At a certain point, you’ll start to hear the sound of the idling guitar amp coming through—that’s the gate opening up slightly. When the ratio control is all the way down, the amp noise should be exactly as loud as if the expander weren’t in the signal chain at all; in other words, the gate is all the way open.

When you record a track, look for a happy medium between these points. When the signal chain is idling, the gate should be closed enough to quiet the track signifi cantly, but not closed so much that passages with no playing sound unnaturally silent next to played passages (unless, of course, that’s the effect you’re going for).

You also shouldn’t be able to hear the gate noticeably opening or closing when you start or stop playing. As much as possible, it should simply sound like your system is a lot quieter.

The trick to using an expander effectively is to find suitable threshold and ratio settings based on the sound you’re about to record, as well as the song you’re recording.

You want the expander to be responsive to any sound you make during the performance—in other words, to anything that you actually want recorded on your track—but not necessarily anything else.

Play lightly and let some notes or chords decay. Think about the performance you’re about to record: Will you be playing full-out through the whole track? Is there a point where you’ll need to hold a chord for several seconds? Will you be playing any passages very quietly?

Test out any such critical performance moments and listen to how the expander reacts. If the expander seems to be too sensitive to what you’re doing, turn up the threshold control a little.

Adjust the controls one at a time until the expander is doing its job cleaning up your signal chain, without calling attention to itself. You may need to compromise—one pair of settings may be good for one part of the song while another is good for a different passage.

Try to find settings that work as well as possible across the whole performance. If necessary, you can always punch in certain sections that require very different expander settings.

Attack & Decay: Most (if not all) expanders have these controls. You’ll recognize these terms if you have experience programming synthesizers: attack specifies how fast something rises, and decay specifies how fast it falls afterward.

In the case of an expander, attack determines how fast the gate opens when its threshold is suddenly exceeded, and decay determines how fast it closes again when the signal suddenly goes away. You can usually set these knobs and forget them.

Normally you want a very quick attack (so as not to cut off the beginnings of sounds) and a medium decay—perhaps around 200 milliseconds—to make sure the ends of sounds don’t get truncated.

The two sections of an integrated compressor/expander unit may have only one set of attack and decay controls but separate ratio and threshold; that’s okay. Having the same settings for both sides usually works fine.

Indicator LED: This is a handy visual element that you can use in conjunction with your ears. One LED, or a series of LEDs indicating a range of levels, may light to show that the device is actively expanding the noise downward.

When the gate begins opening, the LED may go dark, or a series of LEDs may progressively turn off as the gate opens wider. Indicator LEDs aren’t really that necessary on the expander side—they’re much more useful in compression—but they’re nice to have anyway.

Next time out, I’ll talk about the opposite end of the dynamic range spectrum: compression.

Editor’s Note: This article is excerpted from Karl Coryat’s Guerrilla Home Recording - 2nd Edition. To acquire this book, click over to the ProSoundWeb Book Store. NOTE: ProSoundWeb readers receive free shipping when entering promotional code PSW at checkout. (offer valid to U.S. residents, applies only to media mail shipping, additional charges may apply for expedited mailing services).

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