До сих пор ищу решение проблемы - наткнулся на такую беседу:
I'm having real trouble playing audio through my DAC and headphone amp (Schiit Magni and Modi). If I plug in the DAC, sometimes it is recognized in the USB tree, sometimes it is not. If I have the audio device system preference window open, I can watch it appear and disappear. It will begin to play, and then it will hiccup and switch back to internal speakers and back and forth rapidly even though the menu bar icon remains dimmed with the Schiit selected. Eventually I have to give up, disconnect everything, and go with the internal speakers.
If I try to play Spotify audio, the application often stalls stating that "this track cannot be played", and then it won't start even if I unplug the DAC.
I cannot remember when this started, but I believe my usb issues (audio and other accessories failing to be recognized) began with my first El Capitan update.
I'm having a similar problem with my brand new Schiit Audio Bitfrost Multibit DAC. I can watch in the Audio Midi Setup utility as the DAC appears and then disappears repeatedly until it finally stops showing up altogether. The curious thing is, this kind of behavior only happens when I'm connected to the left hand side USB port on my 2014 MBP. When I connect the DAC to the USB port on the right hand side it works perfectly fine. So, trying a different USB port may be a quick fix, as it was for me.
When I visited the Schiit Audio website for some troubleshooting info, they mention the poor port power management inherent in Mavericks, Yosemite and El Capitan as a potential source of the problem. Emailing their tech support, they suggested connecting an external USB 2.0 hub to see if that might potentially alleviate the issue. I have not done that yet. Schiit Audio also sells a USB device called Wyrd for $99 that is apparently a "USB decrappifier" (their words) that you connect between the DAC and the computer to clean up the noisy USB power problems which might also solve the problem. When I have the $$ I'm going to buy one and see if it makes a difference.
...из чего сделал вывод, что до Эль капитан всё было в порядке.
И ещё, Shiit продаёт на своём сайте фильтр USB сигнала Wyrd. И вот мне интересно - эта штука реально работает или это "развод на бабло"