Although confusion sometimes revolves around the distinctions between overdrives, distortions and fuzzes, in practice they 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, it essentially has one of two jobs: either to provide a gain boost to “overdrive” a tube amp into distortion (true overdrive), or to approximate the mildly distorted sound of a slightly overdriven tube amp (more akin to a distortion pedal). Most actually do a little of both. Crank the average overdrive toward the max and it usually churns out 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, 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 players 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. Without a doubt, 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 clones, original units still usually go for far higher prices on the vintage market than new pedals do in the stores. With all of these—and other vaguely similar pedals—the root 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 bringing 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 distinct transistorized clipping and boosting circuits, although many used methods more akin to true distortion pedals and added in some artificial sound, which is why the Tube Screamer’s more realistic tube sound made it a near-instant success when released. MXR’s Distortion+ - which came out before the Tube Screamer – is made of an even simpler design, and is actually 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 (which is what many of today’s modern fuzzes and distortion boxes use) 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. Meanwhile, try one DI’d into a mixing desk and in most cases the breed sounds absolutely awful: harsh, raspy, cold, and artificial. I can’t even imagine how many players have dropped $400 on a vintage Tube Screamer only to find out it sounded like crap when plugged into a solid state amp or directly into a recording console!
Moving on, the biggest complaints with vintage units of this type usually revolve around their limited gain, along with their inability to sound truly fierce with Drive cranked up to full. The more ideal 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 (depending on the player you talk to). Therefore, 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 a lot 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 always, what works for you is up to you.
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