The iPad is the perfect practice tool for guitarists. Because it instantly becomes whichever app you load, it can be a warehouse full of amps, a fully-featured demo studio, a TAB reader and writer, a guitar synth, a scale library, and probably a whole bunch of other thing we haven’t even envisioned yet. But most of these functions are useless with a guitar signal entering the iPad. There are plenty of interfaces for guitar out there, and they all seem to operate in different ways. Some are simple and inexpensive, while others are a bit more pro-spec. That’s where the GuitarJack Model 2 comes in.

GuitarJack Model 2 is an interface for iPad, iPhone and iPod Touch, and it’s made of rugged aluminium steel. Unlike many other such devices, this one really feels like a pro piece of gear. Pick it up and there’s a decent amount of weight to it. It has the standard 30-pin dock connector; a 1/4 nickel-plated solid brass Switchcraft (10,000 MTBF) jack; 1/8 inch stereo mic/line input (no phantom power is provided); and a 1/8 inch stereo headphone/line output with increased drive for headphones. It’s powered by your iOS device, so you don’t need to keep feeding it with batteries; and at its heart is a 24-bit AD/DA converter. Currently it operates at 16-bit audio playback and recording, but a firmware upgrade in the future will unlock the full 24-bit potential.

GuitarJack Model 2 supports any CoreAudio app, and there are dedicated GuitarJack settings in various apps – GuitarTone, FourTrack, StudioTrack and Taylor EQ – which give you access to 60dB of continuous level control, Pad, Lo-Z (low impedance) and Hi-Z modes for the instrument input; mono, dual-mono, stereo, Pad, Normal and Boost modes for the Mic/Line in; and Mic/Line input on the right channel and Instrument on the left channel for both inputs.

GuitarJack Model 2’s sound quality is the highest of any iOS interface I’ve used. Some others come close, but GuitarJack 2 has them pipped in terms of physical strength and input option flexibility. It also has an advantage over some others because many models either require that you use a cable with a 1/8″ jack on one end, or they have their own cable hardwired as part of the assembly. For testing I plugged my guitar into a Radial A/B box, loaded up my favourite AmpKit preset on both my iPad and iPhone, sent each to my mixer and used the Radial to switch between other interfaces (IK Multimedia iRig and Line 6 Mobile In). GuitarJack 2 stood out in sheer dynamic range and low noise, and it seemed especially lively in the high ends, whereas many interfaces seem to dull this down. It helps to add extra realism to amp sim apps, and it provides a nice clean signal to tuner apps, which is very handy for those of us who like to whip out the iPhone to intonate our axes when a physical tuner isn’t around.

A caveat: the weighty robustness of GuitarJack Model 2 means it’s a bit too heavy to stay in the iPad if you stand it up using the SmartCover, so it’s advisable to purchase a dock extender cable as well. This isn’t quite as necessary for iPhone or iPod Touch but it still helps, so I would definitely recommend taking this step in order to get the most out of the GuitarJack 2. Other 30-pin dock connector interfaces may be lighter and not as prone to this problem, but it’s a side-effect of the rock-solid construction so I wouldn’t consider it to be a flaw.

If the only thing GuitarJack Model 2 did was to provide a great low-noise guitar interface in a high quality casing, it’d be a no-brainer. The fact that it also includes the Mic/Line input and that you can use both at once in various apps makes it an indispensable tool for the guitarist on the go.