I got a sansamp 3 channel bass driver recently and is doing some tweaking with it. Could any1 tell me what what actually is the presence knob? It sounds like like duplicate of the treble knob to me. The manual says it brings up the "upper harmonic", what does that mean? I'm pairing it with a rickenbacker 4003. Couldn't quite get a satisfying tone at the moment. I play kind of hard to get that slap like tone. It would go too bassy to hear the slap-like tone clearly, or too honky when i try to boost the mids. I almost got the slap-like tone i wanted but it goes too clanky. Seems like 750hz is not a good mid freq to work with in a 4003. Could any ric players give me some suggestions?