I noticed my Cambridge Audio DacMagic Plus was no longer recognized by my iMac and music was coming out of the built-in speakers instead. I had no idea when the DAC had disappeared, as I hadn’t listened to music in the office for a while (and had been traveling for a week as well). I moved it to another USB port and it was recognized, but the signal it received was at 48 kHz instead of 192 kHz.
- connecting a USB headset to the problem port: it was not recognized.
- connecting the DAC to a Macbook Air: the DAC indicated a 192 kHz signal.
- an SMC reset: no change.
- a PRAM reset: I got the USB port back, but still at 48 kHz.
My searches on Google weren’t turning up anything useful about the sample rate on USB Audio. Then I happened to search for just “imac usb audio 2.0” and started reading the top hit: USB Audio on the Mac. It has a section on Clock Entities showing the Audio Midi Setup tool.
For some reason the Mac had the clock for the external DAC set at 48 kHz. Using the dropdown menu I could set it at 192 kHz and all was instantly back to normal.