The Mi-Si Acoustic Trio System features an active, battery-free preamp
designed specifically to work with the L.R. Baggs undersaddle Element
acoustic guitar pickup. The preamp for this system uses Mi-Si’s custom
piezo linearization scheme, allowing for the most truthful and accurate
sound from the
pickup. All you have to do is power up for 60 seconds using the Mi-Si Power Charger, providing you with up to 16 hours of performance time.