About two months ago, I bought a brand new FiiO e7 and e9, along with a new Sennheiser HD650. At first, everything played fine, then I started hearing a small amount of static in my right headphone speaker whenever I adjusted the volume on my e9. Fast forward a month later, and it's much worse. I can hear a LOT of static every time I adjust the volume and it has started to creep into my music too (or perhaps I am just starting to notice it - either way it has definitely increased in intensity).
I believe this problem lies with the e9 because it happens most often when I adjust the volume on the unit. When I increase/decrease volume from Windows, no static happens. Any idea what the problem is?