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Our local village church has a decades old, minimal PA system which essentially consists of a microphone running a cable to an amp at the back.

They have a normal looking microphone plugged into an XLR cable but when I plugged in my SM58 for better vocal, it didn't work - no sound at all.

Is there a likely, obvious reason why? Are there multiple standard ways a microphone would work, or has this changed in the last 20 years?

  • Have you tried plugging you mic and lead into the p.a. directly? With 3 pins, there are several ways it may have been connected, especially if done by an amateur. Worth making up a link lead with old wiring to new, just to work in the church. Pretty straightforward. – Tim Mar 6 '18 at 15:40
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Are there different standards for XLR cabling?

Yes. The XLR connectors has been used for a lot of different things. They were invented around 1950. In audio today it is mostly standardized, but vintage equipment may use the XLR connector in various ways. It was quite commonly used for connecting loudspeakers to power amplifiers.

Today it is almost exclusively balanced mic or line level audio. Pin 2 and 3 carry the balanced signal, ground on pin 1 is only connected to shield and does not carry any signal. [Edit: pin 1 has an important role when you use phantom powered mics, but that is a different question]

The church might have one of these: the Shure 545 could be wired for unbalanced connection. It is quite possible that the amplifier experts a high impedance mic with signal between pin 3 hot and pin 1 ground. If you connect a modern SM58, low impedance, balanced signal on pin 2 and pin 3, you will not get any sound.

If you want to use your modern mic, you will most probably need a Line Matching transformer, some examples shown here. I must be clear on that I am not sure exactly which one to use.

It would help if you could describe the make and model of amplifier, maybe even a picture.

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If the cable is simply acting as an XLR extention cable - female wall box or plug at one end, male at the other, it's reasonable to expect standard wiring, pin 1 to 1 through the shield, 2 to 2, 3 to 3. But, particularly in a church, you have to accept the possibility of it having been installed by someone well-meaning but ignorant of standards. You also need to look at what's at the other end of the cable, and how it's connected.

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The answer is yes, my old church has a public address system from the sixties and it requires female xlr connectors on each end of the cables. Also different microphone manufacturers wired their products out of phase from other manufacturers. However, neither of these conditions would result in no sound. I recommend testing your mike, then your cable, then the input to find where the fault may be. Also, many of the old systems had plug in transformers for the mic inputs, perhaps that may have been removed.

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