Line stereo/2-channel recording

Question

Are there any Android devices available that support multi-channel (stereo) recording via line-in?

With the devices I tested (Nexus 4, HTC Buzz, Motorola Xoom ..), i

Answer 1

Are there any Android devices available that support multi-channel (stereo) recording via line-in?

Concerning most smartphones and tablets factory-equipped with Android there is an unpleasant answer: No.

Why not? Because these devices (and BTW also all iPhones) use the 4pin TRRS-3.5mm-plug to connect headphones and/or microphone to the device. The four pins are used for T) left speaker, R1) right speaker, R2) ground for speaker and microphone, and finally S) monophonic microphone.

UPDATE: When I added in Dec 2013 that "the invention of the TRRRS (I would suggest to call it "T3RS") plug would solve the problem" I couldn't know that Sony was already working on that and presented the "STM-10" stereo microphone with exactly that T3RS-plug in Feb 2014.

Is this a gerneral limitation

Yes, but simply due to the hardware audio plug, not due to licensing.

In 2014 there came very few Android smartphones that have the T3RS-plug with external stereo input: Xperia Z2, Z2 tablet, Z3

As a side note, the gain of the input amplifier is adjusted to microphone output level and not to line level (e.g. of a CD-player).