Rocktron Texas Recoiler - Manual (Page 8)

Rear PCB Bandwidth Adjustment Pot
REAR PCB POT: Use this to adjust the Band Width of the
Windings Filter. This will adjust how narrow or wide the dip
effect becomes. Set it up the way you like it and you are ready
to rock!
To access this pot, remove the back cover and adjust the pot
with a screw driver. Set the pot as desired to achieve the best
sound to suit your needs.
In the photo below is a drawing of the where the pot is located
on the PCB board. Note, be careful not to over turn the pot in
either direction.