It's not a low-pass filter, it's a q-filter. The band width is set, as is the amount of boost. What changes as you sweep the knob is the frequency. At the top of it's travel, it's almost up in the dog whistle range. As you sweep it down, the boost becomes lower in frequency. So, unlike a regular passive pot, which IS low-pass (gradually rolls off highs), or the typical bass-treble system, which has SET frequencies but lets you control the amount of boost or cut, the q-filter allows you to pick the frequency you want boosted. The more expensive Alembics (Series I & II) have one for each pickup, and that's where the real fun starts.
This isn't correct - it is a low-pass filter. There is a frequency bump where you have the filter set - on some electronics passes such as the Series I & II, Anniversary and Signature, you can select the amount of boost. So that frequency can be emphasized, but it is still working like a low-pass filter, cutting the frequencies above the point selected.
The SF-2 Superfilter is a rackmount unit where you can select low-pass, band-pass, and high-pass, but the electronics in the Alembics with filters are all low-pass.
) it'll be there.