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Audio Basics: Not As Simple As They Look? Identifying & Solving Microphone Problems
You never know everything and there’s something new to be learned every day
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Besides sound quality, there really isn’t much to think about when it comes to microphones, right?

Well, guess again!

Like all elements of a sound system, microphones present their own unique set of special problems.

Fortunately, a lot of these problems are relatively simple to solve. It’s just a matter of identification and appropriate action.

For example, most mic handles include a set-screw near the connector, with many models using this screw to ground the mic handle.

If the handle seems to be picking up hum when touched, check that the set-screw is fully secured down (turn clockwise until tight).

Inside the XLR connector on a mic cable is a ground lug, offering option of tying it to pin 1 or leaving it floating. If this ground lug is connected to pin 1, the connector shell is grounded.

Then, if the shell touches a grounded metal surface, a ground loop can occur, causing hum. So, a better approach is to float the shell.

Lighting cables and AC power cables radiate strong hum fields, which mic cables can pick up.

Keep mic cables well separated from lighting and power cables.

Keep a set of “tweakers” handy to tighten down that mic screw.

If the cables must cross, do so at right angles to reduce the coupling between them.

In addition, vertically separate the cables.

If your situation produces severe hum pickup when using dynamic mic models, try ones that include humbucking coils. (The Shure Beta 58 is probably the most popular example in this regard.)

Also, twisted-pair mic cable can reduce pickup of magnetically induced hum.

The more shield coverage, the less pickup of electrostatically induced hum.

Braided shield generally offers the best coverage; double-spiral wrapped is next best, and spiral-wrapped is worst.

Use twisted-pair cable to reduce pickup of magnetically induced hum.

And, routinely check mic cables to make sure the shielding is connected at both ends. For outdoor work, tape over cracks between connectors to keep out dust and rain.

Shocking But True
At times, electric-guitar players can receive an electric shock when they simultaneously touch their guitar and a microphone.

This is caused when the guitar amp is plugged into an electrical outlet on stage, and the mixing console (to which the mic is grounded) is plugged into a separate outlet across the room.

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