The Mi-Si Crystal is designed to retrofit existing passive pickup systems to make them active. It features a battery-free preamp designed specifically to work with undersaddle guitar pickups using passive piezo elements. The preamp for this system uses Mi-Si's custom piezo linearization scheme, allowing for the most truthful and accurate sound from the pickup. Just power up for 60 seconds using the Mi-Si Power Charger, to provide up to 16 hours of performance time