I just sold my ts9b because it didn't sound quite as good with a JB as it did with my Squier Vintage Modified P-Bass TB. I think it has to do with the low end the P-Bass already had with it. It worked awesome with the P-Bass TB (just a humbucker at the neck) though, specially with a CS2 before it to get a hot signal even before reaching the ts9b.
And if it helps, i have an Art MPA II Preamp with JJ ECC83-S tubes and the TS9b just sounded like hot tubes. The Mix knob is a blessing, too, imo.