Originally Posted by fnordlyone
It is a bit weird; if I put my and on any of the knobs, the hiss becomes much more quiet. Has anyone else experienced this? Frankly, the hiss drives me crazy; maybe it's a grounding issue as it seems to stop when i touch the knobs?
Usually it's hum that goes away when you touch ground (metal knobs, jack, strings, etc.) An that means your bass needs more shielding.
But in your case, you describe it as "hiss" since the bass is passive, it has to be basically the same thing only there is something in the room creating a "hiss" as electrical noise (high frequency computer power supply?) rather than the usual hum. Fix is still the same. Copper foil shield job.