I stumbled across this thread by accident. didn't know there was a way to get dacs work with the iphone! I'd like to try it with my iPhone 4, a Fiio e07k and my B&W P7. Do I need any additional cable? From what I have read there is an USB to micro USB included with the Fiio, so I wouldn't need anything else. Is this right?
As far as cables, you will need iphone 4 > 30pin to 3.5mm > Fiio (analog in) OR iphone 4 > apple 30pin camera connect kit > usb to usb mini > Fiio (digital in). Im not sure if the second configuration will work or even be beneficial because as far as I know, 30pin outputs are all analog. I also don't know if you will get the "this usb device draws too much power" error in which case you'd have to add a powered usb hub into the chain after the CCK, which will make the setup become non-portable. The first setup is your typical iphone to portable amp setup and utilizes the iphone's internal dac (which cannot be bypassed via 30 pin) and the Fiio's amp section...but im sure u knew that already :)
The 2nd configuration mentioned by MeowMix is the one to go with so you bypass the DAC in your iPhone. The cable you need to add is the CCK - camera connection kit. The 30 pin CCK includes two adapters - one USB and one SD card. You only use the USB one.
iPhone4 -> Apple 30 pin CCK -> USB to USB mini -> Fiio e07k USB input -> B&W P7 headphones
As mentioned, just make sure to turn off USB charging on the e07k or else you'll get the 'too much power' error. This setup will send digital audio to the e07k USB input and the e07k will do the DAC (digital to analog) conversion and then amplify the analog signal to feed the headphone output.
And as mentioned above by teb1013, your iPhone 4 needs to have iOS 7.x loaded.
Edited by AgentXXL - 11/28/13 at 8:12pm