Amplifier modeling

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Amplifier modeling (also known as amp modeling or amp emulation) is the process of emulating a physical amplifier such as a guitar amplifier. Amplifier modeling often seeks to recreate the sound of one or more specific models of vacuum tube amplifiers and sometimes also solid state amplifiers.

Contents

Types of modeling devices

The Roland Micro Cube, left, a small and portable digital modeling amplifier. RolandMicroCube.jpg
The Roland Micro Cube, left, a small and portable digital modeling amplifier.
Digital amp modelers
Standalone modeling devices such as the Line 6 POD (1998-) [1] digitize the input signal and use a DSP, a dedicated microprocessor, to process the signal with digital computation, attempting to achieve the sound of expensive professional amplifiers in a much less costly and more compact device. These modelers can be connected directly to a recording device or PA system without having to use a power section, speaker cabinet and microphone; however, there is an ongoing debate over the question of how accurately a modeler can recreate the sound of a real amplifier. [2] Most modelers generally also include a variety of effects apart from the amp emulations and some can be connected via USB for computer based recording.
Digital modeling amplifiers
Modeling amps such as the Peavey Vypyr, Roland Cube, Fender Mustang, and Line 6's Spider series are amplifiers that include a built-in modeling device. Some high-end modeling amplifiers such as the Vox Valvetronix and the 60/120 watt versions of the Peavey Vypyr [3] combine the digital modeling process with actual vacuum tube amplification.
Analog emulators
Analog modeling systems also exist; in fact the first "modeling" devices were analog and utilized common analog circuitry in signal processing functions, such as filters, amplifiers, and "waveshapers". Conceptually "modeling" is an old scheme, and in essence one may regard a simple "diode clipper" waveshaper as an "emulation" of overdrive characteristics of certain (tube-based) designs. Similarly we may regard deliberate enhancement of frequency response as an emulation, assuming the emulated system likewise introduces a similarly enhanced response. During history, simple conceptual circuits of mimicking a certain attribute have topologically evolved to become more and more complex in order to provide a more "detailed" or "realistic" emulation outcome. Basically, the concept of analog signal processing is ancient but it is somewhat controversial when people began to refer to certain processing techniques as "modeling". Tech 21's SansAmp line of products (1989-) is one of the earliest examples of devices that were purposefully marketed as being capable of producing various "amplifier-specific" tones.

Digital vs analog device, DAW plugin software

Signal processing within the modeling concept can be realized with analog or digital circuitry, or combinations of them both. Digital amplifier modeling may appear as software, such as plugins for DAWs (digital audio workstations) which may be aided by computer hardware accelerators, or may be part of a standalone device or amplifier.

As part of a digital audio workstation, amplifier modeling may be applied "after the fact", to a guitar signal that was recorded "clean", in order to achieve the sound of an amplifier being used. This process has the advantage of being dynamic—the amplifier settings can be adjusted without forcing the musician to re-record the piece.

Today many analog modeling circuits may have a digitally-controlled interface, and the analog signal paths within such units are often "re-routed" and reconfigured with aid of digital logic and semiconductor-based switching circuitry. In addition, many "digital" modeling devices that employ DSP may also employ analog modeling circuits.

Other examples of modeling circuit

A good example of a moderately complex analog modeling circuit is Peavey's "T-Dynamics" power amplifier design, which (using 100% analog circuitry) emulates complex clipping and bias-shifting characteristics of push-pull tube power amplifiers, as well as the typically high-ish output impedance of such. Vox "Valve Reactor" power amplifier, Hughes&Kettner "Dynavalve" power amplifier, Mesa Boogie Triaxis Tube Preamp, Pritchard guitar amplifiers and Quilter musical instrument amplifiers are other examples of units that feature analog circuit designs of similar nature.

Roland's earliest "Blues Cube" amplifiers employed analog tube modeling circuitry, though Roland did not model specific tube amplifiers, more so the overall characteristics of a generic tube-based preamplifier circuit. Peavey's "TransTube" preamplifiers are designs of similar nature. Pritchard amplifiers also model characteristics of tube-based circuits in general and without attempt to model any "amp-specific" tones per se.

Roland and Line 6 employ analog power amplifier emulation in some of their amplifier models. Peavey's "Vypyr" series of modeling amplifiers utilises analog "TransTube" circuit instead of a digital waveshaper, and Vox Valvetronix amplifiers have throughout their history presented a marriage of semiconductor and vacuum tube -based analog modeling circuitry and digital signal processing circuitry.

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<span class="mw-page-title-main">Electronics</span> Branch of physics and electrical engineering

Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other electrically charged particles. Electronics is a subfield of electrical engineering, but it differs from it in that it focuses on using active devices such as transistors, diodes, and integrated circuits to control and amplify the flow of electric current and to convert it from one form to another, such as from alternating current (AC) to direct current (DC) or from analog to digital. Electronics also encompasses the fields of microelectronics, nanoelectronics, optoelectronics, and quantum electronics, which deal with the fabrication and application of electronic devices at microscopic, nanoscopic, optical, and quantum scales.

<span class="mw-page-title-main">Amplifier</span> Electronic device/component that increases the strength of a signal

An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal. It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a power gain greater than one.

<span class="mw-page-title-main">Effects unit</span> Electronic device that alters audio

An effects unit or effects pedal is an electronic device that alters the sound of a musical instrument or other audio source through audio signal processing.

<span class="mw-page-title-main">Audio power amplifier</span> Audio amplifier with power output sufficient to drive a loudspeaker

An audio power amplifier is an electronic amplifier that amplifies low-power electronic audio signals, such as the signal from a radio receiver or an electric guitar pickup, to a level that is high enough for driving loudspeakers or headphones. Audio power amplifiers are found in all manner of sound systems including sound reinforcement, public address, home audio systems and musical instrument amplifiers like guitar amplifiers. It is the final electronic stage in a typical audio playback chain before the signal is sent to the loudspeakers.

<span class="mw-page-title-main">Vox (company)</span> Musical equipment manufacturer

Vox is a British musical equipment manufacturer founded in 1957 by Thomas Walter Jennings in Dartford, Kent, England. The company is most famous for making the Vox AC30 guitar amplifier, used by The Beatles, The Rolling Stones, The Kinks, The Yardbirds, Queen, Dire Straits, U2, and Radiohead; the Vox Continental electric organ, the Vox wah-wah pedal used by Jimi Hendrix, and a series of innovative electric guitars and bass guitars. Since 1992, Vox has been owned by the Japanese electronics firm Korg.

<span class="mw-page-title-main">Analog synthesizer</span> Synthesizer that uses analog circuits

An analogsynthesizer is a synthesizer that uses analog circuits and analog signals to generate sound electronically.

<span class="mw-page-title-main">Guitar amplifier</span> Electronic amplifier for musical instruments

A guitar amplifier is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which are typically housed in a wooden cabinet. A guitar amplifier may be a standalone wood or metal cabinet that contains only the power amplifier circuits, requiring the use of a separate speaker cabinet–or it may be a "combo" amplifier, which contains both the amplifier and one or more speakers in a wooden cabinet. There is a wide range of sizes and power ratings for guitar amplifiers, from small, lightweight "practice amplifiers" with a single 6-inch speaker and a 10-watt amp to heavy combo amps with four 10-inch or four 12-inch speakers and a 100-watt amplifier, which are loud enough to use in a nightclub or bar performance.

<span class="mw-page-title-main">Preamplifier</span> Electronic amplifier that converts weak signal into strong signal

A preamplifier, also known as a preamp, is an electronic amplifier that converts a weak electrical signal into an output signal strong enough to be noise-tolerant and strong enough for further processing, or for sending to a power amplifier and a loudspeaker. Without this, the final signal would be noisy or distorted. They are typically used to amplify signals from analog sensors such as microphones and pickups. Because of this, the preamplifier is often placed close to the sensor to reduce the effects of noise and interference.

<span class="mw-page-title-main">Peavey Electronics</span> American audio equipment manufacturer

Peavey Electronics Corporation is an American company which designs, develops, manufactures and markets professional audio equipment. It is one of the largest audio equipment manufacturers in the world, and is headquartered in Meridian, Mississippi.

PS Audio is an American company specializing in high-fidelity audio components equipment for audiophiles and the sound recording industry. It currently produces audio amplifiers, preamplifiers, power related products, digital-to-analog converters, streaming audio, music management software and cables.

Line 6 is a musical instrument and audio equipment manufacturer, best known as a pioneer in guitar amplifier and effect modeling. The company's products include guitar effects, modeling guitar amplifiers, Software, |electric guitars, and wireless systems. Line 6 has an active user community, and provides software that allows users to easily download and share patches or device settings for many of the company's products. Founded in 1996 and headquartered in Calabasas, California, the company has been a subsidiary of Yamaha Corporation since 2014.

<span class="mw-page-title-main">Linear amplifier</span> Electronic circuit

A linear amplifier is an electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. The term usually refers to a type of radio-frequency (RF) power amplifier, some of which have output power measured in kilowatts, and are used in amateur radio. Other types of linear amplifier are used in audio and laboratory equipment. Linearity refers to the ability of the amplifier to produce signals that are accurate copies of the input. A linear amplifier responds to different frequency components independently, and tends not to generate harmonic distortion or intermodulation distortion. No amplifier can provide perfect linearity however, because the amplifying devices—transistors or vacuum tubes—follow nonlinear transfer function and rely on circuitry techniques to reduce those effects. There are a number of amplifier classes providing various trade-offs between implementation cost, efficiency, and signal accuracy.

<span class="mw-page-title-main">Bass amplifier</span> Electronic amplifier for musical instruments

A bass amplifier is a musical instrument electronic device that uses electrical power to make lower-pitched instruments such as the bass guitar or double bass loud enough to be heard by the performers and audience. Bass amps typically consist of a preamplifier, tone controls, a power amplifier and one or more loudspeakers ("drivers") in a cabinet.

<span class="mw-page-title-main">Distortion (music)</span> Type of electronic audio manipulation

Distortion and overdrive are forms of audio signal processing used to alter the sound of amplified electric musical instruments, usually by increasing their gain, producing a "fuzzy", "growling", or "gritty" tone. Distortion is most commonly used with the electric guitar, but may also be used with other electric instruments such as electric bass, electric piano, synthesizer and Hammond organ. Guitarists playing electric blues originally obtained an overdriven sound by turning up their vacuum tube-powered guitar amplifiers to high volumes, which caused the signal to distort. While overdriven tube amps are still used to obtain overdrive, especially in genres like blues and rockabilly, a number of other ways to produce distortion have been developed since the 1960s, such as distortion effect pedals. The growling tone of a distorted electric guitar is a key part of many genres, including blues and many rock music genres, notably hard rock, punk rock, hardcore punk, acid rock, and heavy metal music, while the use of distorted bass has been essential in a genre of hip hop music and alternative hip hop known as "SoundCloud rap".

<span class="mw-page-title-main">Guitar speaker</span>

A guitar speaker is a loudspeaker – specifically the driver (transducer) part – designed for use in a combination guitar amplifier of an electric guitar, or for use in a guitar speaker cabinet. Typically these drivers produce only the frequency range relevant to electric guitars, which is similar to a regular woofer type driver, which is approximately 75 Hz — 5 kHz, or for electric bass speakers, down to 41 Hz  for regular four-string basses or down to about 30 Hz for five-string instruments.

<span class="mw-page-title-main">Fender Champ</span>

The Fender Champ was a guitar amplifier made by Fender. It was introduced in 1948 and discontinued in 1982. An updated version was introduced in 2006 as part of the "Vintage Modified" line.

<span class="mw-page-title-main">Peavey 5150</span>

The Peavey 5150 is a vacuum tube based guitar amplifier made by Peavey Electronics from 1992 on. The amplifier was initially created as a signature model for Eddie Van Halen. After Van Halen and Peavey parted ways in 2004, the name was changed to Peavey 6505 in celebration of Peavey's 40th anniversary (1965–2005). The 5150 name was used again by Van Halen in partnership with Fender under the EVH brand in 2007 and 2011.

<span class="mw-page-title-main">Tube sound</span> Characteristic quality of sounds from vacuum tube amplifiers

Tube sound is the characteristic sound associated with a vacuum tube amplifier, a vacuum tube-based audio amplifier. At first, the concept of tube sound did not exist, because practically all electronic amplification of audio signals was done with vacuum tubes and other comparable methods were not known or used. After introduction of solid state amplifiers, tube sound appeared as the logical complement of transistor sound, which had some negative connotations due to crossover distortion in early transistor amplifiers. However, solid state amplifiers have been developed to be flawless and the sound is later regarded neutral compared to tube amplifiers. Thus the tube sound now means 'euphonic distortion.' The audible significance of tube amplification on audio signals is a subject of continuing debate among audio enthusiasts.

<span class="mw-page-title-main">Keyboard amplifier</span>

A keyboard amplifier is a powered electronic amplifier and loudspeaker in a wooden speaker cabinet used for the amplification of electronic keyboard instruments. Keyboard amplifiers are distinct from other types of amplification systems such as guitar amplifiers due to the particular challenges associated with making keyboards sound louder on stage; namely, to provide solid low-frequency sound reproduction for the deep basslines that keyboards can play and crisp high-frequency sound for the high-register notes. Another difference between keyboard amplifiers and guitar/bass amplifiers is that keyboard amps are usually designed with a relatively flat frequency response and low distortion. In contrast, many guitar and bass amp designers purposely make their amplifiers modify the frequency response, typically to "roll-off" very high frequencies, and most rock and blues guitar amps, and since the 1980s and 1990s, even many bass amps are designed to add distortion or overdrive to the instrument tone.

In electronics, power amplifier classes are letter symbols applied to different power amplifier types. The class gives a broad indication of an amplifier's characteristics and performance. The first three classes are related to the time period that the active amplifier device is passing current, expressed as a fraction of the period of a signal waveform applied to the input. This metric is known as conduction angle (θ). A class A amplifier is conducting through all the period of the signal (θ=360°); Class B only for one-half the input period (θ=180°), class C for much less than half the input period (θ<180°). Class D amplifiers operate their output device in a switching manner; the fraction of the time that the device is conducting may be adjusted so a pulse-width modulation output can be obtained from the stage.

References

  1. "Line 6".
  2. "Respectful Disagreement: Modeling Amps". 17 October 2013.
  3. "Archived copy". Archived from the original on 2016-02-02. Retrieved 2016-02-02.{{cite web}}: CS1 maint: archived copy as title (link)