Subdecay Prometheus DLX Resonant Filter for Guitars The most versatile filter pedal on Earth just got better! While the options are nearly infinite, we made sure to keep things simple enough so that the average guitar player could figure them out in a few minutes. Powered by an external regulated 9VDC to 18VDC adapter with a negative center 2.1mm barrel style plug. The Prometheus DLX is hand made in Oregon. 3PDT switches for true bypass switching.