Four-channel amplifier with integrated battery recharging system for the emergency power supply to the VARIODYN D1 Comprio. The 4XD250B features 4 independent amplifier channels, each with 250 W, in class D direct drive technology. Due to the fact that all amplifier channels are completely independent from each other, it is possible to use one channel for back up. This could be for the other 3 channels or alternatively for other amplifier channels of other amplifiers with the same or lower output power (only 4XDxxxB and 4XDxxxW models). The amplifier can be used in combination with the VARIODYN D1 Comprio as well as with a DOM. It is also possible to use the amplifier also with a separate PSU, the internal PSU must be switched of then. In this case the internal battery charger must be disabled.