+1 Freddels. I am assuming that the vintage channel has a traditional Fender preamp where flat is around 2-10-2. The modern/active channel has detents on 5 so I am assuming that 5 -5-5 is flat on that side. Bear in mind that this is all assumption and my settings depend on my bass, the room and my ears as much as anything else. The traditional flat setting is admittedly counter-intuitive but solved a lot of problems for me when I used to own a Mesa 400+ which has the same tone stack.