It's observably a piece of junk in many ways, but particularly with sound. The headphone/microphone jack doesn't work most of the time so I have to use usb instead. And at some point the Stereo Mix functionality magically vanished and I cannot bring it back.
It's inability to record audio is probably related.
I also tried recording directly with my phone (iPhone 5s) and my other 3DS, but unfortunately neither of those devices like to use audio input from anything other than their built in microphone.