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The world of music is full of gadgets and gizmos. They're magic boxes that can sound great if you know how to use them--but they can also sound awful if used improperly. Unfortunately, we bassists often don't get clued in about these things: what they are, how they work, and how they should be used.
To begin, let's talk about a few types of signal processors commonly used with bass. While it may seem as though there are hundreds of these gizmos to choose from, they're all really just variations on a dozen or so basic effects, which in turn fall into four categories: equalizers, dynamic processors, time-based effects, and synthesizing effects.
Equalizers. Audible sounds can be represented in terms of the frequency spectrum, a graph with the lowest-pitched sounds on the left and the highest-pitched sounds on the right. Since most sounds--the low E on your bass, for example--are actually a combination of many frequencies, a single note can stretch all the way across the spectrum. The proportions of these different frequencies determine a sound's timbre or tone; this is why an instrument that puts out more high frequencies sounds "brighter" than one playing the same pitch with fewer highs.
Equalizers ("EQs") alter the balance of the different frequencies, which helps to make instruments fit together in a musically pleasing way. For instance, if your amp is pumping out tons of lows but no mids, your bass will probably sound muddy and indistinct; in this case, a little low-cut and mid-boost EQ will make your notes "punchy" and more audible with better pitch definition.
There are several types of EQ. The simplest covers two frequency bands, with a bass boost/cut control and a treble boost/cut control. Add a midrange control, and you've got a 3-band EQ; 4-band and 5-band EQs (and beyond) provide more sonic flexibility. Sometimes the controls of an EQ are in the form of sliders; this is called a graphic EQ, because the physical positions of the sliders produce a graphic representation of the EQ's effect on the frequency spectrum. An even more flexible type of equalizer is the parametric EQ; it uses three knobs per band, allowing you to specify the center frequency of each band, the amount of boost or cut, and the bandwidth or "Q," which determines how narrow or wide an area of the frequency spectrum you're affecting. The semiparametric EQ, commonly found on amps, is simply a parametric EQ without bandwidth controls.
EQ is a complicated matter, and an entire series of columns could be written on EQ alone. For a more in-depth look at how to use EQ, check out Sound Solutions: An Introduction To EQ in July/Aug '92.
Dynamic processors. These devices affect the dynamics (the loudness and softness) of a signal. The simplest is the volume pedal, which is basically a volume knob you control with your foot. A more complex circuit is the compressor, which reduces the dynamic range of your signal by making the softest notes louder and the loudest notes softer. Compressors smooth out the signal and can make your bass more punchy and consistent-sounding from note to note. They also protect speakers from being dangerously overdriven, although this job is often left to a limiter, a type of compressor that limits your signal from getting any hotter past a certain point. The other type of dynamic processor is the expander or noise gate. By making the softest sounds even quieter, an expander can lower the "noise floor" of your signal by reducing the levels when you aren't playing.
Even though compressors and expanders are technically opposites, they're often used simultaneously--with great results. The compressor evens out your notes, and the expander cleans up everything in between. Single-unit compressor/expanders are commonplace in recording studios and complex rack systems.
Time-based effects. These circuits split your signal in half, electronically delay one of the lines, and then recombine the signals; the amount of delay determines the type of effect. Delays longer than about 75 milliseconds create "echo" or "slap-back" effects. Shorter delays (10-20ms) produce chorusing effects, making you sound like two or more bassists playing together. Delays shorter than 10ms create flanging and phasing effects in which certain frequencies cancel out, changing the tone. Choruses, flangers, and phasers always have a "modulation" function, which causes the delayed half of your signal to speed up and slow down; this imparts an animated quality and can produce "whooshing" or "liquidy" effects, depending on how the modulation parameters (usually labeled "rate" and "depth") are set. A delay unit with a broad range of delay times can produce any of these effects, but many bassists prefer boxes dedicated to specific effects, such as chorus and flanging pedals.
Synthesizing effects. The most common of these is the octave divider; it analyzes your signal and synthesizes notes one octave below. Most effective when you're playing high on the neck, octavers allow you to explore the upper range of your instrument without losing the low end. They sound especially good with fretless; Pino Palladino often uses an octave divider, with great results.
Distortion units count as synthesizing effects because they give your signal high frequencies that weren't there before. A drop of distortion makes your sound ruder and rawer, although some distortion units work much better with bass than others. As with any type of equipment, you need to try several units and choose the one that works best for you.
One last note: The key to smart signal processing is using effects
judiciously. Your playing--not the effect itself--should be what the listener
hears; the effect should act merely as a spice or accent. Even though an effect
may sound cool, it can also sound gimmicky and distracting--and it may cause
listeners to think you really don't have anything to say musically. Listen to
the way the masters employ effects, and then do the same--use them with
taste.
Karl Coryat is BASS PLAYER's Senior Editor.