Ok, and what setting did you have the Digizoid ZO on? Step 2,... It's not just "on", step "1" step "2". There are numerous settings, so that test is somewhat invalid. That is, unless, you test every step and post the graphs for every one of them. So, the test is incomplete.
The Digizoid ZO starts with a small bass boost, and the last setting is mind-numbing. I found the Digizoid ZO to really sound clean, clear, and HUGE!!! The FiiO E11 is an amp with a 2 stage bass boost. It does sound pretty good, but not D:ZO good.