Building an iDevice Guitar Interface Cable

Amplitube on the iPad 2A few months back, I purchased the ultimate unnecessary-but-awesome gadget: the iPad 2.

With the availability of apps like Amplitube, AmpKit, and Garage Band, it’s immediately obvious how this device can be an amazing guitar learning and practicing tool.  I’ll talk more about that in another article.   But before you can plug in your guitar, you need a special interface…

Before we talk about building our own device, let’s consider the alternative.  There are a number of commercial interface products available.  The less expensive ones plug in through the headphone/microphone jack like IK Multimedia Amplitube iRigPeavey AmpKit LinkGriffin GuitarConnect.  That’s the type of device we’ll be building.  Then there are also the higher quality, more expensive products that have their own A/D converters and plug in using the dock connector- like Apogee JamSonoma GuitarJackAlesis iO Dock, Line 6 Mobile In and IK Multimedia iRig HD.

In part 1 of this 3-part video series, I introduce the project- how to make your own impedance matching, buffered guitar interface for the Apple iPad, iPod touch and iPhone.   These iDevices all share a similar headphone/microphone jack specification, so this circuit should work with all of them.

I’ll show you why a simple unbuffered cable interconnect will sound terrible- because of the significant impedance mismatch between a passive guitar circuit and the iDevice mic jack.  Also, the iDevice provides a 2.8V DC on the mic input to drive a microphone preamp, and as you’ll hear, this voltage totally screws up your guitar circuit.

This isn’t intended to be an ultra-high-fidelity interface. But trust me, it sounds good and costs very little. And the principals learned in this simple electronics project are the same as those required to make a guitar boost pedal like the Fulltone Fatboost.

In part 2 and part 3, I’ll explain all the electronics and show you how to assemble the interface.

Here’s some of the things you’ll need:

A 4 conductor cable, like these.  Note the tip-ring-ring-sleeve connector:

4 conductor TRRS cable 4 conductor TRRS cable - like an iBook audio/video cable Tip ring ring sleeve connector

Also, a female 3.5mm phone jack for your headphones, and a 1/4” female jack for your guitar:

3.5mm female phone jack for headphones 1/4" female phone jack for the guitar

I’ll cover the electronics components in part 2.