I've had my 4HH for more than a year now, and it is my main bass. But just figured this out this past weekend -- This bass (with three-channel preamp) should come with a label on the front that reads:
"The three channel preamp works as follows:
Low - controls the volume of the E and A strings.
Mid - controls the volume of the D and G strings.
High - controls the amount of sibilance.
WARNING: Attempting to set the lows and mids too far out from each other will result in an inbalance in string-to-string volume.
WARNING: Setting the lows too high will cause all resonant items within striking distance to rattle and resonate to the point of fearing destruction!!"

"The three channel preamp works as follows:
Low - controls the volume of the E and A strings.
Mid - controls the volume of the D and G strings.
High - controls the amount of sibilance.
WARNING: Attempting to set the lows and mids too far out from each other will result in an inbalance in string-to-string volume.
WARNING: Setting the lows too high will cause all resonant items within striking distance to rattle and resonate to the point of fearing destruction!!"