I have two Warwick Corvettes. One was passive and I had my local tech install MEC golds and a SD STC-2A preamp. Sounds absolutely killer. My other was already active and the preamp was dying. So I bought an STC-3A to have him put it in. 6hrs later he throws his hands up on it saying "its wired up the same as the other...aside from now having a mid pot!" Volume is very low and distorts when plucked hard. The battery in it was only like a week old. I'm posting on his behalf. What could be the issue other than a defective preamp out of the box?