hey guys, i'm currently using a pair of SD humbuckers on my guitar. 3 way switch. 1 volume/push-pull, 1 tone, and 1 EMG-AB preamp. the push-pull splits the coils. i added the preamp recently to boost the signals of pickups when split, since there was an audible signal loss. the preamp does its job all right, and the wiring info i obtained from EMG's website. but ever since i installed the preamp, there's a loud pop whenever i split the coils via the push-pulls. and there's also 'popping' whenever i switch between pickups. before the preamp was installed, i never had any such problems, even during coil splitting via the push-pull.