I notice the XLR on the back says "Transister/Bal". Then there is a preamp out which is a 1/4" jack. I assume the XLR is before the pre and the 1/4" is after. For sending a signal to the board, which of these do I use? Not that I need tubes yet, but when the time comes is it safe to assume that I can just put matched sets in and bias it with the screws on back? How are the sets arranged? Sorry for the stupid questions, but it's my first one.