USB Class 2 mode.
Posted by: Got Hi-Fi? on 12 June 2017
Is anyone here running a Cambridge Audio DAC in class 2 mode?
I am currently streaming Tidal from a MAC mini > CA 851D DAC > 202. It works perfectly fine in USB Class 1 mode. However, when I flip it to Class 2 .. I get nothing but white noise. Anyone have any similar issues?
I will more than likely just run it optical anyways as I don't hear a difference between USB audio and TOSlink, but I would still like to know what is causing the issue.
Posted on: 12 June 2017 by Mac User
Have you re-configured the MAC mini after switching, it's not automatic?
Posted on: 12 June 2017 by Got Hi-Fi?
What would need to be reconfigured? According to CA, it is automatic for MACs.
Posted on: 12 June 2017 by Mac User
You'll have to re-select the "new" DAC in the MAC mini setup each time you switch?
Posted on: 12 June 2017 by Got Hi-Fi?
It always showed up as 2.0 regardless of which setting the DAC was on, so I didn't have that choice.
Posted on: 12 June 2017 by Got Hi-Fi?
Maybe I need to reboot the MAC after switching. I will have to give that a try.
Posted on: 12 June 2017 by Mac User
Next is the Audio MIDI setup, then select the Sample Rate...
Posted on: 12 June 2017 by Got Hi-Fi?
The sample rate changes automatically, but I did play around with that too just to make sure, and it made no difference.
Posted on: 12 June 2017 by Got Hi-Fi?
Thank you for the info MAC USER, after rebooting, then selecting the Class 2 version of the DAC, my static has gone away.
I do have one question about the sample rates though .... on USB Class 1 the display on the DAC changes automatically from 44.1 to 88.2 or 96 depending what I stream, as it does on the MAC. However, in Class 2 mode, it does not change. I have to manually set it. Do you know if that is normal?
Posted on: 12 June 2017 by Mac User
Your observations are fairly typical for changes between Class 1 and Class 2 usage and it is all about the signal the DAC receives. There are third party apps like BitPerfect for the MAC that can help with auto switching or a more expensive option is Audirvana. I can't personally confirm either will work with your DAC but I have used both in the past with alternative DACs.
I hope you enjoy your new setup. 
Posted on: 13 June 2017 by Got Hi-Fi?
Thanks again. CA has also confirmed what you mentioned above, they recommended bitperfect to change the mac in class 2 mode. However, I am planning to get audirvana, so maybe I will wait on that one. Thanks again for all the help!
Posted on: 18 June 2017 by Got Hi-Fi?
Finally got my Audirvana license and all is well. The auto switching in USB Class 2 mode is working
