400 series 2 hiss

[Dr12volt]

I recently had one of my PL400 series 2 amps start to make a very audible hissing from only one channel. It starts a few minutes after I powe it up. The input sensitivity has no effect on level and it will make this noise even with no input signal connected. Thoughts?

 

[WOPL Sniffer]

Who built it? Isn't it still under warranty? I built one or two a while back and it had a hiss (and WOPL's don't make noise unless you drop them) and it turned out, the Infinity Speakers was causing it. I tested the amp with my Epicures AND my Heresy's and then the Infinity's went up in flames. You know why? Because I chucked them in the burn pit.