My source is my computer. Dunno if the sound card is any good really. I did just get some SR-60s, so the FX-33s are for travel, because they isolate pretty well. The hiss just bugs me a bit. It is out of both channels.
Any chance you could describe the hiss? Is is continuous no matter what you're listening to? Or a certain frequency range? What I'm thinking is that adding a little more foam when doing the kramer mod might fix the hiss. I noticed a little sibilance when I did the kramer mod, so I added more foam and that fixed it right up.
perhaps the fx33's don't have enough impedence on them?
they hiss when i use my computer, but when i used a pair of ksc75's, there was no hiss to be found with the computer. also there is no hiss with either when using both on my mp3 player.