From the VFE website:
The TRIUMVIRATE is a unique take on a distortion pedal. The guitar signal is first separated into three pathways (lows, mids, and highs) where the range of each is set via internal trimpots. Next, each pathway goes through its own distortion engine, with full control over the amount of gain in each band. Finally, each band is independently mixed together at the end. In short, the Triumvirate is a multi-band distortion, which works great for guitar, bass, synths, even cellos!
Bass, Treble, Mid (100kA): These are the individual volume controls for each distortion band.
Gain (500kA): These are gain control for the individual bands.
Cut (10k): This trimmer allows you to cut high end from the resulting mix of Bass, Treble and Mid distortion.
Pre (10k): This trimmer increases the input gain before the signal is split into the three bands. Turning it down will decrease the amount of distortion you get across all three and takes it more into overdrive territory.
High (5k, 50k): Sets the low/mid cutoff frequency of the treble band. Use it to add more depth, or to really isolate the treble frequencies.
Low Mid (5k, 50k), Hi Mid (2k, 20k): Sets the frequency of the bottom/top of the mid band. Use it to select the range and width of this band.
Low (5k, 50k): Sets the frequency where the mid/treble start to roll off in the bass band. Pull it back to isolate the lower fundamentals.