I think when the Explorer came out, it was found to be possible to use it with iPhone/iPad using a Camera Kit connector, and a powered USB hub. Googling the forum will find you details on that. I bought the Camera Kit connector to try it out but never actually got around to it. Anyway it's hardly an elegant solution.

If you want good sound while walking around, best off getting an Astell&Kern/Sony ZX-1/Pono.

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Sitting room: dCS Network Bridge, 818v3, HD621, 8kSE
Library: dCS Rossini Apex DAC/Clock, Clearaudio Performance Wood, Audio Research PH2, Mjölnir KGST, Mjölnir PureBipolar
SWMBO Room: 210, D33
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Mobile: Audioquest DragonFly Copper, Sennheiser IE600
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Headphones: Stax SR-X9000, Stax SR-007, Stax SR-404LE, Audeze LCD-X...

Oldest audio file: 1889 Edison cylinder