I have an Aguilar OBP-3 that I had as an outboard unit, and it worked fine. Yesterday, I decided to install it into a bass. After everything was connected, and installed it had problems. When the midrange pot, or treble pot is moved away from center I get a loud hissing noise. It's a steady hiss, similar to the sound of the TV when it is not receiving a channel. Everything is connected properly, and I checked and double checked. The jack is fine, as well as the volume pot and pickups. When the preamp is bypassed, everything works fine. Any ideas?