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Catch a Wave
You might have heard the term “sound waves.” It refers to the fact that sound travels in waves similar in some ways to the ones we see in the ocean: If you put a clean audio signal through an oscilloscope, you will see a line with smoothly rounded peaks and valleys. When an amplifier reaches a level at which it can no longer increase the output signal without altering the input signal, that is called distortion (it’s also known as clipping). On the ’scope, this distortion shows up as flattened peaks and valleys rather than the previously rounded peaks and valleys. This is true of instrument amplifiers as well as pedals, which use tiny amplifiers in their circuitry. Distorting a signal adds harmonic content or overtones that did not exist in the original. These overtones are actually present in everything from bird songs to flutes and cellos—yes, Virginia, there was distortion before rock ’n’ roll—and they add much of the character we love in so many guitar tones.
The amount that the waveform is squashed by this distortion goes a long way toward defining the difference between overdrive, distortion, and fuzz. A clean boost pedal’s job is to increase the output of your guitar signal only enough to give you extra volume or drive your amp to distort, without adding any grit of its own. An overdrive pedal adds some distortion to the signal but not a lot, while a distortion effect crushes the wave pretty heavily—and fuzz even more so.
In addition to adding extra harmonics to the signal, the squashing effect of distortion also compresses it, thus reducing the attack and dynamic range while adding sustain similar to what you’d get from an MXR Dyna Comp or another compressor pedal.
Now that we understand a bit about the technical differences of boost, overdrive, distortion, and fuzz, let’s take a look at how this plays out in the world of sound and tone.
Stacking the Deck
We’ve all heard the “plug-me-straight-in” philosophy from those who claim nothing beats the sound of a great guitar plugged into a great tube amp, without any pedals between them. Given the right instrument, the right stack or combo, the right player, and the right circumstances, it is hard to refute that theory: The tone produced by power tubes being pushed past their limit is hard to beat.
And though preamp distortion—the distortion that comes from the EQ circuit rather than from driving the amp’s power section beyond what it can output without distorting—has come a long way since the days of the silverface Master Volume-equipped Fender Twin, the sound sought by most adherents to the “plug-me-straight-in” philosophy is most definitely that of power tubes working hard. In the case of the earliest tube amps, the sound is attained by working them much harder than the designers originally intended. Crank up a Fender Deluxe, Vox AC30, Marshall plexi, or a boutique clone of a vintage amp, and the resulting distorted tone is a thing of beauty that’s highly responsive to pick attack and guitar-volume control. There is just one problem: These amps only achieve this sound within a limited range of volume. In other words, the amp has to be loud to get that sound.
If you only play in your basement or studio, with no complaining neighbors or family—problem solved. You can use an amp at its optimal volume to your heart’s content. When you play out in clubs, theaters, or even arenas, however, you will often find the sweet-spot volume to be either too loud, or in the case of smaller combos, not loud enough. If it’s too loud, you’ll probably be asked to turn down until all that lovely distortion turns into a clean “plink.” If it’s too soft, you might find yourself turning up until your gorgeous, open, singing sound is converted into a raspy, overly compressed mosquito buzz.
However, if you’re committed to this type of grit, there are solutions:
- Power attenuators like the Rivera RockCrusher (street $499, rivera.com, reviewed June 2011) and THD Hot Plate (street $328, thdelectronics.com) can be placed between your amp’s speaker output and speakers to lower the volume without having to turn down the amp. You will lose the part of the tone that is caused by the speaker breaking up, but it should get you pretty close to that “plug-me-straight-in” sound.
- Some players put a Plexiglas sheet in front of their speakers to reduce the stage volume. While this makes soundmen, bandmates, and the first couple of rows happy, it will seriously alter what you hear onstage.
- Some higher-powered amps (such as a Fender Twin Reverb) will still work properly if you pull half of their power tubes (two of the four, in the case of the Twin) to drive them harder and get cranked tones at lower volumes. Check with the manufacturer before you try this.
- Bring several amps of differing wattage to your gig. At soundcheck, determine which one enables you to get the tones you want without excessive volume.