Not way off, but not quite precise either. The Klon circuit boosts mids in roughly the 500-800Hz range, with 800 being the middle of the mid range, but it also provides a collective effect that is akin to a slight envelope filtering, not just typical boost. That's why you get just a touch of that vocal 'aww' sound with it. The TS is a more typical boost in the upper mids centered about 1 to 3kHz.
Sorry, man, I don't really talk in terms of "magic", "mojo", or whatever other je ne sais quois, and I can't speak for what others mean when they use those kinds of terms. Envelope filtering uses signal amplitude to sweep a resonance peak filter through the range of frequencies of that signal. The most familiar one might be the auto-wah, where the resonance peak moves to higher frequencies as note volume peaks and vice versa. A wah pedal uses the rocker switch of the pedal to control the filter sweep. A cocked wah is a situation in which the filter is stopped at a particular point in the sweep range. It was common for a period to cock the wah at @ 800Hz to give a very pronounced vocal-like 'aww' sound as an effect for lead playing.
The Centaur circuit (and thus the Soul Food and other Klones) doesn't give a full-on envelope filter effect, but the sound is reminiscent of a somewhat milder version of one, with a very mild but detectable 'aww' character as the gain is dialed up.
I would say about one octave lower than that.The TS is a more typical boost in the upper mids centered about 1 to 3kHz.
No, I am referring to the (small signal) frequency response graph:If you're referring to the article author's spectrograph showing a peak at 440Hz,