In its 'hi-fi' setting, you get a full range boost, but a 'lo-fi' setting offers a more focused boost in one of three frequency ranges controlled with the 3Q switch. Boost in hi-fi mode is bright, with some germanium-driven grit to it, and as you turn the knob clockwise there's a massive amount available. In lo-fi mode, the three settings offer cut in the bottom but different midrange emphasis.
This pedal works best with an amp that's already overdriven, and especially one that's dark-sounding - kick it in to take it up another level and squeeze out some harmonics - it did a fine job with our old non top-boost AC30. It's also great with a dirt pedal.
The Germania can deliver a raw and aggressive boost, but that tonal shift won't necessarily suit all amp settings, so try it out with your own."
You can find the original FSB thread here.