I own the fiio e11 and soundmagic e10. Just got them about 2 weeks ago. I have tried the fiio e11 with my panasonic rp-htf890 and it works perfectly (very minimal hissing). Its impedance is 50 Ohm. However when using the fiio e11 with soundmagic e10, there is more hissing particularly on the right channel when EQ 1 and 2 are used: sounds like some variable wind tunnel - even on low power mode and low gain. This problem only happens when EQ1 and 2 are on, and is non-existent at EQ0. It also only happens on the right channel of the earbud. This is a small sound but it's definitely noticeable. Not as noticeable to unnoticeable when music is playing but when the music is paused, it's audible. I guess it's tolerable because it's a small sound. Can anybody check the E10 with the Fiio e11 for this? Cell phone and laptop both used to test this for me. I'm considering returning E10's for something of similar price range. Wondering if my particular E10 could be defective? Anybody know how to solve this?