Guitar effects processing software is nothing new. Effects processing software for the iPhone—which puts advanced effects processing power in your pocket—is a new phenomenon, however. Currently, there are two players: IK Multimedia, makers of the popular AmpliTube simulation software for Mac and PC, and indie developer Agile Partners, in partnership with Peavey.

Both companies make apps that use a combination of hardware and software to capture audio signals from a guitar and process them to produce a wide range of sounds, including amp simulation, distortion, and other effects. But which should you get? Read on to find out.

Hardware

You might expect the best way to get audio onto an iPhone would be through the dock connector, but both companies use the 1/8-inch headphone jack instead. Their respective devices work primarily the same way: instead of connecting a guitar to an amplifier, the 1/4-inch cable plugs into the units. Each device has a tail (the AmpLiNK cable is a good deal longer than the iLink) that plugs into an iPhone, iPod touch (second-generation or later), or iPad's headphone jack. Lastly, a pair of headphones needs to be plugged into the 1/8-inch jack on either device. Headphones are necessary, as neither application will output sound through the speaker while the headphone jack is occupied.

Neither unit feels particularly rugged, but the Peavey unit looks and feels significantly cheaper than than its competitor. The only major difference, aside from build quality, is that the Peavey unit takes two AA batteries, which power a small headphone amp. The amp does affect the device's performance, which we will get to later in the showdown. Each piece of hardware retails for $39.99, a price that does not include the cost of software.

Software

Each application involves four primary parts of the effects processing chain: the effects themselves, amplifiers, speaker cabinets, and microphones. A slight alteration to any of the four could lead to either a subtle or drastic change to the final sound. AmpliTube and AmpKit both offer free versions, which come with a minimum number of options and a number of à la carte equipment available for in-app purchase. Pieces of equipment range in cost from $0.99 to $6.99. The two applications also have $19.99 versions. IK Multimedia calls this version AmpliTube, while Agile Partners call its version AmpKit+. Additionally, IK Multimedia sells AmpliTube LE, which costs $2.99 and offers a small sampling above and beyond AmpliTube Free.

The vast majority of users will likely want to purchase the $19.99 version of both pieces of software. Buying the $19.99 packages makes more financial sense, even if there are one or two effects that aren't your cup of tea (we created the chart below to illustrate what comes in the free and $19.99 versions). The full version of AmpliTube includes everything the application has to offer as far as effects are concerned. AmpKit's $19.99 version, however, has additional pieces available for purchase; all told, you could spend as much as $97.49 more to buy all the available effects options.

In AmpliTube, items are named rather generically, while the AmpKit "gear" comes with more creative names. Whichever method you prefer, however, in many cases you'll have to remember that the name typically refers to some well-known piece of equipment that can't be named for trademark reasons.

For instance, the "Elevenizer" effect in AmpKit is modeled after the classic Ibanez Tube Screamer distortion pedal. The in-app purchase section of AmpKit tells the user what most of the gear is modeled after, which makes things easier, especially those familiar with that hardware.

Although AmpliTube doesn't come out and say it, it's fairly obvious that some of their equipment is modeled in a similar way. For instance, in AmpliTube, "Fuzz" also appears to be a Tube Screamer—as in AmpKit, the image of the pedal is the same signature shade of green that one would associate with the Ibanez unit. AmpKit is the only application of the two that has any brand-name gear at all, thanks to the partnership with Peavey.

Presets

Both apps offer ways to save and access presets, but they do so in different ways. Each has its advantages in certain situations, but neither is perfect. Upon first use, AmpliTube's way of representing presets is terrible, as each preset is represented by a number and nothing else. The numbers are laid out on a grid, and if you have a great memory the system makes it easier to switch between effects, as the need for scrolling is minimal.

AmpKit's preset functionality is more user friendly. Each preset can be named, and there are small images of each piece of kit displayed under the name. It isn't as easy to switch between presets due to the need to scroll, but finding the one you want is generally much easier by comparison.

AmpliTube on the left, AmpKit on the right.

While both applications come with some presets already preprogrammed, AmpKit's are locked. You can copy the original and then edit, but you can't delete the original. AmpliTube's custom presets are unlabeled and, compared to AmpKit, somewhat disappointing. We'll call this one a toss-up.