XLR Wiring Tips
Advice on this important cable connector.
The reduction in price of XLR connectors over recent years makes this professional audio connector a worthwhile proposition for home studios. No one would doubt the mechanical advantages of a connector which won't split if you tread on it, won't part company with the cable if you trip over it and which won't melt into a blob of plastic and metal when you solder it.
It is worth considering a wholesale changeover to XLRs, especially if you take equipment on the road. Purchasing XLRs in bulk will reduce the cost still further and it is possible to buy male and female line plugs for well under a pound a time if you buy enough.
Generally there is only one standard in use for connecting 3 pin XLRs, but beware as some equipment of American parentage sometimes uses variations to the wiring, and some European equipment reverses the sex of plugs. The only standard worth remembering, and sticking to is this:
Signals come out of a Male XLR.
Signals go into a Female XLR.
If you can't remember your sexes, the males have little protrusions or pins that stick out. The females have holes to stick them into!
XLRs are designed for 'balanced' wiring, but it doesn't preclude the use of 'unbalanced' systems, and by observing some basic rules the two can be completely compatible. The worst part about converting your studio set-up to XLRs is the recording equipment, which may offer only ¼" jacks, phonos or even, if you are unlucky, DIN connectors. You will need to make up a load of conversion leads with an XLR at one end and an oddball connector at the other. This is cheaper than buying chassis-mounting XLRs and you don't have to hack great holes in the equipment.
Conversion from unbalanced to balanced wiring takes place in the converter leads, and from that point on, all other leads will be balanced XLR. All your connecting leads can then be standard: female XLR to male XLR with whatever length of lead you wish. To make up longer leads just join up shorter ones. No more searching in the suitcase for the odd lead which has a reverse wired DIN one end and 3-5mm stereo jack socket the other!
Wiring your collection of standard XLR to XLR leads should utilise balanced microphone cable, ie. two conductors plus overall screen. Several types of cable are available, all much of a muchness. Some types use braided wire for the screen, other types use foil with a drain wire for soldering, whilst the other type uses a conductive plastic sheath for screening, again with a drain wire to connect.
Most microphone cable is available in a rainbow of colours which is great for identifying cables, or even better for colour-coding lengths into standard runs. The only reservations are that some types of cable twist more easily than others and become knotted; other types, particularly plastic sheathed, go very hard in cold weather, which is not a deal of fun for open air winter gigs, or if you leave the cables in a cold van overnight.
The wiring standard for balanced XLRs should be:
Pin 1. Earth, screen or drain wire.
Pin 2. Hot, or the wire with the most predominant colour.
Pin 3. Cold, or the other wire of the two conductors.
All XLRs are numbered and pin identification is easy. The chassis of the XLR is not connected to pin 1 but a tag is usually available to solder to the chassis of the plug. However, it is not essential to wire to this - it can cause more problems than it cures if the chassis of the XLR rests on the central heating system at a gig, resulting in hum loops.
Make sure that the outer insulation of the cable goes well into the body of the XLR so that the cable grip can bite onto something worthwhile, then screw the grip up tight.
A useful aid to wiring XLRs, or any plug for that matter, is to make yourself a small box containing the mating connectors of all the plugs you solder up. Weight this box down with plasticine and use it to hold your plug whilst soldering - it is easier than using a grip or vice and less likely to squash the plug.
The conversion leads from equipment sockets to XLRs is where you adopt any change from unbalanced leads (one wire plus screen) to balanced leads (two wires plus screen).
Unbalanced connections to the XLR are:
Pin 1. Earth, screen or drain wire
Pin 2. Signal wire, or Hot.
Pin 3. Earth, screen or drain wire (ie. shorted to Pin 1).
Balanced ¼" inch jack connections convert as follows:
Pin 1. Chassis or sleeve of jack.
Pin 2. Tip of the jack.
Pin 3. Ring of the jack.
After conversion, the only long leads you need to carry are XLR to XLRs - even for loudspeakers. Some loudspeakers have XLR connectors but most use ¼" jacks, and I have lost count of the number of times they have failed to work because of poor or shorted ¼" jack connections. I therefore adopt a special standard for loudspeakers as follows:
Pin 1. Earth, screen or common.
Signal, live or Hot.
This odd connection has two advantages. The first maximises the use of standard microphone cable for connecting speakers via XLRs, the second is for safety. With lots of unidentified XLRs floating about, the last thing you want is some wally plugging a loudspeaker lead with 200 watts of signal on it, up the backside of a microphone!
With this wiring configuration, as pins 2 and 3 are wired together, there is no signal between them, so your precious microphone will not be blasted away. If the mic is unbalanced, the worst you can do is blow the output fuse of the power amp.
If you thought XLRs were only for the professionals, think again. Although the cost of converting your studio may seem quite high initially, you will be buying a system which will last for years, and which is the standard used by everyone else. This ultimately saves on the number of different leads you need to connect up, whilst being ready for you when you update your equipment to professional, balanced operation.
And finally, if you have wondered why they are called XLRs, the answer is an abbreviation - EXtra Low Resistance connector. It was originally developed for use in test laboratories for connecting sensors to equipment and the like, because the scientists were sick to death of their experiments being ruined by poor connections - just like you and me!
Feature by Quentin Howard
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