MBox 3 Noise/Hiss from mic

[shank11001]

I'm a new user, so bear with me. I'm running an Mbox 3, iMac snow leopard 10.6.7 trying to record on a Studio Projects C1 mic. When I engage the 48v phantom power and boost the gain, I get a "hiss" I hear on both headphones and monitors. Mic sounds fine, but the hiss is def there even when I back off gain to almost nothing. If I unplug the mic, with the phantom power turned on, the hiss disappears. I've tried different USB ports, no diff. I don't have a way to independently test the mic and cable to isolate the problem.
I should say, it's not a steady hiss, but it seems to vary -- like wind gusting through tree limbs is the best way to describe it. Thoughts?

[Slartibartfat]

Hi! I have the same problem, exactly how you described. Did you fix it in the end?