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Noise Gates 101: What They Do & How To Use Them To Their Fullest
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You should note that none of the gate’s controls affect the audio directly – they affect the control voltage to the VCA, which affects the audio level. A gate has no affect on the tonality of the audio.

Note that the frequency controls come before the detector. Therefore, they affect what the detector responds to. Also, side-chain inserts come before the detector.

The detector is probably the most important part of the gate circuitry. A poor choice of detector can make a gate built around the world’s best VCA chip a piece of junk!

A noise gate is really a special case of a device called a downward expander. (Aside: an expander affects signals both above and below a threshold; a downward expander only affects signals below a threshold.

That’s an important distinction.) Instead of having a range control, an expander has a ratio control.

Ratios are expressed as in : out, where in is the input level in dB, and out is the output level in dB. Ratios range from 1:1 (meaning no expansion) to 1:10 and higher (lots of expansion).

When the signal is below threshold on an expander, it is attenuated by an amount determined by the ratio control.

So, for example, if you set your downward expander ratio to 1:4, that means that for every 1 dB below threshold, the VCA will attenuate the signal by 4 dB.

A signal at –4 dB, then, would be attenuated by 16 dB. A gate is nothing more than a downward expander with a very high ratio, in much the same way that a limiter is a compressor with a very high ratio.

Finally, regarding gate usage: Gates are a double-edged sword, and they can be immensely frustrating devices if the drummer is either very uneven with his playing, or if he’s got an excellent sense of dynamics.

Too much gating and the good drummer’s quieter parts get clipped off (unless you’re riding them, which you have to do). Not enough gating, and the lousy tone of the bad drummer rings forever.

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