[kirkmc]

I just bought a Sennheiser RS 180 wireless headphone. I was looking forward to listening to music wirelessly from my Mac, which is connected to a DAC > Amp, and controlling it with my iPod touch in different parts of my home. 
 
Alas, there is a very loud hiss on the headphones; which, considering that the many reviews I've read say doesn't exist, is surprising. I've tried turning off all my other wireless devices - wifi and phone - and the hiss is still there.
 
I would have like to contact Sennheiser to see what they suggest, but they don't offer any support (I'm in France; this may differ in other countries). 
 
Before I send them back to Amazon, are there any suggestions as to what I should look at to get rid of the hiss? Has anyone else had this problem?

 

[mark2410]

erm maybe you have the headphones themselves turned up full? are you running the input really quietly?
 
could be your source is just producing a lot of hiss

 

[kirkmc]

No, my source is clean; with other headphones, there's no noise.
 
Altering the volume did alter the level of the hiss, but at normal volume, the hiss was notable.

 

[mark2410]

are you sure its at normal volume?  that the input volume isnt really low thus requiring the headset whacked up full?
 
if thats not the case then you have buggered pair or something broken along the line

 

[stokitw]

Make sure you find a good match between the source volume and headphone volume.
Try to turn up or down the source volume and adjust the headphone volume accordingly.
 
Even with digital transmission, finding a adequate source volume is still the key of audio quality for wireless phones.
 
Quote:

No, my source is clean; with other headphones, there's no noise.
 
Altering the volume did alter the level of the hiss, but at normal volume, the hiss was notable.