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Software Tech: Amp Sims Go Pro

Craig Anderton explores how amp sims are winning over the normally conservative world of pro guitar players, both in the studio and for live performance.

When amp sims appeared a couple decades ago, opinions were divided. While the convenience of a plug-in or hardware box that could emulate the sound of various amps and effects was appealing, the sound quality was often problematic. Although you could pre- and post-process the sims for better tone, and those listening to a complete mix often couldn’t tell the difference between a recorded sim and a physical amp, for many players, the “feel” wasn’t the same.

But times have changed. There are several reasons why amplifier emulation is winning over the normally conservative world of pro guitar players, both in the studio and for live performance.

More powerful processors and more complex algorithms: Modeling amp distortion is challenging, and the algorithms needed to provide sufficient detail require today’s fast processors. The increase in sound quality has been incremental, but when you compare older amp sim programs to newer ones, the difference is obvious. For example, Waves GTR amp models were some of the earliest sims, and they were well-received at the time, but the company’s latest PRS “Supermodels” are audibly better and respond more like playing a physical amp. You’ll hear similar improvements with earlier and later models from IK Multimedia, Overloud and others.

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Oversampling and higher sample rates: Amp sims can generate harmonics above 44.1 and 48 kHz, so running projects at 96 kHz and higher helps reduce aliasing. Most amp sims include oversampling options to “fake” higher clock rates, at the expense of somewhat higher CPU consumption.

Profiling: The Kemper Profiling Amp started a revolution that is ongoing, and was the breakthrough many professionals were waiting for. The reality of tube amps is that they aren’t perfect: tubes age, matched tubes become unmatched, bias requires adjusting, and amps need to be miked properly—which is not always easy on stage. Kemper decided not to emulate amps through conventional means, but instead devised a way to capture their salient characteristics by sending test signals through an existing amp. Capturing and analyzing these test signals allows the creation of a “profile” of how the amp responds to different input signals and control settings.

At first, some thought this approach was limited compared to software that could emulate dozens of amps; however, as more users developed amp profiles (both for sale and for free), a Kemper could reproduce the sound of any amp that had been profiled properly. Producer Michael Wagener, known for his Platinum album-level work with metal bands like Dokken, Metallica, Alice Cooper, Megadeth, Mötley Crüe, Poison and others, is a tone fanatic—but after profiling his amps, he sold most of them because the Kemper’s sound was equally good, and more consistent.

Profiling is now part of amp sims, too. Positive Grid’s Amp Match feature does profiling, as does the upcoming Amp Cloner from AMR (formerly part of Peavey). I’ve even used this technique to profile amp sims proprietary to specific DAWs that I wanted to use in other DAWs. The first time I tried this, I thought I’d copied the original audio file by mistake—but there was no mistake. The sound was essentially identical.

The rise of impulse responses: The art of capturing impulses for convolution-based processing is becoming more refined, and amp sim speaker cabinets are among the beneficiaries. What’s more, newer sims often allow loading custom impulse responses. For example, if you really like a particular impulse of a Celestion speaker in a closed-back cabinet, you can use it in more than just one particular amp sim.

A change in attitude: Finally, more people accept that amp sims don’t exist solely to replace physical amps, but to provide options that would be difficult to implement with hardware. Furthermore, there’s an understanding that the virtual and physical worlds can complement each other. Some use only the effects in amp sims along with physical amps, while others use analog effects with virtual amps and cabinets. Techniques like multiband processing, stacking multiple cabinets and the like are daunting in the physical world, but take only a few mouse clicks in a virtual one. Couple that with ever-improving sound quality and it’s not surprising that amp sims have turned the corner for professional use.

There’s a great quote from Jason Burns: “If I traveled back to 1973 and stole all of Jimmy Page’s gear, but left him with an AxeFX II, Led Zeppelin III would still be Led Zeppelin III.” Amen. The art will always be more important than the tools, but it’s even better when tools advance the state of the art.

Craig Anderton’s free educational web site, www.craiganderton.org, is now online as a companion to the www.craiganderton.com digital storefront.

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