The Carl Martin TremO'vibe is an analog "two in one" effect pedal consisting of a tremolo and a real vibrato, both with independent sets of speed and depth controls. Now with DC input, no more AC cord. The tremolo effect works like a change in volume. The vibrato, which works as a change in tone (pitch modulation), is carefully designed to imitate the sound of a real tube vibrato. Featuring two switches, The "on" switch allows you to engage or bypass the unit. The "select" switch allows you to switch between Tremolo and Vibrato. The Carl Martin TremO'vibe is an excellent choice for Guitar, Bass, Keyboard, or any other electronic instrument, that requires the highest sonic clarity, maximum dynamic range and noise free performance. Can be used with any 9V DC 200mA power supply, center negative. No battery operation.