ipods eq is a JOKE.. the BEST settling, believe it or not, is having the EQ turned OFF..
this is what the user that i first saw double amp with the fiio and the z02 told me how to set it up:
"I'm the double amp proponent and love the sound. I go from source (iPhone 4 or 5) out via a Fiio LOD connector to my E-11, then into the ZO, which I set to high gain and highest red bass contour, and into my phones. The E-11 controls the volume.
Done this way, no clipping or distortion, but you have to do it exactly as I have it laid out. Trust me, I tried every other possible way and they all were distorted or worse. You have to use a LOD connector.
The sound depth, bass quality and quantity at low volume levels is what makes this so awesome. Like a subwoofer in your head......"
so i think the fiio is set flat and just used to control volume and by default it cleans up the sound and improves the quality , the z02 is what improves and boosts the bass..