First of all, thank you very much for carefully maintaining this very valuable thread!
Second, I'd like to share some of my thoughts, partly inspired by this thread.
Indeed, the availability of USB digital audio output from android phones has IMO revolutionized the entire approach to portable hi-fi. In fact, I personally tend to see less and less value in expensive portable DAPs (Astrell&Kern, Colorfly and the rest of the pack), since you can instead invest into a higher-class portable USB DAC/AMP, which on average give you a lot more bang for the buck in terms of audio reproduction quality compared to a higher-end DAP. And it allows for a much greater flexibility.
I am a happy owner of a (more or less) typical portable rig: SIII -> USB OTG -> RSA Predator -> Audiotechnica ATH-ES10. And I would have been more than happy with this set up, if not for one terrible annoyance that drives me absolutely mad: this SIII is not a dedicated digital audio transport, but my primary communication device, so I have to take and make phone calls from time to time, and stay connected to the cellular network for that matter, which unfortunately induces terrible hum, beeping sounds and clicks resulting from the device's cellular (mainly) and/or other wireless activity.
The result is a spoiled listening experience, with the only way to stop it (or is it? I didn't found any better way...) is to switch the device to Airplaine mode. This brings in the audiophile nirvana of uninterrupted and unaffected listening, but... undermines my connectivity, which is a critical component of nowadays' on-the-go life.
Heck!!! What to do???
I spent weeks thinking about it, googling all over the place in search for a solution...
I considered dedicated DAPs, and rejected them for two reasons: one, because this would have completely ruin the value of my investment into RSA Predator, the sound signature of which paired to my ES10 I tend to like a lot. But I'd have to either abandon it, or use it as an amp-only, because none of higher-end dedicated DAPs I considered offered usb audio out, and a few had line out bypassing their. Second, I would overpay for the player part of the DAP (storage, processing power, interface, controls, screen) and lose any flexibility of Android in terms of choice of player software/album management etc.
I considered getting a second smartphone with known USB audio out support out-of-the-box to run it as a DAP in Airplane Mode, but my search revealed that I am somewhat limited to higher-end Samsung and HTC models, with bigger and better screens, high processing power etc, which, again, I did not need. The smallest and cheapest I found was Galaxy SIII mini, which still is a 300$ investment in my village.
And then I finally bumped into this thread, and it stroke me: what if I get any cheapest android phone running 4.0 or higher and supporting USB OTG, and USB audio recorder pro will do the rest???
I am sorry for being so long-winded, but do I get it right that in fact ANY android 4.0 or lated devices with USB OTG functionnality will be able to output USB digital audio with the help of USB audio recorder pro??
Your help and advice are highly appreciated!