Heyo! So I just got an ampeg scr-di. It's really a sweet little box that I'm very happy with, save one thing -- the hiss! When the treble knob is turned up beyond 12, there's a good bit of background hiss (gets louder with more treble). Trying to figure out if my unit is faulty, or if this is par for the course with these guys. Troubleshooting so far: - Running off 9v or power supply, hiss is still there - Changed headphones, basses, still present (it's more like a shhhhh than the hum of single coils) - When pre-amp is off, and signal passes straight through from the input, there is no hiss. Only when the right stomp is on do I hear it. Can anyone who has one of these relate?