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BootlegMIC with iPhone 5 - How Should I Start Tweaking?

PostPosted: Mon Nov 05, 2012 6:24 pm
by tcbrekke
Hi all,

Built a few bootlegMICs from kits, not much of an tinkerer but this looked like too good a project to pass up. Needless to say, now I'm looking for more things to do with my soldering iron. The following will be one such thing, but I need a little help figuring out where to begin.

I've built three bootlegMICs, and all three work with the iPhone 4 and 4S. I recently purchased an iPhone 5, and it doesn't quite work with the iPhone 5. The resulting recordings sound as if there's massive interference of some kind up until there's enough signal coming from the mic to cut through the noise. Then, it's nice and clear. Until the signal goes away. Then interference-y whine again.

I've looked at the schematic of the mic on the wiki, and it makes enough sense - now I'm guessing that there's some incompatibility between the drain resistor inside the phone and the gain of the mic itself, but from there I'm not sure how to begin experimenting to figure out where the iPhone 5 needs it. Any tips from a more experience maker who might be able to give me Point A so I've got somewhere to start from on my quest to Point B?

Thanks in advance, and thanks for making these plans and kits available!

Re: BootlegMIC with iPhone 5 - How Should I Start Tweaking?

PostPosted: Mon Nov 05, 2012 7:21 pm
by guest
there are 2 possible sources for the problem that i can think of. the first is that the iphone is expecting a slightly different impedance. you can try soldering a 10k resistor across the 22uF capacitor. if that doesnt work, try a 2.2k resistor and see what happens. basically, the internal circuit tries to detect whats connected to it. if the impedance isnt right, then it doesnt think its a microphone.

the other thing is the automatic gain control inside the phone. im not sure what to do if thats the case, but maybe listening to sound samples would give me some ideas.

let us know how it goes!

Re: BootlegMIC with iPhone 5 - How Should I Start Tweaking?

PostPosted: Tue Nov 13, 2012 11:52 am
by tcbrekke
Hi, sorry about the period of time between posts. I have not yet had a chance to try this out, the last weekend got real busy real fast, but I've got a Friday to myself this week and will be picking up a small handful of resistors and warming up the soldering iron again to try out your suggestions below. Next I will also try and get some recordings of the current state of the microphone on SoundCloud in the next 24 hours. Thanks so much for your suggestions, can't wait to get to fiddling with this!

Re: BootlegMIC with iPhone 5 - How Should I Start Tweaking?

PostPosted: Sun Jul 27, 2014 12:05 pm
by Yetzederixx
This playlist on my company YouTube channel were all done with a iPhone 5. Much of the zoning in and out was due to a wonky PA system though. Going to test it out again at another show later in August.