A distortion is a device or software for deforming an audio signal with a limiter or other forms of characteristic curve deformation , with harmonic overtones ultimately being generated. The deformation can be (non) linear , symmetrical or asymmetrical change .
With modern guitar or bass amplifiers there are various setting options for how individual components of the signal can be distorted. Effects devices enable distortion before the amplifier; Software the subsequent distortion. With musical instruments, playing techniques such as flageolet tones can be emphasized.
A basic distinction is made between harmonic and non-harmonic distortion. There are significant tonal differences between tube and transistor distortion units as well as germanium and silicon transistors, especially their circuitry. Depending on the intensity of the effect, a distinction is made between overdrive, distortion and fuzz boxes . They are also used for vocals , electric bass , synthesizers or drums .
Originally produced the oversteer with one of the steps, especially the output stage of a tube - guitar amplifier this sound by the amplifier is played on the upper power limit. From a technical point of view, this behavior of the low- power amplifiers of the time was not desired. In the late 1950s, bands sometimes deliberately "destroyed" amplifiers or speakers to achieve the effect. The desire to produce distorted sounds non-destructively even at lower volumes led to the development of the distortion effects device independent of the guitar amplifier in the early 1960s.
Since an overdriven transistor amplifier stage has a different sound character than an overdriven tube amplifier stage, semiconductor effect circuits were developed . They mimic the sound of tube distortion. From a technical point of view, there are several ways to distort a signal: In addition to the transistor distortion device already mentioned, referred to by the manufacturers as Fuzz , two anti-parallel connected diodes in the signal path can produce a distortion similar to that of a tube amplifier (picture). Due to the characteristic curve of the diodes, the positive and negative signal half-wave is flattened at the peaks or, depending on the characteristic curve of the diode and the level of the input voltage, is dynamically limited, which makes it sound distorted. As a further variant, amplifier stages with field effect transistors in the non-linear characteristic range are used, which produce harmonic overtones with their soft limitation. Based on this principle, another variant was developed in which CMOS operational amplifiers are supplied with a dynamically limited operating voltage and, with simultaneous overdrive, they are deliberately allowed to work in the non-linear range, which leads to the desired distortions. All circuit variants can be combined with one another. In connection with a different sound filtering, almost countless circuit variants are possible, each sounding different.
If different frequencies are fed into a distortion at the same time, according to the laws of mixing , new combination frequencies and harmonics are created that were not included in the original frequency mix . Their relative strength depends on how much the characteristic curve deviates from the straight line.
Since the end of the 1990s, distortion effects have also been achieved with the method of digital signal processing : the input signal , which is initially digitized, is subjected to a digital signal processing process that mathematically reproduces the distortion and then converts it back into analog signals.
Originally, the volume of tube guitar amplifiers could only be adjusted via the power amplifier. In order to control the output stage (engl. Overdrive ) and distort it, the volume control in the upper region or until it has been rotated to the stop. For this reason, Jim Marshall developed the first guitar amplifier with a master volume control in 1975. With this it was possible for the first time to set the gain of the preamp separately (i.e. also to overdrive) and to distort the guitar signal before the output stage. The master volume control could now be used to set the overall volume. This achieves more distortion at a lower volume. As a further development, additional amplifier stages in the pre-stage advanced the distortion sound.
Manufacturers often refer to the original distortion sound as overdrive , while the stronger (pre-stage) distortion sound is usually called distortion. The overdrive sounds a little softer and more “dirty”, whereas the distortion sounds more “aggressive” and “pointed”. Since overdrive and distortion shape the sound and the type of distortion differently, corresponding distortions are often categorized accordingly. In fact (or originally) both terms actually mean the same thing, with overdrive describing the origin and distortion describing the result of this sound.
With corresponding devices, the respective rotary adjuster / switches stand for the corresponding type of distortion or distortion to be imitated:
- Gain, Boost, Level: Affects the degree of amplification before the distortion stage,
- Dist: Represents the simulated pre-amp distortion,
- Drive, Overdrive: Stands for the simulated output stage distortion.
In some cases, there are sound controls on the devices that make it possible to distort only certain frequency ranges or to filter out frequency components from the distorted sound.
Distortion devices are used as sound effects in music production. The distortion can be heard as guitar effects, especially in rock music . It should be noted that distortion devices do not only have the typical electric guitar sound, but are only one link in the chain guitar-distortion-amplifier-loudspeakers, which sound different in their respective constellations. Distortions on the drums, bass or vocals can often be heard in drum and bass or industrial . The distorted blues harp found its breakthrough in the Chicago blues . Even today this instrument is mostly played slightly distorted.
The TS-808 Tube Screamer (first used in 1976, since then used by countless guitarists, including Carlos Santana ). This was followed by TS-9 Tube Screamer ( Kenny Wayne Shepherd ) TS Mini, TS808DX with Boost and various, each slightly modified models. Original TS-808s from the 1970s are sold at high prices. There are "shootouts" or comparisons of the models and also about custom modifications among other things on various video portals.
- Steve Vai Gemini Distortion Pedal
- Ibanez Sonic Distortion
The OD-1 from Boss (1977 to 1985 " state of the art ") is now traded at high prices. The older models can be recognized by the fact that the "O" of OD-1 is exactly below the second "r" of Over-Drive. Old models are already trading for $ 200 and more. Was replaced by the OD-2 in 1985, the current model is now the OD-3 (since 1998).
- DS-1 Distortion by Boss ( Kurt Cobain , Steve Vai , Joe Satriani , John Frusciante ), in production since 1978.
- DS-2 TURBO Distortion by Boss ( Kurt Cobain from the 1992 tour, John Frusciante )
- BOSS MD-2 Mega Distortion, MT-2 Metal Zone, BD-2 Blues Driver
- Throttle box
- Flux-Drive and Flux-Five Overdrive +
The Big Muff is available in different Russian and American versions (Rams Head, Triangle, Green Muff, Black Muff ...)
- Electro-Harmonix Big Muff ( Rick McPhail , Munky / Head (Korn), David Gilmour, J. Mascis)
- ProCo RAT ( John Scofield , David Gilmour , James Hetfield )
- Smash box.
- Fulltone Full-Drive 2, OCD
- Zoom Power Drive
- Digitech Tone Driver
- Sansamp GT2 (actually a complete analog amp / speaker simulator on semiconductor basis)
- ZVex Box of Rock
- Baldringer DualDrive
- COOL PEDALS Dirty Devil
- Frank Pieper: "The Effects Practice Book". 2nd edition, Carstensen Verlag, Munich, 2004, ISBN 3-910098-27-4
- Roland Enders: The home recording manual. 3rd edition, Carstensen Verlag, Munich, 2003, ISBN 3-910098-25-8
- Helmuth Lemme: electric guitar sound. 1st edition, Richard Pflaum Verlag, Heidelberg, Munich, 1994, ISBN 3-7905-0675-3
- Gustav Büscher, A. Wiegemann: Little ABC of electroacoustics. 6th completely revised and expanded edition. Franzis Verlag, Munich 1972, ISBN 3-7723-0296-3 ( Radio-Praktiker-Bücherei 29 / 30a).
- Helmuth Lemme: Guitar amplifier sound. 1st edition, Richard Pflaum Verlag, Heidelberg, Munich, 1995, ISBN 3-7905-0717-2
- Siegfried Wirsum: Practical sound reinforcement technology. Device concepts, installation, optimization. Franzis-Verlag GmbH, Munich 1991, ISBN 3-7723-5862-4 .