Just picked up one of these used. Trying to move from 4 string to 5 and ya just gotta love the SR series for playability. Anyway, one of the equalization knobs has an upper and lower part. Top seems to control the high end balance and the the bottom controls the low end. Pretty cool but I'm wondering how this could be stock. Pickups look stock and no signs of any workmanship anywhere. No manuals came with the bass. Anyone else seen this on any SR405 ???? Thanks, in advance, for your reply.