First, with the mic unplugged, check you get 48V between pin2 and pin1 and also between pin 3 and pin1. In this condition do you still get the white noise when the phantom switch is operated?When I use phantom power, I get some loud white noise on my condenser for about 3 seconds. It makes the sound again when I turn phantom off. It doesn't do that on other preamps. Is this reason for concern?