miércoles, 1 de mayo de 2013

Efectos de Distorsion para No - Ingenieros

Distortion has been with rock n’ roll from its earliest days. Just listen to the fuzzy tones on Ike Turner’s “Rocket 88” and Goree Carter’s “Rock Awhile,” the first ever rock n’ roll songs. The sound was accidentally discovered after players recorded with faulty, damaged, or just plain cheap amplifiers. Before long, many players were trying to get the sound by purposely damaging their equipment—Link Wray is arguably the most famous for this, having punched holes in his amp’s speaker with a pencil he found lying around the studio.

Today, you can hear distortion in any type of music—from hip hop beats to commercial jingles—and fortunately, you no longer need to destroy your equipment to get that sound. In the early ’60s, the first distortion pedals hit the scene, allowing players to get really gnarly sounds by simply stepping on a switch.

The number of pedals now on the market offering some flavor of distortion is staggering. Players and manufacturers generally group them under overdrive, distortion and fuzz. How can we distinguish one from another?

Way Huge founder Jeorge Tripps has the skinny for you below.

First, let’s talk about harmonics. When you play a note on your guitar, the sound you hear is made up of a fundamental frequency—the pure note—along with multiples of that frequency, which are called harmonics. If you feed your instrument’s signal into any device that changes the signal’s harmonic content in a certain fashion, you get the sound that we call distortion. There are numerous ways to change the harmonic content of your signal, but for our purposes we only need to look at three of them. Each changes harmonic content by generating additional frequencies.

The first way to generate harmonic content is to push your instrument’s signal, which is the voltage generated by your guitar’s pickups, beyond an amp or pedal’s headroom. In this context,  your instrument signal sits between two boundaries called rails. The space between the rails—how much the signal is able to swing—is called headroom. If the signal is amplified so that its peaks push against the rails, those peaks start to get clipped off of your signal. This is, very basically, how tube amp distortion is created.

The second way is to have a pedal’s circuit clip your signal well before it exceeds headroom, and the third way is to use transistors, which generate extra harmonics because of their nature as imperfect amplifiers. Most pedals use these one of these two methods—they rarely create distortion by pushing your signal past their headroom.

Each of these methods create distortion, an umbrella that covers overdrive, distortion and fuzz. The difference is a matter of degree—how much are you clipping your signal? Before we get more specific, take a look at this undistorted signal:

Now let’s look at how distortion pedals work and what they do to your signal visually.

Overdrive is the sound you get when you crank a tube amp to that rich, gritty sweet spot. There’s not a lot of clipping happening here.

Overdrive pedals are, to an extent, designed to emulate that sound, but they’re also designed to complement it. Through a clean amp, you’ll get smooth, mellow grit. If you use an overdrive pedal with a slightly dirty tube amp, you’ll stack the gain from both and get a very thick and saturated sound that’s closer to distortion but still retains the tubey warmth of your amp.

In general, overdrive circuits first use op-amps—hi-fidelity amplifiers—to add gain (boost) to your signal. After a certain level of gain is added, diodes are triggered to soft-clip the boosted signal, generating harmonic content. Check out the MXR Custom Badass Modified O.D. for an example of this type of circuit. For an atypical overdrive circuit, check out the Way Huge Red Llama, which simply slams your signal with enough gain to push it beyond the pedal’s headroom; no diodes necessary.

Distortion is the middle ground—your signal gets clipped harder than with overdrive but it’s still more articulate than fuzz. Distortion pedals produce a lot of gain, so you generally use them with a clean amp.

As with overdrive pedals, distortion pedals tend to use op-amps and diodes. The MXR Custom Badass ’78 Distortion is a great example of this type of circuit; the Way Huge Fat Sandwich uses a modified version.

Note: the trippy shape of this distortion wave has a lot to do with the pedal’s EQ, which can have as much to do with the sound of a pedal as distortion does. There are countless pedals on the market with op-amp+diode circuits, but what gives them their own voices is the way they’re EQ’d. That’s another article, though.

Fuzz pedals are designed to sound much like a faulty amplifier or an amp into a damaged speaker. Amp settings don’t matter much at this point—your signal is getting totally clipped.

These pedals are equipped with the aforementioned transistors, which need very little help to clip your signal since they add their own harmonic content as soon as they amplify your signal. The type of transistor a fuzz circuit uses can drastically affect fuzz tone. Generally speaking, germanium transistors produce a warmer and smoother fuzz while silicon transistors produce a brighter, harsher fuzz.

Some fuzz circuits go for even more clipping by using diodes in a similar way to overdrive and distortion circuits.

The standard Dunlop Fuzz Face is a classic example of a circuit that only uses germanium transistors, while the MXR Classic 108 Fuzz is an example of a fuzz with only silicon transistors. The Way Huge Swollen Pickle, on the other hand, is a great example of a fuzz that uses transistors (silicon) and diodes.

The science of distortion can seem pretty esoteric, but in simple terms we can see that the differences between overdrive, distortion and fuzz have to do with how hard you clip your signal. Depending on the shade of distortion you’re looking for, you’ll find amps and pedals using various methods to throw your signal into dirt mode.

Sacado del Blog de Jim Dunlop: http://www.jimdunlop.com/

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