well i have a morely pba-2 dual bass wah. it is completely noiseless when i use a battery but when i try to use a power adapter (it's one of those universal power adapters) it makes a low humming noise in my my amp when it's not in use. i've tried it with different tips, different voltage, and different polarity, nothing seems to make the humming go away unless i use a battery. i've seen on musician's friend they have a power adapter for it. should i get that? and by the way, i know it's not a problem with my amp, so that possiblilty can be exluded. any ideas?