PT-21 Specifications Input: 1/4" monaural jack (impedance: 1M Ohms) Output: 1/4" monaural jack Power Requirements: AC adapter 9V DC (center minus plug) Current Draw: 20 mA Dimensions: 95mm (D) × 45mm (W) × 55mm (H) Weight: 160g Accessories:Owner"s Manual Main Features Scientific and rigorous tuning program to make tuning more accurate and stable Very small and exquisite True bypassProduct audition:http://www.youtube.com/watch?v=J3HoINjlOik