Amplifier modeling (also known as amp modeling or amp emulation) is the process of emulating a physical

amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the v ...

such as a

guitar amplifier A guitar amplifier (or amp) 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 a ...

. Amplifier modeling often seeks to recreate the sound of one or more specific models of vacuum tube amplifiers and sometimes also solid state amplifiers.

Types of modeling devices

;Digital amp modelers :Standalone modeling devices such as the Line 6 POD (1998-) 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. Most modelers generally also include a variety of

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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 Roland (; frk, *Hrōþiland; lat-med, Hruodlandus or ''Rotholandus''; it, Orlando or ''Rolando''; died 15 August 778) was a Frankish military leader under Charlemagne who became one of the principal figures in the literary cycle known as the ...

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 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 Tech 21 is a New York based manufacturer of guitar and bass effect pedals, amps, and DI boxes which allow the user to emulate the tone of many popular guitar amps and record those sounds directly into a mixer. Products Tech 21's core produc ...

'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 workstation A digital audio workstation (DAW) is an electronic device or application software used for Sound recording and reproduction, recording, editing and producing audio files. DAWs come in a wide variety of configurations from a single software pro ...

s) 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 DSP may refer to: Computing * Digital signal processing, the mathematical manipulation of an information signal * Digital signal processor, a microprocessor designed for digital signal processing * Yamaha DSP-1, a proprietary digital signal ...

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.

References

{{reflist Instrument amplifiers