The Tru-Tron 3X™ is the modern all-analog refinement of the classic Mu-Tron III™ envelope-controlled filter. Mike Beigel, the inventor has retained all the mojo that made the 1972 unit so popular is the closest you’ll find to the original Mu-Tronis. The Tru-Tron 3X is the best envelope filter pedal for guitar, bass, keyboards, sax, etc. (original box and paperwork not included), but comes with the power adapter. This unit is in very good working condition (See Photos) We will let this unit go for $3,000.00 plus shipping (US Only) or in store local pick up.