLR cable:
| Female End | Male End |
| Pin 1 – Shield................... | Pin 1 – Shield |
| Pin 2 – Hot (positive).......... | Pin 2 – Hot (positive) |
| Pin 3 – Cold (negative)........ | Pin 3 – Cold (negative) |
The distinctions of positive and negative don't really exist in a cable. The thing(s) a cable connects to is what makes one lead or another a positive. However, for the sake of clarity the above diagram is labeled with the positive and negative distinctions as they "normally" occur in audio connections.
The main instance where this wiring can lead to trouble is if you have a piece of gear in a chain that is wired backwards from the rest (pin 3 hot instead of pin 2). Be clear here. If you connect two devices that are pin 3 hot you do NOT need to modify a cable in order for them to work properly.
If you do need to reverse polarity on a cable you can do it at either the male or female end. It makes no functional difference. But don't do it at both ends. Doing it at both ends effectively returns the cable to normal operation. An example of reversing the polarity of an XLR cable to accommodate a Pin 3 Hot device would be as follows:
| Normal (Pin 2 Hot) device | Abnormal (Pin 3 Hot) device |
| Pin 1 – Shield................... | Pin 1 – Shield |
| Pin 2 – Hot (positive).......... | Pin 3 – Hot (positive) |
| Pin 3 – Cold (negative)........ | Pin 2 – Cold (negative) |
Notice that Pin 2 of one end is connected to Pin 3 of the other end and vice versa. This is how you reverse the polarity of an audio signal in a balanced cable. Tomorrow's TTOTD will feature XLR to TRS connections.
