Because in China, lots of bare boards are not (and will never be) packed with the original cases, they just come out of the factory. You can get one for less than $10 here. It has become a budget choose for many people.
It will get 1v max, the key is when something connect to it, it detects the impedance (or if it is just a cord).
Btw I think External Device means Line Out.
This is how I manage to maintain the high impedance mode:
1.Connect the device to host with USB,
2.Connect ER4B to an extension cable,
3.Connect the extension cable to device,
4.Since the step 3 boots the device, and it keeps working until you detach the cable from the device. So I can detach...
I tried apple dongle which is known to have 1Vrms at max volume, I tested it on iPad with ER4B (about 100 ohm) to compare the max volume with the HIFI plus, and the latter has much larger loudness.
It depends on headphones impedance, AFAIK it has three modes: low(0.3v), line(1v), high(1.8v). I don't know how much impedance could trigger the high mode, it needs more test.
But it's easy to trigger line mode: simply attach an extension cable at first, then connect your headphone to the cable.
Seems like it is limited to 16bit? And if the test could be done without ASIO driver? Or could the settings on the ASIO control panel change something?