I did experience a max volume blowout when connecting the Gryphon to my iPhone only once. It defaulted to the max volume when changing the input selection settings and reconnecting the DAC to the phone. I could not recreate this from happening again, but I'm sure it could. It's best to disconnect your headphones when changing inputs and manually turning the device volume down when you know it is properly connected before plugging back in your headphones.
Luckily, iFi has released a firmware fix.