Features All-passive tone sulpting circuitry with vacuum tube make-up gain and line drivers Specially-designed filters for Mastering needs Every band switchable to Shelf or Bell All controls stepped and switched for maximum repeatability Custom-wound MANLEY input and output transformers with nickel laminations in mu-metal cases for that big MANLEY sound! Description Product Description This is the Mastering Version of the Massive Passive with innovative repeatable, mechanically detented knobs. Range is clamped down for focus where mastering engineers live and breathe. Filters go higher and lower for final polishing duties.