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According to Android 3.1 specifications, Android devices could support the USB audio feature, i.e. Android devices and USB_CLASS_AUDIO compliant devices like standard USB DAC could interoperate:
USB_CLASS_AUDIO compliant devices like standard USB DAC don't need a special USB device driver. Instead, they use an operating system standard driver.
The Android standard USB audio driver is the generic USB Audio Driver for ALSA (Advanced Linux Sound Architecture).
Android relies on Linux version 2.6 for core system services such as security, memory management, process management, network stack, and driver model. The Linux kernel also acts as an abstraction layer between the hardware and the rest of the software stack.
Thus Android handles all the things that Linux is really good at such as a vast array of device drivers, which take the pain out of interfacing to peripheral hardware.
Most USB DAC work without special USB device driver on PC, Mac and hopefully Android devices with USB audio enabled.
Some USB DAC:
. Portable FiiO USB DAC/amp:
. Portable iBasso USB DAC/amp:
. Portable RSA USB DAC/amp:
. Portable HeadAmp USB DAC/amp:
. Portable GoVibe USB DAC/amp:
. Desktop CEntrance USB DAC/amp:
. Desktop USB DAC MSB DAC IV:
About external USB DAC/Amp
A digital audio system is composed of:
. A storage module: Music is stored in file as a series of bits 0 & 1 with different encoding formats (MP3, WAV, FLAC).
. A player: The player decodes the bits 0 & 1 to PCM digital audio signals.
. A DAC (Digital to Analog Converter): The DAC converts the PCM digital audio signals to the original analog audio signals.
. An amplifier: The amplifier amplifies the analog audio signals.
. A speaker: The speaker restitutes the music.
Like a PC or a Mac, an Android phone is a digital audio system.
Hopefully, the Android phone, running on a kernel with a USB audio driver, can output the PCM digital audio stream to an external standard USB DAC & amplifier & headphone, much more efficient than the internal DAC & amplifier & speakerphone.
The official Android with USB audio enabled should be used by most people, who don't want to mod their device.
A die-hard audiophile minority should likely use audio-optimized Android kernels modded by some kernel modders.
"An interesting example is the HRT music streamer II, it IS asynchronous USB, but it is still very sensitive to what happens in the computer. On the SAME COMPUTER I can make simple changes to OS scheduling parameters and get a huge difference in the sound. At one end of the scale it's dull, lifeless, no depth at all, at the other end of the scale it is wonderfully alive, dynamic, huge depth etc. And all this by just changing a few numbers, NO change in hardware at all."
For example, a underclocked kernel should be better than a normal kernel to provide a lesser jittered digital audio stream to a USB DAC, because the USB transmission clock is less polluted by electric and electromagnetic interferences generated by different processors.
A "modification philosophy":
A list of stock Android-powered devices reportedly interworking with standard USB DAC:
stock Android device > digital USB audio out >> standard USB DAC >> amp >> headphones
A list of standard USB DAC reportedly interworking with the Android-powered smartphone Samsung Galaxy S3:
stock Samsung Galaxy S3 > digital USB audio out >> USB OTG cable (ID pin grounded) >> standard USB DAC >> amp >> headphones
A list of standard USB DAC reportedly interworking with the Android-powered smartphone Samsung Galaxy Note2:
stock Galaxy Note2 > digital USB audio out >> USB OTG cable (ID pin grounded) >> standard USB DAC >> amp >> headphones
A list of standard USB DAC reportedly interworking with the Android-powered smartphone Samung Galaxy S4:
stock Samsung Galaxy S4 > digital USB audio out >> USB OTG cable (ID pin grounded) >> standard USB DAC >> amp >> headphones
A list of standard USB DAC reportedly interworking with the Android-powered smartphone Samsung Galaxy Note3:
stock Samsung Galaxy Note3 > digital USB audio out >> USB OTG cable (ID pin grounded) >> standard USB DAC >> amp >> headphones
A list of standard USB DAC reportedly non-interworking with the Android-powered smartphone Samsung Galaxy S3 / Note2 / S4 / Note3 using USB Audio Recorder PRO / USB Audio Player PRO:
A list of USB OTG cables:
Edited by DanBa - 4/16/14 at 5:05am