Whats up fellow lowenders! So I found a 2015 squier dimension 4 string bass on ebay,got the bass for 150 plus shipping...just got it 2 days ago can't put it down now...something I noticed on day two of having it...which is always the day I tear the bass apart and see what makes her work,well, this bass has a 3 band eq and a volume for controls,it's all quick connect wiring ,the pre amp is mounted as part of tge volume knob,then there's 3 plugs for the eq..treble,mid,bass...there's a 4th socket on the pre amp right in line with the others...what's that for ..anyone possibly have an idea?