Found the following over on BGRA - may have some perspective...
"Bartolini:
"NS2TMB-183", 18 Volts. Bass
This is Bill Bartolini's latest and most refined design. It is quieter and more transparent than anything else out there (108 dB S/N, THD .003% @ 100Hz) and really sounds good. To quote from the spec sheet "The (bipolar) +9V/ -9V system allows a completely DC coupled signal path. There are no capacitors to diminish in any way the low end punch, clarity and frequency response of the instrument". Bill has used wide bands that overlap slightly to avoid the honky sound of other midrange controls. The 250Hz mid could be useful as a cut option when recording."
Now all we need to know are the benefits of a completely DC coupled signal path :-)