Shure 520DX User Manual download pdf (Page 15)

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Sometimes this can be attributed to holes in the mic, but often the only solution is … don’t use

that mic!

Vocal mics and instrument mics are designed to be "directional" – to pick up more sound from

the front than from the sides or the rear, specifically to help avoid feedback on stage. So a well-

designed microphone can help with a feedback problem – but only when it is in free air – in

a rack or on a stand, and not in your hands. Once you pick up a microphone and cup it,

all bets are off. If you hand hold a mic, feedback will be more of an issue because the mic is

moving around and facing different directions. When you move your "cup" away from your

face, your other hand can act like a satellite dish and can catch and reflect more sound to the mic

than if it was in truly free air. Many players learn to manage this by pressing the face of the mic

against their chest while not playing. Ideally, you should be set up just a little further from "the

hairy edge" of feedback so it isn't too difficult to manage.

When you play acoustically, you can help to control feedback by ensuring that little to none of

your sound is coming through your monitors. Depending on the frequency of the feedback,

equalization (tone control) can help as well.

When you're playing amplified, all of the above applies. A microphone is designed specifically to

pick up sound waves from the air, so it is a much more sensitive and troublesome feedback device

than a guitar string. Consequently guitar amplifiers (and most harp amps start out as guitar

amps) are set up with much more gain than we need. This allows the guitar player to get

Hendrix-like feedback when he or she wants it, but it can be a nightmare for a harp player.

Gain is the most important variable in taming an amp’s tendency to feed back.

Remember, an amp is only so loud. No 5 watt, 8” speaker amp will cut through at a jam unless it

is mic’d. The best weapon of all is a more powerful amp with more speaker area. Read on for

more on this topic. But a typical guitar amp can be made much more harp friendly by reducing

its gain, so let’s talk about that for a moment.

Reducing#feedback#by#reducing#gain#N#amplifier#tube#substitution#

First, let’s define gain. Gain is not the same as volume. Gain is the slope of the line mapping input

volume to output volume. Here's an analogy. Imagine you have a light weight sports car with a

500HP V8 up front. Now imagine the gas pedal only moves 1/2". Idle is idle, full throttle is full

throttle - but the engine is so hard to manage in between, you have to drive even slower to be

safe. Now let's use the same engine but give the throttle pedal 5" of travel. Idle is still idle, full

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Shure 520DX User Manual Page 15