Adapted from the book Guitar Effects Pedals: The Practical Handbook (Backbeat Books/Hal Leonard)
We have already discussed the basic concepts of gain-based effects, and in the previous installment we examined boosters and compressors in detail. This time out let’s get down to the dirty: overdrives, distortions, and fuzzes.
Confusion sometimes revolves around the distinctions between overdrives, distortions and fuzzes, but in theory each should do approximately what it says on the box—even if some also do a little of the other breeds’ jobs along the way. In the case of overdrive pedals, the intention is often twofold: either to provide a gain boost to “overdrive” a tube amp into distortion, or to approximate the mildly distorted sound of a slightly overdriven tube amp. In practice, most do a little of both. Crank the average overdrive toward the max and it usually coughs up an element of self-generated distortion, which can easily be heard when DI’d into a mixing desk set to well below overload levels; generate enough distortion, and things can also sound a little fuzzy. Despite the gray areas, however, there are definitely distinctions between the types. It all makes some sense if you think in terms of the degree of clipping achieved by the pedal, with overdrives generally being soft-clipping devices and distortions being hard-clipping devices.
Most pedalheads consider the Ibanez TS-808 Tube Screamer and, to a slightly lesser extent, the TS9 which followed, to be the grandaddies of overdrive pedals—and, yes, they certainly generate an element of distortion, too. Indeed, more boutique overdrives are based on the late-1970s and early-’80s Tube Screamer template than on any other, but despite the claimed improvements and undeniable quality of many of these, original units still usually fetch far higher prices on the vintage market (ain’t it always the way?) than new units do in the stores. With all of these—and other vaguely similar units—the guts of the sound comes from a clipping amp based around the first section of a dual opamp (purists swear by the JRC4558 chip in the early Ibanez units) and a pair of clipping diodes, with transistorized buffer stages at both the input and output, and a section for tone-shaping and output level control which uses the second part of the dual opamp in conjunction with a network of capacitors and resistors.
Pedals of this template offer a sound that’s considered “natural,” “warm” and “tubey” partly by achieving smooth, symmetrical clipping, and partly by reining in harsher high harmonics that can result in sounds that are heard as jagged and spikey in other pedals. The truth is, opamps really don’t clip in the same way that tubes do, but they are manipulated in these designs to simulate a generally “tube-like” sound. Other early overdrive pedals were designed around discrete transistorized clipping and boosting circuits, though many leaned toward distortion units as properly defined, and added more artificiality to the sound—hence the Tube Screamers’ near-instant popularity when it was introduced.
MXR’s Distortion+ preceded the Tube Screamer and is an even simpler design, and, despite its name, is more an overdrive than a distortion. That said, its sound is considered by many to be a little more opaque, or colored, than the Tube Screamer’s. The box uses a 741-type IC and a pair of germanium diodes to achieve its soft-clipping sound. These are different components than the famed germanium transistors, but are made of the same material. Germanium is generally attributed a “softness” of tone, and the same applies to the diodes used in the Distortion+ (and other units); change them for silicon diodes and you’ve got a hard-clipping distortion pedal.
An overdrive is almost always at its best played through a tube amp set at medium to upper-medium volume, since the amp itself is doing a major part of the job, the pedal just being the boot that kicks its butt into juicy break-up a little quicker. Conversely, demo one DI’d into a mixing desk or portastudio as described earlier, and in most cases the breed sounds absolutely awful: harsh, raspy, cold, and artificial. It can be a shocking look at the evil side of that $350 vintage Tube Screamer you just bagged from eBay. Now stop crying, and plug it back into your AC30.
Dissatisfaction with vintage units of this type usually centers around their limited gain, and their inability to sound truly fierce with Drive cranked up to full. The more exemplary users of this type of pedal, however—such as Stevie Ray Vaughan or Eric Johnson, who were both masters of early Tube Screamers—usually kept the Drive control in the lower part of its range, where the sound remains more natural and, yet again, serves as an excellent pre-boost to drive a good tube amp into distortion when the Level control is set high enough. Some players also find older pedals built to this design to have a distinct midrange hump, a slightly wooly tonality, and/or a lack of low end (as ever, depending upon the ears of the player you talk to). Consequently, a lot of newer makers have accounted for these in their redesigns. Visual Sound’s Route 66 pedal has a Bass Boost switch, Ibanez’s own recent-era TS9DX Turbo Tube Screamer has a Mode control that takes you from classic sounds to settings with more distortion and more low end, and plenty of other makers address both in their variations on the circuit.
Fulltone’s popular Full-Drive pedal has the bonus of a switchable booster channel, while its overdrive channel goes to a fairly high gain and, unusually, uses asymmetrical clipping for a more textured sound that is quite different from the Tube Screamer’s. Asymmetrical clipping is also at the center of Boss’ SD-1 Super Overdrive (as used by Eddie Van Halen), generated by a circuit that uses two silicon diodes in series in one direction, and only one in the other, to clip each side of the waveform differently. Some players credit asymmetrical clipping with more richness, body and character; others say it sounds clanky and harsh, like an amp with mismatched output tubes. Then again, some guitarists—those in the former camp, probably—say they prefer the sound of mismatched output tubes for these same reasons. As ever, what works is up to you.
A selection of makers within the high-end, hand-built crowd of today do offer variations on the opamp-based template discussed above. Blackstone Appliances bases its Mosfet Overdrive on a discrete transistorized circuit centered around, yes, mosfets, and Klon’s Centaur pedal uses… well, who the hell knows? They cover the entire circuit board in epoxy goop to keep the cloners at bay, but this expensive overdrive certainly sounds different. Other popular boutique overdrives are found in the Barber Electronics LTD pedal, the Crowther Audio Hot Cake, and the Fulltone OCD.
By definition, distortion pedals are designed to adulterate the guitar’s signal in and of themselves. To use a rough analogy to tube amp tone, where overdrives are looking to take you into anywhere from pushed to cranked JTM45 or tweed Bassman, distortions aim to do the Mesa/Boogie Triple Rectifier, Bogner Ecstasy, or six-Laney-full-stacks trick in a 3"x5" box. These pedals unashamedly screw with your sound. They generally filth it up and slap their own notion of the ideal heavy rock or metal EQ all over your tone’s backside. But of course they will also boost the guitar signal as well (depending on the volume/output/level settings), and the sound we associate with them is still some confluence of pedal and amp, not to mention guitar.
Basic distortion boxes can be built around a simple network of transistors and clipping diodes, to both boost the signal and alter the waveform. Most units, however, very roughly resemble the standard mass-production overdrives detailed above, with the heavy work done by opamps, some tone-shaping stages, and input/output buffers. The ProCo Rat set the standard for heavy distortion sounds above and beyond the capabilities of the MXR Distortion + and the Ibanez Tube Screamer, although in fact its design is surprisingly similar to the former (discussed above), with silicon diodes in place of germanium, and an added tone control.
All mass-market brands offer at least one distortion pedal—and often many. Boss, for one, tries to cater to all possible tastes. Its DS-1 (not to be confused with the SD-1 overdrive mentioned above) is one of the workhorses of the breed, with some big-name players happy to stomp on its rectangular switch, including both Steve Vai and Joe Satriani. The DS-2 takes things a step further, while the MT-2 Metal Zone and MD-2 Mega Distortion get successively more evil. And Boss isn’t the only one, with DOD, Ibanez, Marshall and many, many others playing the game too, along with a few of the boutique makers. The proliferation is most distinctive in many “metal” pedals that go beyond even the standard distortion sounds. These generally offer the archetypal scooped-mid sound with thudding lows and crispy highs. Many are adjustable for anything from classic rock to metal sounds, with a tone control that acts more to reduce or accentuate mids rather than the usual high boost/cut, and often a “resonance” control or similar to adjust the fullness of the bass.
Other than the old cranked amp or faulty preamp channel, these are the grandaddies of distortion devices. Fuzzes were also among the first of the transistorized guitar effects being built back in the early 1960s—which is no surprise when you discover the simplicity of most of them. It’s almost pointless to describe the sound of a vintage-style fuzz tone more than the name already does. They slather a slightly wooly, rounded, warm but sparkly distortion all over the guitar signal (see, you could just say “fuzzy”) to give more meat, girth, and sustain to the sound. More imposing units can be guilty of taking charge of the entire signal and bending it to their own synthetic demands—“brick-wall processing,” as Hendrix-approved effects builder Roger Mayer puts it himself (meaning your signal hits that wall and cannot pass through without a total transformation of its nature and character)—while those which many consider to be the more playable devices retain elements of your dynamics, touch, feel, and core tonality. In the case of “brick wall” type fuzzes, the resultant sound is still, usually, more processed and artificial than any of the preceding types of pedals in this category. The more dynamic fuzz pedals, however, are great for working with you and preserving the critical elements of your touch and tone. Turn a tube amp up to where it’s starting to break up and you’ve got gentle overdrive; crank it to the max and you’ve got heavy distortion. Pull out one of the pair of output tubes, use the wrong-value bias resistor on a preamp tube, or beat it senseless with a crowbar and you might just get it to sound like fuzz. It’s not a natural sound, but it can be a great one, and it’s a major part of many players’ signature tones.
If the fuzz is the grandaddy, the Arbiter/England Fuzz Face (introduced 1966) is the grand-poobah of the grandaddies’ social club. A handful of other fuzzes came first, but this distinctive round, smiling box is the one most guitarists point to when identifying the fuzz tone of the gods. Why? Two words: Jimi Hendrix. Apparently he died and took it up there with him. Oh, and two other words: germanium transistors. When these fuzz fans point to the Fuzz Face, however, they don’t point to just any Fuzz Face. They point to a good one. The quality of these pedals varies wildly, mainly because the tolerances of germanium transistors themselves varies wildly and sorting out the good ones was more work than the makers could afford to put in (or, perhaps, knew was necessary). Contemporary makers from Fulltone to Z.Vex to Mayer take the time and trouble to laboriously sort their germanium transistors, and it pays in spades in terms of tone and consistency.
Many readers will already know that germanium has been the effects buzzword of the past many years. These transistors are considered softer, rounder, more musical. Don’t be fooled: that doesn’t mean they make music all by themselves, you have to make music through them. But that’s not such a bad thing. Open up a Fuzz Face for the first time and you’re likely to be startled by its simplicity, and other early fuzzes like Maestro’s Fuzz-Tone (1963) and Sola Sound’s Tone Bender (1965) are equally basic. As far as the Face goes, you’ll find fewer than ten components on the board, two of them being those crucial AC128 or NKT275 transistors. Interestingly, the Tone Bender originally used two OC75 germanium transistors made by Mullard, the revered British tube manufacturer.
Later makes of fuzzes—and later generations of those above—moved on to silicon transistors. Many players found the silicon-based models a little harsher sounding, however, and the legend of the magical germanium transistors began to grow. Even so, plenty of guitarists get along just fine with the silicon variety. Eric Johnson, often credited with ears of canine keenness, has used a silicon-transistor Dallas-Arbiter Fuzz Face to drive the dirty rhythm of his famous multi-amped, multi-routed set-up. He also holds the unit together with a rubber band because he says the bottom plate’s central mounting screw affects its tone. Make of this what you will.
High-end builders of today have gone back to germanium en masse for their classic fuzz tones, and most of them test their transistors to sort out the few that will do the job correctly. They put them in anything from vintage-style units—like Fulltone’s ’69, Frantone’s The Sweet, and Roger Mayer’s Classic Fuzz—to way-out updates of the breed—such as Z.Vex’s Fuzz Factory.
Next time: modulation effects.