XLR and TRS Wiring Chart

The standards. Pin 2 hot has been the professional convention since AES14 settled it, and every current console, microphone and processor follows it.

Four recipes cover nearly every adapter a church has ever needed to make or specify. Each one is written as the connection at both ends, so it can be handed to whoever is soldering.

Symptom back to cause. Almost every fault here is found in under a minute with a cable tester, which is why a tester belongs in the rack drawer of every church.

Polarity is not phase, although everybody calls it that. Polarity is a straight inversion: the positive half of the waveform becomes the negative half. One microphone wired backwards among many produces no obvious fault on its own channel, because a single inverted signal sounds identical in isolation.

The damage appears when two microphones pick up the same source. Two overhead microphones on a choir, a snare with a top and bottom microphone, or a pulpit covered by a gooseneck and a lapel: if one path is inverted, the shared content cancels. The result is a choir that sounds thin and distant, or a snare that loses its body, and the volunteer chases it with equalisation for months because nothing is obviously broken.

This is also why polarity test cables must be marked unmistakably. A red-shelled, labelled reversal cable is a useful diagnostic tool. An unmarked one in the general cable bin is a fault generator that will eventually be plugged into the choir microphones on a Sunday and produce a problem nobody can reproduce on the Monday.

The same logic applies to loudspeakers. Two boxes covering the same seats with one wired backwards cancel through the crossover region, which is heard as a hollow, weak sound in the middle of the room and blamed on the room. Check polarity at the amplifier terminals when a system is commissioned, and again whenever a cable has been replaced.

Wireless bodypack connectors are manufacturer specific. A TA4F on a Shure transmitter, an equivalent connector on a Sennheiser and one on an Audio-Technica carry bias voltage and audio on different contacts. A headset such as the Shure SM35 Performance Headset Condenser Microphone - TQG is sold terminated for a particular system, and rewiring one to another brand is a job for the microphone manufacturer’s adapter rather than a soldering iron and a guess.

Console insert wiring is not universal. Tip send and ring return is the common US convention and several European consoles reverse it. Read the manual for your desk before making an insert cable, because a reversed insert produces a channel that appears to work and is actually routing the return back out.

Ground lifting has limits. Lifting pin 1 at one end of an audio cable is a legitimate technique for breaking a ground loop on a signal line. Lifting a mains safety ground is not, ever, under any circumstance. If the hum needs the chassis grounds separated, the correct device is an isolation transformer on the audio.

Digital connections are not diagnosable this way. A Cat5e run carrying Dante or AES50 either works or does not, and a marginal one produces silence or dropouts rather than the graduated symptoms in the fault table. Test digital runs with a network tester and replace rather than repair.

It says nothing about phantom power. Several of the symptoms above change behaviour when 48 volts is applied, and the interaction between phantom and a faulty cable can destroy a ribbon microphone. That is the phantom power requirements chart.