Many of us have iPhones, some of us have iPads, and it can’t have escaped your attention that there are many apps available for iOS devices aimed at guitarists.

From the simplest tuner, to tab and tutorial apps, through amp simulations and multitrack recording suites, there’s plenty for players at all levels – and often at real pocket money prices. To take advantage of some of these, though, you need to plug in a guitar, and there are several devices on the market that let you do just that. Of course, you could always grab a Squier USB Strat from the Apple Store and do without an interface, but that's not the only option.

What’s often needed is a piece of hardware that will take the signal from a standard guitar jack lead and get that signal into the iOS device. It can do this in one of two ways – either through the mini jack headphone socket or through the dock (a 30-pin connector).

Obviously if you’re using the headphone socket you can’t use it for headphones, so any input devices that take this route provide their own inbuilt headphone socket to compensate. A device that’s plugged into the dock has no such restriction, so you can still use the headphone socket for monitoring.

Some input devices are essentially adaptors that route the analogue signal in and let the iOS device’s own A/D converters do the rest while others can send a digital signal in. We give you the lowdown on six different input devices to help you decide which is best for you, although the imminent arrival of Line 6's Mobile In is likely to increase the competition even further.

Bear in mind that while most apps should be compatible with any input device, there are some exceptions – for example, at present IK Multimedia’s AmpliTube will only accept an input through the iPad’s headphone socket.