Android USB Audio

[tomrisky]

Hello, all!

I read tons of forums on the topic of USB Audio on Android phones like this one: Android phones and USB DACs, or this one: Enable USB audio on any Android 4.0 device, and I am still very confused. I was wondering if someone knowledgeable could clear up my understanding of the issue.

Here's my understanding:

1) The device has to have hardware USB OTG support. Galaxy S3 has it. What about S2? If I can connect an external harddrive or a mouse to my phone and it works, it means basic hardware USB OTG support is present, correct?

2) Kernel has to be compiled with USB Audio support. Which kernels are available that has this feature?

3) Then there are posts saying that 4.1 Jelly Bean has USB Audio support - Android 4.1 FINALLY USB Audio. Does that mean that any device > 4.1 should be able to play USB Audio out of the box? Should my S2 work with any USB Audio device if I flash Jelly Bean on it?

4) But then the Google Code issue (Issue 24614 - android - Enable USB audio on the Galaxy Nexus (or any Android 4.0 device) - Android - An Open Handset Alliance Project - Google Project Hosting) is still open. What does it mean? What exactly happened in 4.1 in regards to USB Audio?

5) Some devices like Galaxy S3 support USB Audio out of the box. But some amplifiers like E17 do not work with them even though they're supposed to. E17 has a hardware issue which other amplifiers do not have. Is this roughly correct?

6) How exactly should it look like when it's working? Do I just connect the device and after some delay, all sound is redirected to the external device? Or there's some option somewhere to do it, or an app?

7) Any information whether Nexus 4 has USB Audio working out of the box?

Thank you very much for your help!

Regards,
Artem.