Question on your post earlier, if there is no more OTG with USB-C is it just USB Audio? I'm not really sure what the difference is but I knew that USB Audio was baked in to Marshmallow which is why I figured any cable meant for data transfer should work just fine (and has worked, so far).
With new Android devices having USB Type-C connectivity, it is no more relevant to use a USB OTG cable to connect one of these Android devices to a USB DAC, because the ID pin of a so-called USB OTG cable does not exist in the USB Type-C connector (the ID pin is used to determine if the dual-role Android device with a Micro Type-AB receptacle shall be a USB host or a USB peripheral).
However, like the ID pin, the USB Type-C CC pins are used to determine if the dual-role Android device with USB Type-C receptacle shall be a USB host or a USB peripheral according to the USB Type-C Cable and Connector Specification:
. Dual-role Android device with USB Type-C receptacle operating as USB host:
The CC pin of the USB Type-C plug shall be connected to GND through a resistor Rd (5.1 kΩ)
. Dual-role Android device with USB Type-C receptacle operating as USB peripheral:
The CC pin of the USB Type-C plug shall be connected to GND through a resistor Rp (56 kΩ).
So, a dual-role Android device with USB Type-C receptacle should be connected to a standard USB DAC always operating as USB peripheral by one of the following USB Type-C cables:
. USB Type-C to USB Micro-B cable, with the CC pin of the USB Type-C plug connected to GND through a resistor Rd (5.1 kΩ):
dual-role Android device with USB Type-C receptacle >> USB Type-C plug to USB Micro-B plug cable >> USB DAC with USB Micro-B receptacle >> amp >> headphones
. USB Type-C to USB Mini-B cable, with the CC pin of the USB Type-C plug connected to GND through a resistor Rd (5.1 kΩ):
dual-role Android device with USB Type-C receptacle >> USB Type-C plug to USB Mini-B plug cable >> USB DAC with USB Mini-B receptacle >> amp >> headphones
. USB Type-C to USB Standard-B cable, with the CC pin of the USB Type-C plug connected to GND through a resistor Rd (5.1 kΩ):
dual-role Android device with USB Type-C receptacle >> USB Type-C plug to USB Standard-B plug cable >> USB DAC with USB Standard-B receptacle >> amp >> headphones
. USB Type-C to USB Standard-A receptacle adapter, with the CC pin of the USB Type-C plug connected to GND through a resistor Rd (5.1 kΩ):
dual-role Android device with USB Type-C receptacle >> USB Type-C plug to USB Standard-A receptacle adapter + USB Standard-A plug to USB Standard/Mini/Micro-B plug cable (usually provided by the USB DAC maker) >> USB DAC with Standard/Mini/Micro-B receptacle >> amp >> headphones
or
dual-role Android device with USB Type-C receptacle >> USB Type-C plug to USB Standard-A receptacle adapter >> USB DAC with Standard-A plug >> amp >> headphones