Have become very interested in filters. Marlon Reed's DP 4-string has an Alembic PJ Activator circuit in it. Loved the sound, very "attacky." Interesting, when you turn the "tone" knob, it sounds like a wah, a very strong effect compared to your garden-variety tone pot. The idea is the pot changes the frequency of the low-pass filter's very steep roll-off. The Alembic site says they feel this filter is more the way acoustic instruments work. Asked Alembic about the optional boost switch, they said it defeats the normally-on boost (which I was unaware of). The boost puts an 8 dB hump right before the roll-off point. Alembic said that turning off the boost is a gentler, more natural sound, and that many players who start off using lots of boost eventually turn it off for more and more tunes and some quit using it altogether. I have read many comments that Alembics sound kind of brash or metallic, and I'm guessing that's the reaction to the boost. Alembic said their higher-end basses offer more options on how to handle the filter, like individual filters per pickup and continuously variable boost, and that their Superfilter (SF-1) rack unit offers the most flexibility and also the greatest potential for making truly ugly sounds if you don't watch it. I love the super attack, but I like the idea of the softer sound, too. And yeah, tone pots just don't roll off the highs the way I want, either they retain too many of the highs or they sound mushy. I guess I've always really wanted to pick the frequency I start to lose highs at, not to just reduce highs in general, so I just had to have a low-pass filter, but I wanted a 5-string P pickup, not a soapbar, and Alembic says they haven't made a P5 pickup since the late 70s. I ended up getting a NOS Bartolini EZQ filter off eBay that I'm having Dave set up with the continuously-variable boost pot (this costs 6 dB gain over the 0/+8/+20 boost switch, however if you have one tone pot hole and don't want to make more, either for a pot or a switch, you could just wire it up for 0 or +8 boost). My unit is the 10-wire one without the bass boost; I want to find a 13-wire one also to play with. Anyway, if you are like me and you never really liked the standard tone knob (I don't much care for T/B or T/M/B controls either for the same reasons), maybe you're a candidate for a low-pass filter. Alembic says lots of folks opt for the T/B knobs instead of the filter, it's a more familiar thing and lots of folks can't get their heads wrapped around the filter concept, but to me, it's a lot more natural, useful, and musical than treble bleed or normal EQ.