Nick:
Here's an excerpt from a previous post describing how to adjust an SF-2:
I can't say enough good things about the SF-2. While admittedly it was a little daunting when I first got it, seemingly more complicated than I usually like, once I groked it, the SF-2 turned out to be quite simple to set and an amazingly effective tone shaper. When used with in mono mode, it is essentially a 3 channel mixer - one dry channel and two filtered channels. Each filtered channel can be set for low pass, band pass, or high pass. The key is to adjust one channel at a time. (While one is being tweaked, I turn the other two down to 0). First I turn both filtered channels down to 0, turn up the dry channel and set my amp and guitar controls as normal. Then I turn the dry channel to 0 and one at a time, set one filter channel to accentuate a low frequncy I like and the other to accentuate a high frequency. Back to 0 for the filtered channels and the dry channel is turned up, again. Then it's easy to mix in the low and high SF-2 channels to taste. (In stereo mode, it has two channels per side, one dry and one filtered). Once I understood what was happening, the SF-2 revealed itself as a relatively easy to use common sense design.
Bill, tgo