In the meantime, we could analyse your Geek Out-S4 dmesg output log file,
and the USB descriptors of the Geek Out using USB View.
The analysis could be proceeded as following: compare a dmesg output issued from a successful Android device - USB DAC interworking (i.e. S4 - FiiO E18 dmesg output) to a bugged dmesg output (i.e. S4 - Geek Out dmesg output).
The USB errors of a dmesg output are listed at the following links:
It's weird because the Geek Out 1000 can work with a S5 or a Note3 without using a USB hub.