Interesting, my 2012 mini has an issue with the new OS. If I put a powered USB hub in-between the BHDAC and the 2012 mini, the BHDAC doesn't drop out at all. Take it away and now it does
. This points to an OS issue with USB power management. Maybe the architecture of the 2009 mini allows for a higher power draw through the USB port. It could be changing the output voltage to lower than 5VDC for a digital signal- possibly small enough to make the BHDAC system unstable. What is the voltage range that the BHDAC can reliably operate within? My guess is that Apple is working towards better power management via the OS overall, so newer machines may likely be effected and old ones will be phased out over time... Likely will be a problem moving forward for all OS(Mac/Win) with evolving systems-right? There is no problem with the BHDAC on my MacBook Pro, Mid 2010 running OS 10.10.3 which is what I was running before the upgrade. I'll upgrade this laptop after making a backup to setup a test system when I have time. I think that I know what the issue is (power management by the OS), but I don't know what the optimal fix will be. I don't like the idea of applying or creating a kludge to fix what should be a simple and efficient system.
FYI-The TOS interface works fine playing directly from the headphone jack out of the 2012 mini- sound is clearly better than passing through the USB hub at 44.1k with iTunes. At higher bitrates, jitter starts in Amarra.
Powercycling for about 10 seconds while keeping the high bitrate fixes the issue without issue. Mediterranean Sundance/Rio Ancho - Al Di Meola, John McLaughlin, Paco de Lucia ; and Cheap Day Return- Jethro Tull sounded fine once the system settled down.