[Fallen]

So, I've just bought a new combo of E17 + E09k which connected through USB to my iMac. Where should my settings be in terms of computer volume vs. volume settings on my E17 vs. volume on my E09K? Which one of these should be maxed out, which one should be carrying the load, etc... 
 
Should my computer and e17 be halfway and let my E09K carry the load through gain and the volume knob? Should my computer volume be maxed out and controlled through the E17 or E09K? Does it make a difference in sound quality either way?
 
I'll be running them to either my Ultrasone HFI-680 and soon my Hifiman HE-400 (Still in the box, wife won't let me open till my birthday. Two more weeks!!!) .
 
Haven't found a definite answer yet, been searching the forums like mad.
 
Can anyone help me out?

 

[PurpleAngel]

With the Fiio E17 docked to the E09K and the E09K connected to the MAC using USB.
Setting the Mac to the highest volume (or as high as possible) and controlling the volume using the E09K's knob should provide the best possible sound quality.

 

[Fallen]

Thanks PurpleAngel!
 
I'm assuming I want to bypass the LOD? The E17 has a switch on the side which lets me do that. When I have the Line Out Dock bypass on, the volume controls on the E17 don't seem to matter anymore.  All volume is controlled by the E09K.
 
I'm assuming that gives a purer signal to the amp. Am I right?

 

[PurpleAngel]

  Thanks PurpleAngel!
 
I'm assuming I want to bypass the LOD? The E17 has a switch on the side which lets me do that. When I have the Line Out Dock bypass on, the volume controls on the E17 don't seem to matter anymore.  All volume is controlled by the E09K.
 
I'm assuming that gives a purer signal to the amp. Am I right?

The E17 DAC should be better then the iMacs DAC (not sure by how much).
So I believe the answer to your question is yes.
 
Personally I would just use the E17 without the E09K.
Connect the iMac's S/PDIF optical output port to the optical input port on the E17,
plug the headphones into the E17's headphone output.