I've got a fairly bare portable setup consisting of Itouch 5g, digizoid ZO 2.3, three headphones ( HD439, FC300, Dolphin)
Recieved the dolphin headphones yesterday, did the foam removal mod before i even listened to em and they sound really similar to the FC300's.
Maybe ten minutes into listening to them, the sound just went low outta nowhere, never happened before. Started fiddling around with the cables, volume still low. Turned on/off the ZO, still low. Removed the ZO from the setup and the volume level returned to normal??? This never happened with my other headphones.
Later on after letting it burn i a bit with white/pink noise, I listened to them again. Fine for a while then low volume again. Put the ZO in low gain mode(blue) and haven't had that problem since.