So a friend of mine got his hands on a Digitech Bad Monkey Tube, and he says the pedal doesn't work with his Jackson JS3V Concert QS, but it does work with his shitty Stagg (don't know the model). When he connects the Jackson to the pedal there's no bass sound, only noise. He says the cable is fine.

Any idea what might be the problem?
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If the cable is fine it must be the bass. If the bass works fine ithout the pedal in the chain, and the pedal works fine using the same cables with a different bass, then he has a poltergeist.
Spare a Cow
Eat a Vegan
Well his house is a bit old, but I don't think he has a poltergeist or anything. Any other ideas?
I have no sig
Here's a long shot but I really can't think of anything else.

He might be using a stereo cable and either the left or right side connection of his Jackson isn't working; the Bad Monkey might be a mono pedal and only picking up the side that isn't working.

I'm assuming he's checked the Jackson clean?
it has nothing to do with active or passive. theoreticaly it should work all fine, keep looking for the problem, as our forum mates adviced above. same cable, same jacks, just switch instruments. you'll find it eventually. maybe a damaged conection?