I am looking for information on what the small 5th knob does on the Ric JK381. Most Rickenbackers that feature a fifth knob use this position to hold a potentiometer that acts, more or less, as a bass/treble balance control. It rotates from full CCW to full CW with no detents. On the JK381, the knob is a 4 position switch. According to the manual, position 1 is Off but the manual does not elaborate on the other three positions. I sent a note to Rickenbacker tech folk but the only info they had was to refer me to the manual, which they kindly re-supplied me.
Any help with this would be gleefully accepted!