How Guitar Modeling Companies Are Recreating Rare Vintage Sounds for the Digital Age.

By 2009, Dweezil Zappa faced a challenge related to space. During his tours in the United States, he performed songs by his father, Frank Zappa, and to recreate those distinctive sounds, he needed to transport very bulky equipment, comparable in size to two large refrigerators, with over 200 connections and cables. Dweezil explained that his challenge on tour was to find a way to reproduce those sounds without the original equipment his father used, as part of it was no longer available. In this context, he began to explore in-depth an emerging technology: guitar amplifier modelers.

These devices, the size of a suitcase, aim to capture the essence of the sounds of analog amplifiers and pedals, reinterpreting them digitally and offering audio quality comparable to that of the original equipment. Zappa realized that modelers not only represented a solution to save space but also provided him with a new dimension of creativity. With proper adjustments, he could access almost any sound or effect he imagined at will. "If I have to switch to another song during a set that's from 1981, I just press a button," he noted. "It's like having a recording studio, the entire recording chain, at your feet."

Digital or "simulated" amplifiers are generally classified into two categories: profilers and modelers. Profilers take a sound snapshot of a guitar setup and convert it into code, allowing the tone to be reproduced without the need for the physical equipment. These can be played through a real amplifier or, more commonly, through a speaker system. In contrast, modelers analyze the tonal characteristics of an amplifier at a granular level and replicate each of its components digitally. This process simulates practically every tube, preamp, and transformer, creating a digital "twin" made up of ones and zeros.

The goal in both cases is to take the signal from an instrument, convert it to a digital format, and process it through the digital amplifier, adding complexity and tonal richness. Although they are not exact copies of their analog counterparts, most people, except professional musicians and audio engineers, will not notice the difference, especially in a live environment.

The components of these devices vary widely, but they mostly include digital signal processing (DSP) chips and integrated circuits, employing specialized algorithms to replicate the sound and behavior of different amplifiers and effects. Audio processing tools, such as wave shapers, manipulate the waveforms to recreate the saturation that occurs in analog amplifiers when vacuum tubes are overdriven. In analog amplifiers, this physical process generates distortion, a defining characteristic that shapes the unique tonal qualities of an amplifier. Modelers replicate this effect by introducing audio clipping through digitally manipulated sound waves, effectively imitating the distortion present in analog circuits.

The rapid innovation and competition in amplifier modeling technology over the last decade have made it a staple in modern recorded music. Furthermore, modelers are gaining traction in live performances, a shift that industry experts attribute to the increased frequency of tours and the growing acceptance among veteran guitarists. New-generation musicians may never get to play a "real" tube amplifier. With modelers, they can experience digital recreations of vintage or rare sounds they otherwise would not have access to. In some cases, amplifier modelers can even allow more obscure musical gear to live on digitally long after the original pieces and possibly the people who know how to maintain them have vanished.

This sector is largely dominated by products from companies like Fractal Audio Systems, Line 6, Neural DSP, and Kemper. Neural DSP employs a robotic operator with a microphone to capture audio recordings of a rig fine-tuned incrementally, processing that data through an audio interface. Its Quad Cortex device includes a "capture" function that allows musicians to connect their own analog setup and create a convincing digital replica in minutes. Fractal Audio, whose modeler Zappa uses, utilizes schematics and blueprints of analog amplifiers to generate digital versions of individual components like transformers and tubes. The ultimate goal, according to Matt Picone, the corporate development manager at Fractal Audio, is to build "virtual gear" that functions almost identically to its analog inspiration.

For most non-musicians, the difference in audio fidelity between an analog amplifier and a modeler is imperceptible, and it has been so for several years. However, some musicians feel that modelers, no matter how sophisticated, still fail to match an essential human quality. Dave Friedman, a veteran amplifier designer who has created custom gear for guitarists like Eddie Van Halen and Jerry Cantrell, stated in an interview that modelers are excellent tools that can achieve good tones, but he worries they limit the interaction between the performer and the amplifier. "There's an impact that real gear has that the modeler doesn't," Friedman asserted. "There's no danger."

However, both Zappa and Carter argue that the new generation of advanced modelers meets expectations in terms of audio fidelity, realism, and feel. Zappa currently uses a modeler on a tribute tour for Jimi Hendrix. Carter notes that many of the reservations of "tone purists" are diminishing thanks to these improvements. "We've reached a point where even the best guitarists in the world, when presented with their touring gear for 40 years and the modeler, many of them end up preferring the modeler, not just for how it sounds, but also for the creative freedom it offers," he comments.

It is worth mentioning that both Carter and Zappa still have an affection for tube amplifiers. Carter compares the situation to an old classic car versus a new electric vehicle. The former is beautiful and nostalgic, although it may not necessarily be the best tool for daily use. While these amplifiers are iconic, they are susceptible to damage, heavy, and expensive, and have limitations in their operation. All these considerations push toward a transition to more modern technologies.

Today, the growing use of modelers is associated with the increasing importance of touring in the music industry. Artists of all sizes are traveling more than ever, and one of the biggest expenses is transporting equipment. “Every major tour that has switched to [modelers] has saved a lot of money on transport,” Carter asserts. Additionally, modelers are considerably more durable and less prone to failure than bulky analog gear. Components of tube amplifiers can break easily during transport, resulting in variable sounds every day. This was evident when Metallica experienced issues with their gear during a concert in Antarctica in 2013, where solar power was insufficient for their traditional equipment, but adequate for a Fractal modeler.

More than ten years later, Metallica's guitarist, Kirk Hammett, still uses a variant of that same modeler. “I have a studio-quality sound on my Fractal,” he commented. “An album-quality sound. That's something hard to achieve.” Veteran musicians are not the only ones benefiting from the vintage tones captured in modern modelers. New artists, who in many cases could not afford a vintage 70s Fender amplifier, can now enjoy a close replica of that sound by connecting their guitar to a modeler. This is possible in part because amplifier companies cannot patent or trademark a specific sound, allowing model maker companies to create digital recreations of classic amplifiers with slightly altered names that pay homage to their analog ancestors. The result is that new artists can preserve and continue the iconic sounds of the past, even as the original equipment that produced them fades into obsolescence.