From the VFE website:
The WHITE HORSE is an optical compressor pedal and a whole lot more. The blend control allows for longer, sustained notes that aren’t squashed to oblivion. Our unique drive threshold technology allows for touch-sensitive effects, responding to the intensity of your picking and adding grit as you play harder. We’ve included additional controls to fine tune the punch and feel of the compressor to accommodate a wide array of instruments and playing styles.
BLEND: Blends between the dry (uncompressed) and compressed signals. Blend in some clean signal to take advantage of added sustain without overly squashy your dynamics.
SUSTAIN: Adds gain/sustain to the compression stage. There’s a ton of gain on tap, so you won’t need to crank this to the max like all other compressors (though you can if you want).
LEVEL: Sets the output volume of the White Horse. Be careful the White Horse can get LOUD!
PRE-GAIN: Turn it up for more squish & sustain, or pull it back for high input sources (like active bass guitars).
DRIVE: Balances the gain section between the clean compression and a saturated mosfet drive section. Set the SUSTAIN between 2:00-3:00 and DRIVE between 11:00-12:00 for a drive tone that cleans up nicely with playing dynamics. Don’t forget to cut some of the bass to tighten up your drive tones!
BASS: Sets the speed at which the compressor reacts to your playing dynamics. Pull it all the way back for a snappier attack, or pull it back to smooth out the sustain at high compression settings.
SPEED (“Response” on schematic): Sets the pre-gain bass cut. Due to the way the human brain hears different frequencies, it is often helpful to cut a touch of bass in compression. Crank it to the max for a flat bass response.