Hi all, I'm trying to install a John East preamp into a passive bass. It's grounded/shielded with copper in the whole cavity. After install, the preamp/active is not engaging. It works passive through and with this install just fine. I've spent an hour making sure the battery is providing 9v. When I engage the active, NOTHING. But when I pull the tone knob, I get a full signal. When I test the battery (both at source and in circuit), it registers proper 9v. I'm not sure what to try next. Has anybody out there dealt with this issue? Please advise.