Tuesday, August 5, 2014

DIY iRig Guitar to iPhone Interface

I've just finished a project I started months ago.  Here's a working layout for the IK iRig version 1 for iPhone or iPad.  I am going to use my iphone as a strobe tuner for guitar and bass setups, and for recording demo songs on trips and such.  The main advantage of me building this rather than buying it, is my construction is a lot more robust than the plastic IK unit, and I used switchcraft jacks, star quad cable, etc.  Between this, and my two Tascam iPhone interfaces (line input, and stereo XY mic) I'm covered for portable audio.  Amazing.

In use, with IK's free Fender and Marshall Amplitube apps, there is noticeable latency when playing guitar, but it's tolerable.  Also, this iRig circuit is pretty noisy, and the output is pretty low.  Thankfully IK includes a noise filter as one of the selectable effects in the Marshall app.  The sound quality of Amplitube is harsh and gritty, but, it'll do fine for jamming, writing, or demo recording.  I would not use it for critical recording.

Here is some technical information:

http://www.danacsimmons.com/content/working-iphone-audio-input

And here's the schematic, my stripboard layout, and my finished unit.










8 comments:

  1. Hi. I didn't know how else to reach you. I wanted to ask you about comment you made in 2010 on the Tagboard Effects forum regarding the DAM Meathead. You suggested subbing in a 2n5306 to make it really dark - welll I did that but no sound came out. Is there a special configuration? Sorry for the random trackdown for an unrelated question on this blog but I really want to make this happen and it doesn't seem to want to. Thanks a million. :S

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    1. PS - it works completely fine otherwise.

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    2. Hi N8. Sorry I have not logged on to the stombox forums in quite some time!

      If you are substituting transistors in a given layout, the rule of thumb is to always double and triple check the pinout, as they are all over the place with different models. You want the Base, Ground, and Collector all to reach the correct pads for the circuit. You may have to bend the legs around in a funny way to get it right. If you google datasheets for your transistors you should be able to find the pinouts.

      Also you would always replace an NPN transistor with an NPN, a PNP with a PNP they are not interchangeable. Also BJT, JFET, and FET transistors all have their own rules and are not specifically interchangeable.

      If I remember correctly that transistor should be compatible with the Meathead you just need to get the pinout right.

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  2. Replies
    1. Hi, you will probably want to check your work very carefully for shorts, bad soldering, and wire and component routing, as those are typical problems that can keep something from firing up. Troubleshooting is just as much an essential skill as building. I find myself having to do it constantly, unless I work very slowly and methodically. Don't lose hope! The schematic and my stripboard layout are both verified so you should be able to compare your work to these images and hopefully find what might be not quite right about it. The first places I would probably check would be the pinout on the cables and jacks, and to make sure all the components are connected as per the schematic. It's pretty easy to goof that stuff up and not notice it.

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  3. Hello, i s there an option to control gain?

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    1. Maybe if you're smarter than me you could figure out the biasing of the FET and change one of the resistors to a trim pot. If you simply need attenuation you could add a "low" input copied off a guitar amp schematic, or an input trim pot of say, 100K or more.

      My best advice with my knowledge is to either use your guitar's volume knob for attenuation, a boost pedal for more gain,

      Or buy a Tascam iXJ2 which has gain controls for each of its two inputs, that sounds great with guitars. You would just use a 1/4" to 1/8" cable or adapter to get the guitar into the iXJ2. I don't know what they go for now but mine was very affordable. I use all of these products with my iPhone 4S and the apps Spire, Tascam PCM Recorder, with a variety of input sources, various instruments, and the Tascam iM2 for microphone recording. The sound quality is surprisingly good, frankly it blows my mind, so good for demo recordings on the go, or sampling, or concert bootlegs.

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  4. Really nice project dude. Thanks for sharing it !
    Would like to give this a go .

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