Stack in the Box

After its introduction in 1998, Line 6's Pod probably did more to popularize the concept of digital guitar-amp modeling than any other product. But another
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After its introduction in 1998, Line 6's Pod probably did more to popularize the concept of digital guitar-amp modeling than any other product. But another Line 6 modeling product, Amp Farm — a TDM plug-in for Digidesign's Pro Tools that was released before Pod — also had a major impact. So impressive was Amp Farm that it created a new market among users of native DAW applications, who yearned for amp-modeling software compatible with their platforms.

But when such products began to appear, the response was not universal acceptance. Besides the usual authenticity argument that purists make about all digital modeling products, the biggest drawback was the latency inherent in native systems. (Latency is less of an issue on TDM systems, because the audio processing is done on a dedicated DSP card rather than in the host computer's CPU.)

In a direct-recording scenario, latency results because the signal from the guitar has to pass through the A/D converter hardware and the audio buffer set in the software, and then come back through the D/A converters. That journey causes a delay between when the guitarist hits a note and when the computer outputs the processed sound.

On the older, slower computer systems of several years ago, latency was noticeable enough that guitarists found the experience of playing through native modeling software to be less than satisfying — no matter how many cool sounds and effects there were.

Improved Performance

The good news is that nowadays, processing speed has significantly increased and audio hardware can operate well at small buffer settings. As a result, latency can be reduced to almost imperceptible levels. With that hurdle cleared, native DAW users now can enjoy the benefits of guitar-amp modeling software just as their TDM contemporaries can.

After all, what guitarist wouldn't want to have dozens of amplifiers available at the press of a button? Having amp-modeling software is a lot less expensive than owning a collection of vintage amps, and you don't have to worry about storage or maintenance or disturbing family, pets, or neighbors with late-night playing. Another advantage is that you can choose to record your guitar unprocessed and then use your amp-simulator software to shape the tone during mixdown, essentially reamping your guitar sound to fit the song.

Guitar-amp plug-ins are not just for guitarists, however. Keyboardists, vocalists, and bassists have often experimented with their sound by running their instruments through guitar amps. Now they too can experience the same flexibility using software.

The Lineup

The following are reviews of five amp-modeling plug-ins for guitarists: Alien Connections ReValver, IK Multimedia Amplitube, MDA Combo, Native Instruments Guitar Rig, and Nomad Factory Rock Amp Legends. The criteria for inclusion in this roundup were that the software must run native and be available for use in multiple hosts. Four of the five products reviewed are cross-platform, and ReValver is for Windows only.

For one reason or another, a number of other guitar-amp modeling products on the market didn't meet the criteria for this roundup. They include products (like Amp Farm) that run on DSP cards (TDM, TC Electronic's PowerCore, and Universal Audio's UAD-1) or are exclusive to a single application. I provide coverage of many of those programs in the “Accelerated Amps,” “Amp Sims in Pro Tools,” and “Apples and Apples” sidebars.

Alien Connections

ReValver (Win, $99)
Alien Connections ReValver was one of the earliest guitar-amp simulation plug-ins to be released. Its interface features a virtual rack into which you place components called Modules. Each Module represents a different virtual component such as a preamp, a power amp, a speaker cabinet, a chorus, a flanger, an auto wah, a delay, and so forth.

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FIG. 1: Alien Connections' ReValver lets you create a guitar amp from its virtual Modules.

You can add as many as 16 Modules to your rack (depending on you CPU's available processing power), but there are some limitations to the order in which they appear in the signal chain. Effects can be placed only at the beginning or end; preamp simulations must come before power amps, power amps must come before speakers, and speakers must come before room simulations. Only Trim Pot modules and Parametric Filter Modules have no limitations on where they're placed in the chain. If you want, you can create racks consisting of only one type of Module, such as a speaker simulator. You can create presets of entire rack configurations, or you can make presets for each Module.

ReValver offers an extensive collection of components. Fourteen preamp Modules are available, including unique ones for most genres (pop, country, and metal) and amp types (solid state and valve). The eight power amps cover those same genres and amp types.

Nowhere is it mentioned which specific makes and models of preamps or amps are being emulated. ReValver furnishes more than 20 speaker simulations, with some cabinets modeling a specific type (such as the 158 '60s Fender Tweed Champ), but most emulate only generic speaker configurations (2512, 4512, and so on).

Effects and dynamics-processor Modules include four types of stereo reverb (only one referred to as being “high quality”), three varieties of echo/delay, two noise gates, a chorus/flanger, a compressor, tremolo, parametric EQ, 9-band graphic EQ, and room simulator. As long as you follow ReValver's rules of Module order, you can create mind-numbing combinations (see Fig. 1).

I wasn't able to find any Module combinations that sounded like specific classic amps. None of the presets are named for actual amps, and ReValver has no facility for picking a preamp, amp, and speaker combination that's designated to sound like a specific amp. That isn't necessarily a bad thing, but it means if you have a certain sound in mind, it may be difficult to re-create it.

Since most of the preamp Modules are geared to one type of sound (heavy metal, clean valve preamp, and so on), if you change your mind about the tone you want, you'll need to swap preamps. Most of the simulations don't respond well to playing dynamics, and most don't sound particularly tubelike, but some of the lower-gain sounds have a nice bite and edge to them (see Web Clip 1). The effects are all usable. None are exceptional, but none are poor. The Fender speaker models sound particularly realistic.

ReValver is far less expensive than any of the other commercially available products reviewed here, and if you are looking for an inexpensive, DX-format plug-in that models amps and effects and offers lots of flexibility, ReValver just might fit the bill.

Pros Large selection of Modules with many combinations possible. Inexpensive.

Cons Limited Module-routing possibilities. Simulations don't respond well to playing dynamics. Most sounds don't model specific guitar amplifiers.

Compatibility Windows: DirectX.

IK Multimedia

Amplitube 1.2 (Mac/Win, $399)
Inside its stylized amp-head interface, IK Multimedia's Amplitube offers a selection of preamp simulations modeled from Fender, Vox, Marshall, and Mesa/Boogie tube classics, and two generic solid-state preamps (see Fig. 2). You also get four tube EQ models (two American and two British styles); four models of power amps (low- and high-power models of a solid-state and a tube amp); eight modeled vintage and modern speaker cabinets with two selectable mic types and two mic placements; modeled Fender tremolo and reverb; and a noise gate.

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FIG. 2: IK Multimedia''s Amplitube offers over 1,200 different combinations of preamp, EQ, and speaker configurations.

Amplitube's amp-simulation page provides six standard amplifier controls (Gain, EQ Low, EQ Mid, EQ High, Presence, and Volume), but if the amp modeled didn't contain one or more of those controls (Solid State Lead, for example, has no Mid EQ), the missing control (or controls) will be grayed out. IK Multimedia says that Amplitube's simulations allow over 1,260 possible combinations.

If you would prefer to call up an entire amp simulation rather than individual components, the amplifier and cabinet sections have Match switches that will link the EQ, amp, and speaker model to the preamp model you choose. It's not possible to access only the modeled speaker cabinets to use with an external amp, but you can bypass individual sections such as the stompbox section, the amp section, and the master-effects section.

Amplitube also offers models of five classic stompbox varieties, which are placed before the amp and speaker simulations in the signal chain. You get a wah — complete with a highly responsive auto-wah mode — delay, chorus, flanger, and overdrive. In addition, Amplitube offers a selection of three digital effects: 3-band parametric EQ, stereo multitap delay, and reverb. You cannot rearrange the order of the effects, and they cannot sync to the host application.

Some of the effects, such as parametric EQ, have legends around the dials, but most have no markings at all. That won't be a problem for guitar players, who are used to making adjustments by ear, but the lack of markings limits Amplitube's versatility for anyone used to making precise parameter adjustments.

IK Multimedia ships a broad selection of presets with Amplitube, covering most popular guitar amplifiers and guitar-effects configurations. Presets labeled VIP attempt to capture the signature sound of a number of famous guitarists, including Steve Vai and Jimi Hendrix. Additional presets are available for download at The presets will help you get started with Amplitube, but before long you'll want to explore what it can do on its own.

To my ear, the matched preamp-EQ-amp-speaker combinations often didn't sound like the amps they purported to simulate. For example, the Vintage Clean model (which is modeled from a Vox AC30) can't get distorted without a stompbox; a real cranked Vox can. I found that, in general, the clean amps thinned out the sound, although the Tube Clean preamp (based on a Fender Super Reverb) added some really nice warmth and harmonics with the Vintage Open 4510 cabinet (see Web Clip 2).

Some of the distorted sounds lose definition at higher Drive settings, and they don't clean up well (an observation that is mentioned in the manual). The real strength of Amplitube is in all the combinations possible; it's very easy to find groupings of preamps, amps, and speakers that can cover almost any sonic territory. Moreover, the stompboxes sound so good that Amplitube could stand alone as a great analog-style multi-effects plug-in.

A standalone version of Amplitube called Amplitube Live is available for the Mac, and, according to IK Multimedia, a Windows version will be available by the time you read this.

Pros Excellent stompbox effects. The auto wah is very dynamic. Over 1,200 model combinations possible. Presets cover Amplitube's capabilities well.

Cons No tempo sync for effects. Cannot rearrange stompboxes. Cannot use only speaker simulations. Many amp models thin or unconvincing.

Compatibility Mac OS 9: HDTM, RTAS, VST/OS X: HDTM, RTAS, VST, AU. Windows: RTAS, VST, Direct X.


Combo (Mac/Win, free)
MDA's freeware Combo plug-in (see Fig. 3) seems spartan compared with the other big-ticket simulators; it has no GUI, no presets, and a limited number of adjustable parameters. Perhaps because of its inauspicious appearance, I was surprised to find how much I liked it. Its simple architecture makes experimentation a snap. Its High Pass and Drive parameters are very responsive; small changes can make dramatic alterations in the sound.

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FIG. 3: MDA''s freeware Combo plug-in may not look like much, but its simplicity belies its sound quality.

Combo's six speaker simulations each have a very distinct personality and produce tones ranging from convincing amp sounds to transistor-radio effects. Indeed, I found that the High Pass control (which determines how much low end a tone contains) and the speaker simulator worked well in combination to create the basis for the sound that the Drive, Density, and Bias parameters would then shape.

My favorite speaker simulations were 4512 Edgy, which sounds very in-your-face and live; MB Distant, which sounds wonderfully full and amplike; and Transistor Radio, which allowed me to achieve some great special-effects guitar tones when used in tandem with the highpass filter. If you want to use only the speaker simulator in Combo, you can set the other controls to zero and they won't affect the sound, allowing you use it in conjunction with a real tube amp.

Combo doesn't disappoint in the distortion department, either: it can deliver unholy gobs of gain. If turned too high, the gain control can overload the signal. I found that the sweet spot on the gain control is between 35 and 75 percent, depending on the type of sound you're going for, from edge-of-breakup to gut-busting metal (see Web Clip 3). Combo's distortion doesn't sound tubelike; it's more like a solid-state transistor distortion. It's not quite liquid smooth, but not digitally buzzy either (unless you overload to digital clipping, of course). When you use a lower Drive setting, Combo reacts pretty well to playing dynamics. At higher gain levels, any dynamics in your performance are lost.

Combo doesn't sound like any specific vintage or modern guitar amp, and it doesn't claim to. Instead, it offers a CPU-friendly palette of tasty guitar-amp processing, and leaves it up to you to put together amplike sounds. Personally, I loved it for adding amp-style processing to dry guitars and for creating out-there, transistor radiolike, grunged-out tones.

Although Combo doesn't have the breadth of features that the commercially available amp modelers do, it's a wonderful addition to any plug-in library. Considering that it's free, and that it comes with a whole suite of free plug-ins, there's no reason not to download it and give it try.

Pros Free. Excellent range of tones possible. Speaker simulators can be used alone. Low CPU requirement.

Cons No GUI. No Presets. Controls can seem finicky. Doesn't simulate any specific amps. Limited dynamics at higher gain settings.

Compatibility Mac OS 9: VST/OS X: VST, AU. Windows: VST.


Native Instruments

Guitar Rig 1.12 (Mac/Win, $499)
With the release of Guitar Rig, Native Instruments has brought its reputation for quality synthesis to guitar modeling. The program, which runs as either a standalone application or a plug-in, has a two-paned interface with the left pane featuring parameters, presets, and guitar-rack components, and the right side housing the virtual guitar rack into which all the effects, amps, cabinets, and other goodies are placed (see Fig. 4). Unlike ReValver, Guitar Rig's components may be arranged in any order.

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FIG. 4: Native Instruments'' Guitar Rig contains nearly everything a guitarist could want, along with all the software features a computer recordist needs.

Guitar Rig offers not one, but two digital-recording components called Tape Decks. The first is a file player with variable pitch and tempo controls, which you can use as either a backing-track player or as a practice tool for slowing down guitar parts you are trying to learn. This deck also includes looping controls and the ability to play at input or output. The latter allows you to record the backing loop along with your guitar for even more creative options.

The second deck is designed for recording what you perform through Guitar Rig, although it too includes looping and file-playback capability. The Tape Decks are valuable not only for guitarists, but they lend Guitar Rig to experimental-effects uses as well.

Guitar Rig is one of the few simulators that has a tuner. You also get a metronome, a CPU meter; a noise gate; input-, master-, and preset-volume controls; and full MIDI learn capability (for MIDI software controllers and guitar-oriented MIDI footpedals). To complete the package, Guitar Rig comes with Rig Kontrol, an outboard pedal with four footswitches and an expression pedal — all fully programmable (see Fig. 5). The Rig Kontrol, which also functions as a preamp, enables a laptop-equipped guitarist to use Guitar Rig in place of an amp-and-effects setup for live performance.

Guitar Rig includes four amp models: ACbox (Vox AC30), Plexi (Marshall Plexi), Gratifier (Mesa/Boogie Dual Rectifier), and Twang Reverb (Fender Twin Reverb). Each amp simulation has a GUI resembling the original amplifier, complete with its relevant controls. The models also feature tweaky amplifier parameters such as Variac (AC level) and Sag (rectifier sag).

Guitar Rig's cabinet modeling offers extensive options. In addition to 14 cabinet models, you get 5 mic placements; 5 microphone models; a parameter called Air that adds room ambience; controls for pan, volume, bass EQ, treble EQ, and volume; and even a cabinet-size adjustment.

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FIG. 5: Guitar Rig is the only guitar-amp simulator to come with its own hardware controller, the Rig Kontrol.

A wide range of effects models is included, many derived from classic stompboxes and rack units. You get volume boosters, echo units, wah-wahs, chorus/flanger units, a talk wah, rotor units, octave dividers, EQs, tremolos, a noise gate, a tube compressor, and even a splitter to create parallel stereo tracks of effects. Indeed, you can create complex routings of amps and effects; your only obvious limitations are your own creativity and your CPU power. When Guitar Rig is used as a plug-in, all of the effects featuring tempo-based parameters can sync to the host's tempo.

Not only do you get a large amount of power and flexibility, but the models sound great. The Gratifier and Twang Reverb simulations are the best models of their type that I've heard (see Web Clip 4). As a former Twin owner, I was amazed at how well the Twang Reverb nailed the Fender tremolo sound. The ACBox amp sounds excellent, although its tremolo isn't as realistic as the Twang Reverb's. The Plexi is usable, but Marshall sounds are not Guitar Rig's main strength.

Overall, the models respond well to playing dynamics. Guitar Rig's effects are also high caliber. I couldn't get great results from Oktaver, but the other effects are convincing replicas of the devices they emulate and good effects processors in their own right.

Guitar Rig isn't cheap, and it's not without some flaws. For users who are serious about their guitar-amp simulator software, though, it's a compelling product.

Pros: Very flexible. Large variety of speaker simulations and effects. Good sound quality. Runs in standalone or plug-in mode. Includes recorder with variable pitch and variable tempo. MIDI learn capability. Tempo-based effects sync to host tempo. Huge library of presets. Rig Kontrol pedal.

Cons Pricey. No mono plug-in (only mono-stereo). Complex guitar racks eat a lot of CPU.

Compatibility Mac OS X: VST, AU, RTAS, standalone; Windows XP: DX, VST, RTAS, standalone.

Nomad Factory

Rock Amp Legends 1.0 (Mac/Win, $399)
Nomad Factory's Rock Amp Legends invokes the heyday of guitar rock. Former Aerosmith six-stringer Jimmy Crespo is credited with helping to develop the plug-in's sound, and the GUI is based on a classic Marshall amp (see Fig. 6). The plug-in offers three simulations of six classic styles of guitar tone: Classic Lead, a sort of Plexi-style Marshall tone; Modern Lead, a high-gain, modern Marshall sound; Combo, a stylized 1512 or 2512 sound reminiscent of Vox combo amps; Tweed, a vintage Fender tone; Super Lead, a '70s Marshall Super Lead; and Rectified Lead, which offers the high-gain crunch of a Mesa/Boogie Dual Rectifier.

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FIG. 6: Nomad Factory''s Rock Amp Legends looks like a classic British ''70s amp, and it sounds like one, too.

The interface offers a pull-down menu of amp-cabinet simulations, as well as standard amplifier controls. Clicking on the FX switch changes the GUI to reveal half-rack representations of various available effects: a stereo imager, a 3-band semiparametric EQ, a compressor, a noise gate, a delay, a modulator (chorus/phaser), and a tremolo. Finally, you get an A/B feature to load and compare two completely separate settings, and a choice of High or Low Input (featuring a cool graphic of a guitar plugged in to either input); the former adds a small boost to your signal.

Rock Amp Legends doesn't just look like a Marshall, it sounds like one. The Classic Lead and Modern Lead simulations are uniformly excellent. The sounds are full bodied, with that trademark midrange grit that rockers know and love (see Web Clip 5). The simulations are very sensitive to amp-parameter adjustments, so it's easy to get your own Marshall-like sound. These simulations respond well to playing dynamics, especially at moderate (>60) Drive settings.

Although the Marshall emulations are the standouts, the Combo and Tweed models are also quite usable. The Rectified Lead simulations sound a bit too scooped and nasal for my taste, but users who like that aspect of the Mesa/Boogie sound might love them. It's too bad that you can't access the amp and speaker simulations separately. I wish that I could have, for example, tried the Rectified Lead amp tone with a 2512 simulation, or turned the amp simulation off altogether to use the speaker simulations alone.

Rock Amp Legend's noise gate is excellent. It's adjustable, and it's effective in quieting noisy pickups and heavy distorted patches without adversely choking the tone. The tremolo is also excellent; it's deep and rich, and responds well to playing dynamics. The compressor colors the sound, but that's par for the course with guitar compressors. The rest of the effects are all usable, though not exceptional.

The GUI for the FX section offers little in the way of user feedback. Other than a miniscule on-off light, only the compressor and noise gate give you any metering. None of the effects have numeric readouts, only position dots around the dial. You have no control over the order of effects other than a switch on the compressor and noise gate to place them before or after the amplifier simulation. Finally, none of the effects can sync to the host tempo. At the time of this review, parameters in Rock Amp Legends responded to sequencer automation under all supported plug-in formats except for Audio Units.

Pros Great Marshall-style simulations. Excellent noise gate and tremolo. Responds well to playing dynamics.

Cons Limited ability to rearrange effect order. No host sync for effects. No AU automation. No way to separate amplifier and speaker simulations.

Compatibility Mac OS 9: VST, RTAS, HDTM/OS X: VST, AU, RTAS, HDTM. Windows: VST, RTAS, HDTM.

The Loud and the Software

Guitar-amp modeling software has gotten better and better. Some products are more successful than others at sounding like classic amps, but all definitively sound like amplifiers. Although none of five simulators were flawless, Native Instruments Guitar Rig offered the most complete package in terms of features and flexibility. Its Rig Kontrol pedal is a completely unique accessory. That said, Guitar Rig was the most expensive of the five products in this roundup, and not every user wants or needs that much amp simulator.

All of the plug-ins generally excelled in one area or more. If you want a great Marshall simulation, for example, Rock Amp Legends is a good choice. If you are on a budget, you can't beat Combo. If you are looking for an excellent Fender Twin, then Guitar Rig or Amplitube might be the ticket. Because most of the simulators offer additional goodies such as effects, tuners, and so on to sweeten the deal, you should definitely take those features into account as well.

Keep in mind that anyone's opinion of a given simulation depends on personal taste as much as algorithm quality. How faithful a simulation is to the amp it's modeling is not the only factor that determines its sound quality. You may prefer the modeled sound. Many guitarists, if you ask them privately and promise secrecy, will admit that they prefer their Line 6 Pod or Vetta over the real McCoy.

Even though the technology is better than ever, digital-amp simulations are unlikely to ever convince longtime tube snobs to sell their hardware. These plug-ins are good-some even great-but they're still not a complete replacement. There is something unique about the sound of a tube amp that software cannot yet completely capture.

But for many recording situations, it's hard to beat the variety, quality, and convenience of amp-modeling software. Guitar-amp simulation plug-ins are beginning to do for guitarists what software synthesizers have done for keyboardists — free them from the limitations of hardware, while offering them the sounds they love.

Orren Merton is the author of Logic Pro 7 Power (Muska & Lipman, 2004) and GarageBand Ignite! (Muska & Lipman, 2004).

Blending Real with Virtual

If your amp-modeling software allows you to use its speaker simulator independent of its other processing, you can take a line out from a real guitar amp into your audio interface, and record direct through the virtual speaker cabinet. You can use programs such as Guitar Rig, Combo, and Guitar Amp Pro (in Apple's Logic Pro) in this manner. It's the same concept that guitarists have been using for decades with speaker simulator hardware, such as products made by Palmer or Hughes & Kettner.

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FIG. A: If your amp has a line out, you can connect it directly to a line input on your audio interface. Remember that you''ll still need to hook your amp up to a speaker to avoid damaging the output transformer.

The setup is simple. If your guitar amp has a line out, plug it in to an instrument input on your audio interface (see Fig. A). If it doesn't have a line out, you can use the line out of a speaker-attenuator box such as the THD Electronics Hot Plate. Plug the attenuator into the speaker jack of your amplifier (using a speaker cable, of course), and then run an instrument cable from the attenuator's line out to your audio interface's instrument input (see Fig. B). Once you have your amplifier -connected to your computer, put a sequencer track into record, instantiate your guitar amp plug-in, and dial up your favorite speaker simulation.

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FIG. B: If your amp does not have a line out, you can still connect it to your audio interface with the help of a speaker attenuator such as the THD Hot Plate.

You can monitor your sound two ways. The first is to run your amp through both the computer and your speaker cabinet; your tone will be recorded from the line out, but you'll hear the room tone from your cabinet. The method I prefer, however, is to monitor completely through the computer; that lets me hear the exact tone I'm recording, at neighbor-friendly volumes. If you are not going to use the amp's speaker, though, it is important to know that you'll need a device (such as the THD Hot Plate) that can send out a dummy load to your amp; otherwise you can blow its output transformers.

To me, using a real amp and a speaker simulator is the best of both worlds: the convenience and range of the speaker and microphone simulations of the software, with the tone of a real cranked amp.

Amp Sims in Pro Tools

Three software developers currently offer amp-modeling plug-ins for Digidesign's Pro Tools TDM systems. Each has its own approach to the modeling process and provides different parameter controls, resulting in tonal characteristics unique to each. (Two of the three, Bomb Factory SansAmp PSA-1 and McDSP Chrome Tone, also run native. SansAmp PSA-1 also runs under RTAS and AudioSuite, and Chrome Tone under RTAS.)

Bomb Factory SansAmp PSA-1 (Mac/Win, $395) is a software emulation of the Tech-21 SansAmp PSA-1 and functions in much the same way. Overdrive is achieved in two separate stages: the Pre-Amp gain control simulates overdrive in the preamp stage, and the Drive knob controls power-amp distortion. In addition to Low and High tone controls, the output stage features a makeup level control.

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FIG.A: Bomb Factory SansAmp PSA-1.

All of the control knobs have an indent mark representing unity gain. The SansAmp PSA-1 also sports knobs marked Buzz, Punch, and Crunch, which control the amount of overdrive in the low, mid, and high frequencies respectively (see Fig. A). Different combinations of overdrive can yield a wide variety of sounds-from fat sustain to power shred (see Web Clip 1). The factory presets are useful, and the PSA-1 sounds great on other instruments as well. It uses relatively little DSP power.

Line 6 Amp Farm (Mac/Win, $595) bases its design on emulations of classic guitar amps (see Fig. B). It offers models ranging from vintage Fenders and Marshalls (see Web Clip 2) to modern Soldano and Mesa/Boogie amps. Each of the program's 13 amp heads is an accurate representation of the corresponding hardware version, complete with graphic representations of tone controls and switches specific to the selected make and model.

Amp Farm offers a range of speaker-cabinet simulations based on hardware models such as the Vox AC30 and Fender Deluxe, combined with several mic-placement options. Mixing and matching amp heads and cabinets can achieve a wide variety of tones. Whether used on input or as a mixdown effect, Amp Farm makes it easy to dial-in authentic-sounding guitar-amp tone.

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FIG. B: Line 6 Amp Farm.

McDSP Chrome Tone (Mac, $495) is a suite of plug-ins providing amp simulations and effects. The amplifier module is extremely flexible, featuring six preset levels of distortion combined with compression, gating, and EQ (see Fig. C). The distortion section has an Amount control coupled with single-band (200 Hz to 2 kHz) Frequency and Drive controls to tune the overdrive tone, followed by an output level control. The compressor offers threshold, response (attack), sustain, and release controls.

In addition to a noise gate, you get a 3-band parametric equalizer for further tone sculpting. The output stage includes a spring reverb, a level control, and four speaker simulations.

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FIG. C: McDSP Chrome Tone''s Amp module.

Chrome Tone's amp module is formidable as a standalone simulator, but it can also run in Stack mode with other included effects such as wah (see Web Clip 3), tremolo, tape echo, and chorus. The depth and modulation of these effects can be triggered by a range of input types (sidechain-audio input, MIDI notes, and so on), making the application very flexible and musical.

Chrome Tone currently runs only on Mac Pro Tools systems, but McDSP says that a Windows version should be available by the time you read this. In addition, a version called Chrome Tone Amp is available as a plug-in for the VS8F-3 plug-in expansion board for Roland VS recorders. -David Darlington

Accelerated Amps

In addition to the native and TDM guitar-amp simulations available, two DSP plug-in accelerator packages, the TC Electronic PowerCore and the Universal Audio UAD-1, also offer guitar-amp simulation software. Since the plug-ins require hardware in addition to your computer to run, they're not technically native and therefore don't fit the criteria for this roundup. However, they're close enough that they do deserve mention.

PowerCore and UAD-1 plug-ins are compatible with the VST format on Windows and Macintosh computers and AU in OS X. Universal Audio offers the guitar-amp plug-in Nigel free with any UAD-1 package. TC Electronic includes one of its amp simulators, Tubifex, with all PowerCore packages, and the TC Thirty amp simulator plug-in is sold as an option.

At first glance, hardware DSP accelerators might not seem conducive to amplifier simulation because they double a system's latency, at best. But the appeal of DSP accelerators has always been that taking the process off the CPU allows for more processor-intensive algorithms, and that quality advantage applies to guitar-amp processing. The TC PowerCore plug-ins all feature a no-latency mode which, at the expense of CPU, runs the PowerCore process in parallel to the CPU buffer, eliminating the latency.

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FIG. A: TC Electronic''s Tubifex plug-in runs on the company''s PowerCore system.

So how do they sound? Universal Audio's UAD-1 card has a well-earned reputation for truly spectacular analog processor emulations. Although Nigel is a nice addition to the package, it's not the equal of some of the other UAD-1 processors, nor does it stand above the native amp modelers. Its strongest point is its filter and modulation effects, which allow for some cool processed amp sounds. Because of the latency inherent in the UAD-1 system, it's only useful as a mixdown effect.

TC Electronic's Tubifex has a simulation of, among others, the Marshall Super Lead (see Fig. A). Its Expert level allows for almost ludicrous amounts of fine-tuning. The TC Thirty plug-in does an admirable job of capturing a ‘60s non-top-boosted Vox AC30 with the addition of a Treble Booster circuit (as made famous by Brian May).

Apples and Apples

When Apple Computer unveiled GarageBand as part of iLife ‘04, one of its key features was Amp Simulation, a built-in guitar-amplifier simulator specially designed for it. It was no surprise that when Apple announced Logic Pro 7, it featured a souped-up and expanded guitar-amp simulator called Guitar Amp Pro. The simulations are accessible only from within those two host applications, but they are definitely noteworthy.

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FIG A: Guitar Amp Pro, included in Apple''s Logic Pro 7, stands up against the commercial offerings mentioned in this article. Its engine also powers GarageBand''s Amp Simulation.

Amp Simulation and Guitar Amp Pro are well imagined for their intended audience. Amp Simulation effect has the same look as the rest of GarageBand's effects. Intended to be simple and intuitive for musical novices, it comes with eight presets that cover the basics of the four modeled amplifiers (one each from Vox, Marshall, Mesa/Boogie, and Fender).

GarageBand has no speaker-simulator selection; each amplifier simulation is internally paired with its matched cabinet. Besides radio buttons to select from the four modeled amps, you have a basic selection of common amplifier controls — Pre-gain, Low, Mid, High, Presence, and Master.

Although it doesn't have as extensive a feature list as most of the commercial amp-modeling plug-ins, Amp Simulation's models are full sounding, and its clean tones are particular standouts. The simulations respond well to playing dynamics.

Guitar Amp Pro, in addition to having a sleeker interface (Fig. A), more than doubles the number of amplifier models and triples the number of cabinet simulations in GarageBand, while also offering all of Amp Simulator's models. Although it doesn't have a specific bypass setting for its EQ and preamp sections, a workaround (selecting the Clean Tube Amp model and the Modern EQ at their default settings) effectively turns off those sections, allowing you to access the speaker simulations by themselves.

You can mix and match amp, EQ, and speakers at will, or click the link buttons to call up entire combinations as originally modeled. Guitar Amp Pro's set of basic controls is similar to its GarageBand counterpart's, and the models are very responsive to minute adjustments. You can select from two microphone types and two mic positions, and Guitar Amp Pro offers an excellently modeled tremolo, vibrato, and spring reverb. That may not seem like very many effects, but keep in mind that you have Logic Pro's entire suite of acclaimed plug-ins along with it.

Logic Pro 7 takes advantage of its new ability to load and save channel strips by including channel strips that feature Guitar Amp Pro along with other Logic effects. Guitar Amp Pro itself comes with a healthy number of presets that show off its range of amp sounds. It sounds particularly authentic in its American Clean tones and in the American and British edge-of-breakup tones (see Web Clip D). When the gain channels are pushed to their limit, however, the sound is a bit more compressed than I'd prefer. All the speaker cabinet simulations are quite convincing, and the tremolo, vibrato, and spring reverbs are definite standouts.