The 4075 filter is a voltage controlled, discrete analog, 24/db/oct cascaded transconductance low-pass filter, employing handmatched transistors. In its lowest FREQUENCY setting it shaves off higher frequency harmonics; its RESONANCE or “Q” circuit pushes those harmonics past the self-oscillation boiling point, projecting a thumpy, thrashing squeal, with explosive low to mid-range power and depth. The design is actually pulled from the four-pole ARP 4072 (better: more parts and trims), sans the 12kHz design flaw which hamstrung the original’s high end. 
The 4075 name has stuck—no correcting our little misnomer. Our 4075 filter is the most requested of the Boomstar filter models, perhaps owing to its uniqueness. Has there ever been a better match for a square wave? It weaves dreams with “glidey,” 70s basslines, is a natural in the lead department, and feels as if a temper tantrum simmers a mere micron beneath its veneer of faux respectability. Aggressive and articulate, this fresh ARP can snap punishing kick drum sounds out as well as color with bright, edgy, stringy tones for essential arpeggiations.