Since the mid-1990s, modeling technology—the digital simulation of musical sounds—has given guitarists access to increasingly lifelike effects and amp replications in progressively smaller packages. And while modeling technology has for years figured into computer software programs, it now makes possible the applications that allow musicians to turn their cell phones into stompboxes, amplifiers, and even recording studios. We checked out two such exciting apps, the Peavey/Agile Partners AmpKit and IK Multimedia’s AmpliTube 2, and their associated (and interchangeable) interfaces, the LiNK and the iRig.

Peavey AmpKit LiNK
Peavey’s pocket-sized AmpKit LiNK ($29.99 street) is a high-fidelity interface whose 1/4-inch input will accept a guitar, bass, or other electric instrument (see Fig. 1). The LiNK’s built-in 1/8-inch stereo-output cable links the unit with the headset jack of an iPhone, iPod touch (excluding the first-generation version), or iPad; an 1/8-inch stereo jack allows you to plug headphones into the LiNK or send the output to powered speakers.

The LiNK is designed to work with any iOS application that uses audio input, particularly Agile Partners’ AmpKit, which is available as a free download at the iTunes store. This app includes simulations of Peavey’s ValveKing amp with clean and ultra-high-gain lead channels; 4x12 and 1x12 cabinets; two pedals, the Noise Gate and the Elevenizer, a tone shaper; and two microphones, the Workhorse 57 dynamic (modeled on a Shure SM57) and the Germann 87 condenser mic (patterned on the classic Neumann model). It’s also loaded with some handy accessories—a built-in tuner, a metronome, and a recorder.

FIG. 1: The Peavy LiNK.

AmpKit has a number of extra amps and pedals that you can buy directly through the app. These include, among others, the Peavey 3120 ($5.99), The Vintage Brit (like a Vox AC30, $4.99), and the Colonel Vintage (Marshall JTM45, $4.99) amps; and the 10-band EQ Monster ($4.99), the Juicer compressor ($2.99), Distortoise ($2.99), the Haze fuzz ($2.99), Echology reverb ($4.99), Ensembly chorus ($2.99), the Lone Flanger ($2.99), and Phunk Phaser ($2.99) pedals. All of these sounds are also bundled into the AmpKit+ app, which costs $19.99. In addition, the AmpKit store offers six other mic simulations, each costing $0.99, from the Workhorse 58 (modeling a Shure SM58) to the KGB 451 (an AKG 451 model).

In preparation for testing AmpKit+, I downloaded the application on an iPhone 4 using a Wi-Fi connection. I then removed the AmpKit LiNK from its packaging and installed the included pair of AAA batteries, said to cancel feedback, which required a bit of struggling with the less-than-optimally designed compartment door. (According to the LiNK literature, the powered circuitry "substantially reduces feedback when headphones are used. This differentiating feature should be part of any evaluation of AmpKit LiNK versus non-powered guitar interfaces, particularly with high-gain setups." In other words, the batteries power a circuit that minimizes feedback. During the fact check, a company representative told us that “because it has a built-in headphone amp, the LiNK greatly reduces the current flow in the cable that connects to the iPhone, reducing crosstalk with the incoming signal from the guitar, and therefore reducing feedback dramatically.”)

From there, though, things couldn’t have been any easier. I plugged the LiNK into the iPhone, and connected a recent Gibson Custom 1963 ES-335 Historic and a pair of Grado RS-1 headphones (with an 1/8-inch adapter) into the LiNK, and things were all set up in a matter of moments.

AmpKit+ includes more than two dozen presets, grouped by genre and with various configurations of amps and effects that you can modify at your whim. I first engaged the most basic present, the King of Cleans—a 4x12 ValveKing with no effects, miked with a Germann 87. While the app was understandably not as satisfyingly responsive as an actual tube amp, the sound was quite good—warmish and round. I was able to get a nice range of tonal colors through toying with the amp’s presence, resonance, texture, bass, mid, and treble controls, not to mention its bright switch, all enhanced by the amp’s fairly lush and natural-sounding reverb. It was easy to further manipulate the sound by changing the microphone placement from on- to off-axis, swapping out the 4x12 cabinet for a 1x12, and switching to the lead channel, with its thick, smooth overdrive.

Next I put the ES-335 in drop-D tuning and tried the Nu Metal ValveKing, a heavily distorted preset with the Noise Gate and Elevenizer effects. The sound was as brutal as would be expected, but each time I stopped playing, if the strings weren’t muted I encountered some unwanted shrieking feedback—an effect minimized, though not completely negated, by fidgeting around with the volume levels both on the app and the iPhone. (The developer notes that it has addressed this problem in a recent software upgrade.) Other dirty tones, from slightly gritty to way overdriven, all sounded excellent, especially the “Metal on a Mountain Top” preset, with its dramatically cutting echoes, a product of the Echology effect.

On the main menu of each preset or user-defined setting is a recorder, which is intuitive to use with its one-button control. Each new recording is saved as a pair of WAV files in a library—one file is dry (unprocessed), the other fully processed. The developer notes that this lets you do “non-destructive re-amping.”

The recorder has decent sound quality and allows any file to be sent wirelessly or via email to a computer. Here’s another cool feature: It’s possible to upload any dry guitar recording as a WAV file from a computer and re-amp it in the AmpKit app.

The app comes with a library of backing tracks, giving you something to play along with right away. If the styles and textures of the backing tracks are too generic for your tastes, simply send your own accompaniments to the library via Wi-Fi.

IK Multimedia AmpliTube 2 and iRig
From IK Multimedia, known for its desktop amp modeling software, comes AmpliTube iRig ($29.99 street). This interface is roughly the size of a guitar slide and works much like the AmpKit LiNK, except it is passive and, therefore, doesn’t require batteries (see Fig. 2). The iRig is intended for use with the free AmpliTube 2 app, whose clever display is set up like a pedalboard. The app comes with three stompboxes—delay, noise filter, and distortion (free with registration). It also has a 4x12 head-and-cab amp with distortion and reverb; two mics, a dynamic and a condenser; a recorder; a chromatic tuner, visible at the bottom of most screens; and a metronome, settable either in the conventional manner or to a tapped tempo (see Fig. 3).

The AmpliTube 2 app is also available in a couple of enhanced versions. The LE version ($2.99) adds two stompboxes, chorus and wah; a deluxe edition ($19.99) has 11 stompboxes—those included with the LE, plus overdrive, flanger, octave, envelope filter, phaser, and fuzz—and a total of five different amp and five different cabinet configurations.

FIG. 2: IK Multimedia iRig

I tried the deluxe AmpliTube 2 app, again using an ES-335 and Grado headphones. As with the AmpKit, it was a cinch to get up and running on AmpliTube 2. With icons for the stompboxes, amp, recording, and mastering features all aligned atop the same screen, the layout of AmpliTube was a bit more convenient than that of the AmpKit. But controlling the pedals was a little counterintuitive. While each one was displayed as an old-fashioned stompbox that could be turned on or off by pressing its silver button, the dials couldn’t be turned; instead they had to be adjusted via a yellow meter to the right of each pedal.

When I first plugged into the iRig, I noticed a slight lag in time between the playing of a note and its emergence from the headphones. However, this was corrected easily enough by accessing the app’s Settings menu and putting the latency on ultra low. Another handy feature was an auto-sleep function, which saves the iPhone’s battery during long sessions with the amp. This mode can potentially cause clicks and pops, but playing around with the app for a few hours, I didn’t hear any.

The Settings menu also had a control for eliminating feedback, which proved true when I checked out AmpliTube’s distorted sounds. All were decent, albeit minimally differentiated. With the overdrive pedal, it was easy to get a crunchy classic rock sound in the mold of Keith Richards, and the distortion box provided a nicely singing quality for some jazz-rock soloing. As for the clean sounds, they really shone, especially when played with the delay and chorus stompboxes, affording many gorgeous and evocative sounds.

AmpliTube 2’s recording features surpass those of AmpKit. On the basic version, standard to all three levels of the app, a single track can be recorded in stereo or mono. But with the unit’s track bouncing functionality, a great number of overdubs are possible. The recorder also features mastering controls—reverb, with decay, color, and output parameters; a three-band EQ; and a compressor, with level and output knobs. Not only that, for just $9.99, the recorder can be upgraded to a four-track, making it a great deal more flexible.

FIG. 3: They play well with an iPad, too.

AmpliTube 2 also allows you to re-amp a recorded sound file, and easily export and import recordings through Wi-Fi or email. (It emails files as an MP3, but exports them as a WAV file.) In addition, AmpliTube 2 offers a great learning feature that is lacking in AmpKit: IK Multimedia’s SpeedTrainer lets you play an imported audio file at anywhere from half to twice the speed without affecting the pitch—perfect for learning a blistering solo. SpeedTrainer supports MP3, WAV, AIFF, and WMA file formats.

The Bottom Line
It goes without saying that the AmpKit LiNK and the AmpliTube iRig aren’t designed to replace a floor full of boutique stompboxes or a wall of tube amplifiers. And even though the latter has an optional four-track recorder, you probably wouldn’t use it to record your masterpiece. But each app offers seemingly limitless sonic possibilities and would serve as an excellent practice amp and scratch pad for a working pro, a learning tool for a less experienced guitarist, and a handy multipurpose tool for the home recording enthusiast.

Another great thing: You can use the same interface to connect with either app, and get the fully loaded versions of both, plus the optional four-track on AmpliTube 2, for a total of only $70—a fraction of the cost of a typical single-effect boutique pedal.

AmpKit LiNK System
Pros: Very good amp simulations and luscious time-based effects. Built-in tuner. Metronome. Recorder. Easy of use.

Cons: Interface housing not particularly sturdy. Recorder is simplistic and lacks mastering functions.

AmpiTube iRig System
Pros: Great stompbox effects. Built-in tuner. Metronome. One-track recorder (optional four-track) with bouncing and mastering controls. Ability to slow down or speed up prerecorded music without changing the pitch.

Cons: Distortion and amp simulations not as inspiring as the time-based effects. Pedals would be easier to use with fully functional virtual knobs.

Adam Perlmutter is a New York City-based guitarist/transcriber/arranger/music writer. He contributes articles to Acoustic Guitar, Guitar Aficionado, Premier Guitar, and other magazines. He is the author of several Hal Leonard guitar method books including Jim Hall Signature Licks.