I did a search and my problem didn't come up. However i figure with all the expertise present in these forums, somebody might have an answer...
I recently got an NAD amplifier with a MDC DAC built into it. It sounded great running from my laptop via USB.
When i'm on the move i use a FiioE7 DAC with my headphones. However after i the first time plugged in the Fiio E7 into my laptop via the USB, the laptop was no longer able to recognise the MDC DAC from the amplifier, even after the Fiio E7 is unplugged.
But here comes the strange part: If i plug in both DACs at the same time, after about 30 seconds, the MDC DAC is recognised and works properly again (until is is turned of again, at which point i have to repeat the process to get it working again).
So i suspect there is some kind of interference going on between the two DACs, but is that even possible?
Running windows 7, i have of course already tried installing/unstalling the custom NAD drivers and all.