After using mine for a few days...just wanted to throw some stuff in, confirm what a few others have said, maybe let some people know that if they're having these issues, they're not alone.
A) Call it hiss, call it noise floor, but it's definitely there with iem's (used shure se535's and vsonic gr07's).
B) If for some reason you're using this as a small desktop dac/amp (This is what I'm doing because I didn't want to use a CCK with my iphone and MFI certified devices are a pain in the ass to find), you can keep the unit charged by plugging the usb into your computer and still playing music from an iDevice through that connection.
- However, even if you don't have your sound device set to the E5 on the computer (I set it back to my laptop speakers at work), things don't quite play right.
-- Every time I get an email or anything else that creates a sound notification on my computer, it causes my phone to vibrate as if I'm getting a text
-- The volume wheel on the E5 ends up controlling the volume on the laptop but not working for the iPhone. Get this, I turned my volume up from the iPhone screen manually and it turned up the volume on my laptop instead
C) Battery drain...others here have said they don't have battery drain issues with iDevices. I've got an iPhone 6. If I plug my headphones into the phone around 6:30 AM and play music nonstop until around time for lunch and I'll end up with about 96% battery left (assuming I charged it on the way in). In the same amount of time with the E5 today, it drained down to 87 percent. But I only listened to music for about an hour and a half to 2 hours during that time. Plugged in but not actually playing it still sucks power.