3 leaf Proton Envelope Filter - Matte Black Oxide

3 Leaf Audio Proton MK4 – Matte Black

The Altitude Summary

This U.S.-made Proton MK4 envelope filter, hand-built in Seattle, WA between 2020 and 2025, is in excellent condition with only light scratching on the bottom—nothing visible once it’s on your board. Fully functional and gloriously expressive, this filter is an instant creativity booster. With true bypass and refined circuitry, it delivers all the envelope snap, sweep, and funk you could ever want. A fun, musical pedal that rewards nuance and lets your tone breathe.

Touch-Sensitive Funk in a Box

The Proton MK4 is engineered for feel. Dig in and get rich, vocal sweeps—or back off for more subtle motion. It nails the envelope filter sound with a balance of warmth and punch, always reacting with player sensitivity in mind.

Updated for Modern Players

This fourth-gen version features improved headroom, reduced noise, and enhanced responsiveness. Whether you're running passive bass, hot pickups, or synths, it keeps up effortlessly without flattening your dynamics.

Built for Boards and Stages

Wrapped in a tough matte black enclosure, this Proton MK4 is sleek and sturdy. True bypass means your core tone stays intact when the filter’s off, and the small footprint makes it a perfect fit for tight pedalboards.

Key Features

• Made in Seattle, USA
• Production years: 2020–2025
• Matte Black finish
• Fourth-generation Proton circuit
• Dynamic, responsive envelope filter
• Improved headroom and noise performance
• True bypass switching
• Minor cosmetic wear on bottom only