Re: DSD256 & PCM 24b, 384 kHz on Mac OSX.
I run DSD128 DoP and PCM 24/384 straight out over USB 3.0 on my MBP Retina.
The issue is not data rate capability but, instead, the OSX 'App Nap' battery drain app spanker. The OS puts the Broadcom 20702 USB hub to sleep and the core-audio-bypassing app (Audirvana Plus) has to wake it up. When the number of wakeup events exceed the limit, spin dumps can occur like:
"process Audirvana Plus[2934] caught causing excessive wakeups. Observed wakeups rate (per sec): 178; Maximum permitted wakeups rate (per sec): 150; Observation period: 300 seconds; Task lifetime number of wakeups: 45001"
The AP+ app aserts "App Nap disabled' by default, but I find it helps to send:
"sudo defaults write com.audirvana.Audirvana-Plus NSAppSleepDisabled -bool YES"
All of this is convolved with the "com.Chord.driver.Cypress384 (1.0.55)" USB driver disaster (M2Tech Nova Blowout) which should not be an issue with driverless versions of Chord's newer DACs and/or with OSX 10.10 & 10.11 OS releases. Have to wait to see.
Could also be Apple moving around the KEXT Exceptions Contents directory location....
Main point? Battery life optimization aggressive removes user/signer control over real time I/O.
This may be where the Sound Quality battle is fought. It is not BW, it is power!
