Cable Repair

Do you have a corner where all the broken microphone cables are thrown? Are you confused about how to fix those cables? Then this column was written for you!

No matter how well a cable is made, it will eventually break given enough time and use. Let's look at the three most common microphone connectors and learn how to fix them.

Figure 1
2 Conductor 1/4" Phone Plug

Figure 2
Unbalanced Cable

First, the two-conductor 1/4" phone plug (Fig. 1). This connector is usually found with high impedance unbalanced microphones. The cable has a single inner-conductor (wire) which is surrounded by tiny wires woven into a braid (Fig. 2). The wire braid is called the cable shield. It helps keep interference out of the microphone signal. Connect the inner-conductor to the tip connection of the phone plug (Fig. 3). The shield is soldered to the sleeve connection. When you're finished, crimp the cable clamp onto the cable. This will provide good strain relief.

Figure 3

Figure 4
3 Conductor 1/4" Phone Plug

Second, the three conductor 1/4" phone plug. It is also called a TRS (Tip, Ring, Sleeve) or stereo 1/4" phone plug (Fig. 4). This is used for balanced microphones or equipment. The positive wire (often the lighter color) is soldered to the tip connection (Fig. 5). The negative wire is connected to the ring connection. As before, the shield is soldered to the sleeve connection.

Figure 5

Figure 6
3 Pin “ XLR” Connectors

Third, the most reliable microphone connector is the three pin type (Fig. 6). It is often called an "XLR," which is actually a brand name. The male plug has three pins. The mating female connector has sockets. This connector is the standard professional microphone connector. Fig. 7 shows how a two conductor shielded cable is connected according to national and international (IEC) standards. However, not every manufacturer follows the IEC standard. Please consult your specification sheets for your equipment. You should be sure every microphone you own has its positive wire on the same pin number.

Figure 7

Everybody agrees on which wire connects to Pin 1. The shield connects here. Some cable companies also connect a wire from Pin 1 to the connector shell ground lug. We would not recommend doing this, because this can cause a ground loop to occur. Ground loops can cause a hum or buzz.

How Pins 2 and 3 are wired is not critically important, but it is important that both ends of the cable are wired the same. For example, the red wire on Pin 2 of the male plug would connect to Pin 2 on the female plug. It is wise to establish a wiring convention for your school. For instance, make the light color wire the positive wire, and connect it to Pin 2. The dark color is the negative wire, and it is tied to Pin 3. Connecting audio equipment can become very complex. There are unbalanced and balanced inputs and outputs. Then throw in transformers or direct coupled inputs or outputs. Now add impedance to the equation. Confused? Please give us a call if you need help. We can answer your questions!

by Ron Huisinga © 1996 Internet Sound Institute (www.soundinstitute.com). This article is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com

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