[sniperwill0]

Hello all. For a good while now, I've been hearing this hissing sound coming out of the right ear of my HD 558s. It gets louder when I turn my volume knob on my amp (Schiit Magni) down, and is the loudest when the knob is turned down all the way. The hissing goes away if I turn my volume up to a certain level. Also, the pitch of the sound rises and falls when I move my headphone cable up and down. My amp is coupled to my DAC (Schiit Modi), which plugs into my computer via USB. Not sure what's wrong, any ideas?

 

[Koss02]

check your grounding on the DAC / AMP you have.  Or make sure there isn't any interference (cables, bad outlet? etc..)
 
to see if the problem lies in your headphones or DAC/AMP, try plugging your headphones into another device.  

 

[sniperwill0]

It could be interference. There is quite a bit of cabling around my computer (speakers/sub/monitor cable/extension board etc.) 
 
I can't really try them on another device as they have a quarter inch jack unfortunately. Although, when I plug in my IEM's, the noise is gone.