Pinging sound from Preamp

I just re-arranged my system, and you got it, the audio gremlins have struck. Immediately after start-up mute cycles off on my BAT VK3i, I hear a rhythmic "ping" from the pre and through the speakers. After starting CD, I cannot hear it, then after a while (30-45 min) I start hearing it through speakers over (lounder than) the music (which is at a fairly low volume). When I mute the pre it goes away, and it is present regardless of source selected (even if source is shut off). Any thoughts?