It's either a dodgy pedal, they are all old now, or its the gain from your active. Maybe the pick ups are hotter and more 'hi-fi' than the pedal can handle. Which, especially if your using high levels on the high compression side, could be making it hiss loads. The pedal's not a true by pass pedal either.
I can only suggest bringing down the volume knob on the bass (boosting the volume on the amp to get the loudness you need) and using little, if any, high compression. Other than that, yeah, time for a new pedal. Check out these reviews - great site: [url="http://www.ovnilab.com/"]http://www.ovnilab.com/[/url]
Try to check the pedal with a low output bass and nothing else in the chain because if its not the pedal ie it just can't handle your set up at least you can sell it as a working one.