Maybe need to resolder the input jack.  that common issue, especially when using short interconnect.

bukak, then solder.. or give to pro to do.. or claim warranty.

Mine E10 with someone... he 'pinjam' to poison himself.

 

Presume your source is from your PC right 

Obviously you can't connect the gumstick to the E10    While the only way to connect your E11 with your PC is via the headphones output    Looks like the hissing is from both or either of your gumstick / PC and not the E11 

Try connecting the E11 via the lineout of the E10 then to your headphones.  Does it still hiss like before 

Faez,

That type of distortion occurs when the battery is weak, or if you are simply asking too much of a single 9V battery. To drive 250 ohm headphones, dual 9V batteries (18V) are strongly recommended.

Be sure to add a second battery to your shopping cart and mention your DT-880s during checkout. This will give good performance.
Let me know if you have any other questions.

Best regards

Did you try taking the audio from the line out of the E10 to your E11 and see if it still distorts 

E11 on high power mode? (the switch under the battery.)

Beyer DT880 required desktop amp, for sure.

Can't waiting for my E10 to arrive... Stock when you will arrived...

i think someone might be interested in this:

http://www.head-fi.org/t/581048/new-oyaide-hpc-ue-iem-cables

expected release date: 15th December 2011